Urinary System

General Structure and Functionsof the Urinary System

The kidneys filter waste products from the bloodstream and convert the filtrate into urine

The ureters urinary bladder and urethra are collectively known as the urinary tract because they transport the urine out of the body

Functions of the Urinary System

Removing waste products from the bloodstream Storage of urine The urinary bladder is an expandable muscular sac that can store as much as 1 liter of urine

1048708 Excretion of urine 1048708 Blood volume regulation

ndash the kidneys control the volume of interstitial fluid and blood under the direction of certain hormones

1048708 Regulation of erythrocyte productionndash as the kidneys filter the blood they are also indirectly

measuring the oxygen level in the blood

Blood Supply to the Kidney

Blood plasma is filtered across the glomerulus into the glomerular space

1048708 Once the blood plasma is filtered blood leaves the glomerulus and enters an efferent arteriole

1048708 Note that the efferent arteriole is still carrying oxygenated blood because a gas and nutrient exchange with the kidney tissues has not yet occurred

Blood Supply to the Kidney

The efferent arterioles branch into one of two types of capillary networks

ndash peritubular capillaries orndash vasa rectandash these capillary networks are responsible for the actual

exchange of gases and nutrients 1048708 Peritubular capillaries primarily reside in the cortex

of the kidney Vasa recta surround the thin tubes that project into

the medulla

Nephrons

The functional filtration unit in the kidney Consists of the following components

ndash a renal corpuscle a proximal convoluted tubule ndash a nephron loop and ndash a distal convoluted tubule and are collectively known as the

renal tubule 1048708 Together both kidneys house approximately 25

million nephrons 1048708 These microscopic structures measure less than 5

centimeters in total length

Proximal Convoluted Tubule

The proximal convoluted tubule originates at the tubular pole of the renal corpuscle

1048708 The cells of the proximal convoluted tubule actively reabsorb almost all nutrients (glucose and amino acids) electrolytes and any plasma proteins from the tubular fluid

1048708 Approximately 60 to 65 of the water in the tubular fluid is reabsorbed by osmosis

1048708 The solutes and water are returned to the vascular system via the peritubular capillaries

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

General Structure and Functionsof the Urinary System

The kidneys filter waste products from the bloodstream and convert the filtrate into urine

The ureters urinary bladder and urethra are collectively known as the urinary tract because they transport the urine out of the body

Functions of the Urinary System

Removing waste products from the bloodstream Storage of urine The urinary bladder is an expandable muscular sac that can store as much as 1 liter of urine

1048708 Excretion of urine 1048708 Blood volume regulation

ndash the kidneys control the volume of interstitial fluid and blood under the direction of certain hormones

1048708 Regulation of erythrocyte productionndash as the kidneys filter the blood they are also indirectly

measuring the oxygen level in the blood

Blood Supply to the Kidney

Blood plasma is filtered across the glomerulus into the glomerular space

1048708 Once the blood plasma is filtered blood leaves the glomerulus and enters an efferent arteriole

1048708 Note that the efferent arteriole is still carrying oxygenated blood because a gas and nutrient exchange with the kidney tissues has not yet occurred

Blood Supply to the Kidney

The efferent arterioles branch into one of two types of capillary networks

ndash peritubular capillaries orndash vasa rectandash these capillary networks are responsible for the actual

exchange of gases and nutrients 1048708 Peritubular capillaries primarily reside in the cortex

of the kidney Vasa recta surround the thin tubes that project into

the medulla

Nephrons

The functional filtration unit in the kidney Consists of the following components

ndash a renal corpuscle a proximal convoluted tubule ndash a nephron loop and ndash a distal convoluted tubule and are collectively known as the

renal tubule 1048708 Together both kidneys house approximately 25

million nephrons 1048708 These microscopic structures measure less than 5

centimeters in total length

Proximal Convoluted Tubule

The proximal convoluted tubule originates at the tubular pole of the renal corpuscle

1048708 The cells of the proximal convoluted tubule actively reabsorb almost all nutrients (glucose and amino acids) electrolytes and any plasma proteins from the tubular fluid

1048708 Approximately 60 to 65 of the water in the tubular fluid is reabsorbed by osmosis

1048708 The solutes and water are returned to the vascular system via the peritubular capillaries

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Functions of the Urinary System

Removing waste products from the bloodstream Storage of urine The urinary bladder is an expandable muscular sac that can store as much as 1 liter of urine

1048708 Excretion of urine 1048708 Blood volume regulation

ndash the kidneys control the volume of interstitial fluid and blood under the direction of certain hormones

1048708 Regulation of erythrocyte productionndash as the kidneys filter the blood they are also indirectly

measuring the oxygen level in the blood

Blood Supply to the Kidney

Blood plasma is filtered across the glomerulus into the glomerular space

1048708 Once the blood plasma is filtered blood leaves the glomerulus and enters an efferent arteriole

1048708 Note that the efferent arteriole is still carrying oxygenated blood because a gas and nutrient exchange with the kidney tissues has not yet occurred

