Ureters Slender tubes attaching the

kidney to the bladder

• Continuous with the renal pelvis

• Enter the posterior aspect of the bladder

Runs behind the peritoneum

Peristalsis aids gravity in urine transport

Urinary Bladder Function

• Smooth, collapsible, muscular sac

• Temporarily stores urine

Trigone Structure

Bladder Wall

• Three layers of smooth muscle (detrusor muscle)

• Mucosa made of transitional epithelium

• Walls are thick and folded in an empty bladder

• Bladder can expand significantly without increasing internal pressure

• Internal and external sphincters

Figure 15.6

Urethra Thin-walled tube that carries urine from the bladder to

the outside of the body by peristalsis

Release of urine is controlled by two sphincters

• Internal urethral sphincter (involuntary)

• External urethral sphincter (voluntary)

Length and Location

• Females – 3–4 cm (1 inch), along wall of the vagina

• Males – 20 cm (8 inches) through the prostate and penis

Function

• Females – only carries urine

• Males – carries urine and is a passageway

Micturition (Voiding) Both sphincter muscles must open to allow

voiding

• The internal urethral sphincter is relaxed after stretching of the bladder

• Activation is from an impulse sent to the spinal cord and then back via the pelvic splanchnic nerves

• The external urethral sphincter must be voluntarily relaxed

Urinary System I: Kidneys and Urine Formation Functions of the Urinary System

Organs of the Urinary System

The Kidney

• Coverings and Regions

• Blood Flow

• Nephrons: Glomeruli and Renal Tubules

• Urine Formation

Urinalysis

Ureters, Bladder, and Urethra

Characteristics of Urine Used for Medical Diagnosis

Colored somewhat yellow due to the pigment urochrome (from the destruction of hemoglobin) and solutes; darker if patient dehydrated, lighter if over hydrated.

Sterile

Slightly aromatic

Normal pH of around 6

Specific gravity of 1.001 to 1.035; higher if concentrated, lower if dilute.

Checking for

• Glycosuria (excessive sugary food intake or diabetes)

• Proteinuria (intense exercise, pregnancy, hypertension)

• Pyuria (pus from urinary tract infections)

• Hemoglobinuria (from transfusion reactions or hemolytic anemia)

• Bilirubinuria (hepatitis)

• Pyelonephritis (high specific gravity)

Urinary System II: Fluid, Electrolyte, and Acid/Base Balance Distribution of Body Fluid

Maintaining Water Balance

Hormornal Regulation of Water and Salt

Acid-Base Balance

• Blood Buffers

• Regulation by Lung Respiration

• Regulation by Kidney on Bicarbonate

Developmental Aspects of the Urinary System

Most Body Fluid is Within Cells Intracellular fluid (inside

cells)

Extracellular fluid (outside cells)

• Interstitial fluid

• Blood plasma

Normal amount of water in the human body

• Young adult females – 50%

• Young adult males – 60%

• Babies – 75%

• Old age – 45%

•Low Na+ and Cl–

•Major cation: K+

•Major anion HPO42–

Maintaining Water Balance Water intake must equal water output

• Sources for water intake

o Ingested foods and fluids

o Water produced from metabolic processes

• Sources for water output

o Vaporization out of the lungs

o Lost in perspiration

o Leaves the body in the feces

o Urine production

Urine Output

• Dilute urine is produced if water intake is excessive

• Less urine (concentrated) is produced if large amounts of water are lost

• Proper concentrations of various electrolytes must be present

Maintaining Water and Electrolyte Balance

Maintaining Acid-Base Balance in Blood Blood pH must remain between 7.35 and 7.45 to maintain

homeostasis

• Alkalosis – pH above 7.45

• Acidosis – pH below 7.35

Most ions originate as byproducts of cellular metabolism

Acid-base control

• Blood buffers (immediate, first line regulator of pH)

• Respiration rate (reacts in 1-3 minutes)

• Renal/Kidney mechanisms exert strongest effect but slow (hours-days)

Chemical Buffer Systems of the Body

1. Bicarbonate buffer system

o Major buffer for the extracellular fluid, also intracellular fluid

o H2O + CO2 <--> H2CO3 <--> HCO3- + H+

2. Phosphate buffer system

o Effective buffer in urine and ICF, where phosphate concentrations are high

o (H3PO4 <--> H2PO4– + H+ <--> HPO4

2– + H+),

3. Protein buffer system

o Mostly active within cells, some effects in plasma

o Amino groups bind H+ (-NH2 + H+ <--> NH3+)

o Carboxyl groups remove OH- (-COOH + OH- <--> -COO- + H2O

Buffers react to prevent dramatic changes in hydrogen ion (H+) concentrations

• Bind to H+ when pH drops

• Release H+ (or bind OH-) when pH rises

The Bicarbonate Buffer System

Renal Mechanisms of Acid-Base Balance Excrete bicarbonate ions if needed

Conserve or generate new bicarbonate ions if needed

• Bicarbonate conservation or production causes rise in blood pH

• Bicarbonate excretion causes fall in blood pH

• H+ excretion in the urine

Urine pH varies from 4.5 to 8.0-+

2 2 2 3 3CO + H O H CO H + HCO

Acidosis and Alkalosis: Why It Matters Acidosis

• Blood pH below 7 depression of CNS coma death

• Enzymes denature

Alkalosis

• Blood pH above 7.8 excitation of nervous system muscle tetany, extreme nervousness, convulsions, respiratory arrest

• Enzymes denature

Metabolic Acidosis and Alkalosis Any pH imbalance not caused by abnormal blood CO2 levels;

indicated by abnormal HCO3– levels

Metabolic Acidosis

• Caused by ingestion of too much alcohol ( acetic acid), excessive loss of HCO3

– (e.g., persistent diarrhea)

• Causes by accumulation of lactic acid, shock, ketosis in diabetic crisis, starvation, and kidney failure

Metabolic Alkalosis (much less common than metabolic acidosis)

• Indicated by rising blood pH and HCO3–

• Caused by vomiting of the acid contents of the stomach or by intake of excess base (e.g., antacids)

Developmental Aspects of the Urinary System Fetal Development and Newborns

• Functional kidneys are developed by the third month

• Urinary system of a newborn

o Bladder is small

o Urine cannot be concentrated

• Control of the voluntary urethral sphincter does not start until age 18 months

• Urinary infections are the only common problems before old age

Effects of Aging on Urinary System

• There is a progressive decline in urinary function

• The bladder shrinks with aging

• Urinary retention is common in males

Congenital Abnormalities of the Urinary System

• Polycystic kidney

• Hypospadias

Hypospadias

Urinary System II: Fluid, Electrolyte, and Acid/Base Balance Distribution of Body Fluid

Maintaining Water Balance

Hormornal Regulation of Water and Salt

Acid-Base Balance

• Blood Buffers

• Regulation by Lung Respiration

• Regulation by Kidney on Bicarbonate

Developmental Aspects of the Urinary System