Blood Supply to the Kidney

The efferent arterioles branch into one of two types of capillary networks

ndash peritubular capillaries orndash vasa rectandash these capillary networks are responsible for the actual

exchange of gases and nutrients 1048708 Peritubular capillaries primarily reside in the cortex

of the kidney Vasa recta surround the thin tubes that project into

the medulla

Nephrons

The functional filtration unit in the kidney Consists of the following components

ndash a renal corpuscle a proximal convoluted tubule ndash a nephron loop and ndash a distal convoluted tubule and are collectively known as the

renal tubule 1048708 Together both kidneys house approximately 25

million nephrons 1048708 These microscopic structures measure less than 5

centimeters in total length

Proximal Convoluted Tubule

The proximal convoluted tubule originates at the tubular pole of the renal corpuscle

1048708 The cells of the proximal convoluted tubule actively reabsorb almost all nutrients (glucose and amino acids) electrolytes and any plasma proteins from the tubular fluid

1048708 Approximately 60 to 65 of the water in the tubular fluid is reabsorbed by osmosis

1048708 The solutes and water are returned to the vascular system via the peritubular capillaries

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Blood Supply to the Kidney

Blood plasma is filtered across the glomerulus into the glomerular space

1048708 Once the blood plasma is filtered blood leaves the glomerulus and enters an efferent arteriole

1048708 Note that the efferent arteriole is still carrying oxygenated blood because a gas and nutrient exchange with the kidney tissues has not yet occurred

Blood Supply to the Kidney

The efferent arterioles branch into one of two types of capillary networks

ndash peritubular capillaries orndash vasa rectandash these capillary networks are responsible for the actual

exchange of gases and nutrients 1048708 Peritubular capillaries primarily reside in the cortex

of the kidney Vasa recta surround the thin tubes that project into

the medulla

Nephrons

The functional filtration unit in the kidney Consists of the following components

ndash a renal corpuscle a proximal convoluted tubule ndash a nephron loop and ndash a distal convoluted tubule and are collectively known as the

renal tubule 1048708 Together both kidneys house approximately 25

million nephrons 1048708 These microscopic structures measure less than 5

centimeters in total length

Proximal Convoluted Tubule

The proximal convoluted tubule originates at the tubular pole of the renal corpuscle

1048708 The cells of the proximal convoluted tubule actively reabsorb almost all nutrients (glucose and amino acids) electrolytes and any plasma proteins from the tubular fluid

1048708 Approximately 60 to 65 of the water in the tubular fluid is reabsorbed by osmosis

1048708 The solutes and water are returned to the vascular system via the peritubular capillaries

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Blood Supply to the Kidney

The efferent arterioles branch into one of two types of capillary networks

ndash peritubular capillaries orndash vasa rectandash these capillary networks are responsible for the actual

exchange of gases and nutrients 1048708 Peritubular capillaries primarily reside in the cortex

of the kidney Vasa recta surround the thin tubes that project into

the medulla

Nephrons

The functional filtration unit in the kidney Consists of the following components

ndash a renal corpuscle a proximal convoluted tubule ndash a nephron loop and ndash a distal convoluted tubule and are collectively known as the

renal tubule 1048708 Together both kidneys house approximately 25

million nephrons 1048708 These microscopic structures measure less than 5

centimeters in total length

Proximal Convoluted Tubule

The proximal convoluted tubule originates at the tubular pole of the renal corpuscle

1048708 The cells of the proximal convoluted tubule actively reabsorb almost all nutrients (glucose and amino acids) electrolytes and any plasma proteins from the tubular fluid

1048708 Approximately 60 to 65 of the water in the tubular fluid is reabsorbed by osmosis

1048708 The solutes and water are returned to the vascular system via the peritubular capillaries

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Nephrons

The functional filtration unit in the kidney Consists of the following components

ndash a renal corpuscle a proximal convoluted tubule ndash a nephron loop and ndash a distal convoluted tubule and are collectively known as the

renal tubule 1048708 Together both kidneys house approximately 25

million nephrons 1048708 These microscopic structures measure less than 5

centimeters in total length

Proximal Convoluted Tubule

The proximal convoluted tubule originates at the tubular pole of the renal corpuscle

1048708 The cells of the proximal convoluted tubule actively reabsorb almost all nutrients (glucose and amino acids) electrolytes and any plasma proteins from the tubular fluid

1048708 Approximately 60 to 65 of the water in the tubular fluid is reabsorbed by osmosis

1048708 The solutes and water are returned to the vascular system via the peritubular capillaries

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Proximal Convoluted Tubule

The proximal convoluted tubule originates at the tubular pole of the renal corpuscle

1048708 The cells of the proximal convoluted tubule actively reabsorb almost all nutrients (glucose and amino acids) electrolytes and any plasma proteins from the tubular fluid

1048708 Approximately 60 to 65 of the water in the tubular fluid is reabsorbed by osmosis

1048708 The solutes and water are returned to the vascular system via the peritubular capillaries

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Nephron Loop

The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule and projects internally toward and into the medulla

1048708 Each loop has two limbs ndash descending limb extending from the cortex toward

and into the medullandash ascending limb returns back to the renal cortex

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Distal Convoluted Tubule

The distal convoluted tubule originates in the renal cortex at the end of the thick ascending limb of the nephron loop adjacent to the afferent arteriole

1048708 The primary function of the distal convoluted tubule is secretion

1048708 Its cells secrete ions such as potassium (K+) and acid (H+) into the tubular fluid

1048708 Reabsorption of water also occurs here under the influence of two hormones aldosterone and antidiuretic hormone

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Collecting Tubules and CollectingDucts

If an individual is well hydrated the collecting ducts simply transport the tubular fluid into the papillary duct and then into the minor calyx

1048708 However if an individual is dehydrated water conservation must occur and more-concentrated urine is produced

1048708 ADH may act on the collecting duct epithelium making it more able to absorb water from the tubular fluid

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Innervation of the Kidney

Each kidney is innervated by a mass of autonomic nervous system fibers collectively called the renal plexus

1048708 The renal plexus accompanies each renal artery and enters the kidney through the hilum into the renal sinus

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Urinary Tract

The ureters are long fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

1048708 Each tube averages 25 centimeters in length and is retroperitoneal

1048708 The ureters originate at the renal pelvis as it exits the hilum of the kidney and then extend inferiorly to enter the

posterolateral wall of the base of the urinary bladder 1048708 The wall of the ureter is composed of three concentric tunics 1048708 From innermost to outermost these tunics are the mucosa

muscularis and adventitia

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Urinary Tract ndash Urinary Bladder

The urinary bladder is an expandable muscular container that serves as a reservoir for urine It is positioned immediately superior and posterior to the pubic symphysis

1048708 In females the urinary bladder is in contact with the uterus posterosuperiorly and with the vagina posteroinferiorly

1048708 In males it is in contact with the rectum posterosuperiorly and is immediately superior to the prostate gland

1048708 The urinary bladder is a retroperitoneal organ When empty the urinary bladder exhibits an upside-down

pyramidal shape 1048708 Filling with urine distends it superiorly until it assumes an

oval shape

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Urinary Tract ndash Urinary Bladder

A posteroinferior triangular area of the urinary bladder wall called the trigone is formed by imaginary lines connecting the two posterior ureteral openings and the anterior urethral opening

1048708 The trigone remains immovable as the urinary bladder fills and evacuates

1048708 It functions as a funnel to direct urine into the urethra as the bladder wall contracts to evacuate the stored urine

1048708 The four tunics that form the wall of the bladder are the mucosa submucosa muscularis and adventitia

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Micturition (Urination)

The expulsion of urine from the bladder 1048708 Initiated by a complex sequence of events

called the micturition reflex 1048708 The bladder is supplied by both

parasympathetic and sympathetic nerve fibers of the autonomic nervous system

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Urethra

Fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts

urine to the exterior of the body The luminal lining of the urethra is a protective mucous

membrane that houses clusters of mucin-producing cells called urethral glands

Bundles of primarily smooth muscle fibers surround the mucosa and help propel urine to the outside of the body

1048708 Two urethral sphincters restrict the release of urine until thepressure within the urinary bladder is high enough and voluntary activities needed to release the urine are activated

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Urethra

The internal urethral sphincter is the involuntary superior sphincter surrounding the neck of the bladder where the urethra originates

ndash a circular thickening of the detrusor muscle and is controlled by the autonomic nervous system

1048708 The external urethral sphincter is inferior to the internal urethral sphincter and is formed by skeletal muscle fibers of the urogenital diaphragm

ndash a voluntary sphincter controlled by the somatic nervous system

ndash this is the muscle children learn to control when they become ldquotoilet-trainedrdquo

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Female Urethra

Has a single functionndash to transport urine from the urinary bladder to the

vestibule an external space immediately internal to the labia minora

1048708 3 to 5 centimeters long and opens to the outside of the body at the external urethral orifice located in the female perineum

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Male Urethra

Urinary and reproductive functions passageway for both urine and semen Approximately 18 to 20 centimeters long 1048708 Partitioned into three segments

ndash prostatic urethra is approximately 3 to 4 centimeters long and is the most dilatable portion of the urethra extends through the prostate gland immediately inferior to the male bladder where multiple small prostatic ducts enter it

ndash membranous urethra is the shortest and least dilatable portion extends from the inferior surface of the prostate gland through the urogenital diaphragm

ndash spongy urethra is the longest part (15 centimeters) encased within a cylinder of erectile tissue in the penis called the corpus spongiosum extends to the external urethral orifice

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost

Aging and the Urinary System

Changes in the size and functioning of the kidneys begin at 30 1048708 Gradual reduction in kidney size 1048708 Reduced blood flow to the kidneys 1048708 Decrease in the number of functional nephrons 1048708 Reabsorption and secretion are reduced 1048708 Diminished ability to filter and cleanse the blood 1048708 Less aldosterone or antidiuretic hormone 1048708 Ability to control blood volume and blood pressure is

reduced 1048708 Bladder decreases in size 1048708 More frequent urination 1048708 Control of the urethral sphinctersmdashand micturation may be

lost