DEPARTEMEN ANATOMIFK-USUMEDAN

Tractus urinarius

• The urinary system of the human body consists of two kidneys, two ureters, the bladder and a single urethra.

• The kidneys are located on the posterior wall of the abdomen at waist level. Each kidney is roughly 10 cm long and 5 cm wide, and is encased in a fibrous outer capsule called the renal capsule.

• The main function of the kidneys is to control blood volume and composition. They do this by filtering the blood to remove waste products, salts and water. These are secreted in the form of urine.

• The kidneys are located in the posterior part of the abdomen.

• There is one on each side of the spine ,the right kidney sits just below the liver, the left below the diaphragma and adjacent to the spleen.

• Above each kidney is an adrenal gland (also called the suprarenal gland). The asymmetry within the abdominal cavity caused by the liver results in the right kidney being slightly lower than the left one while the left kidney is located slightly more medial.

• The kidneys are retroperitoneal and • They are approximately at the vertebral level T12 to L3.• The upper parts of the kidneys are partially protected

by the eleventh and twelfth ribs.• Congenital absence of one or both kidneys, known as

unilateral or bilateral renal agenesis, can occur

UreterThe ureters deliver urine to the bladder from the kidney

to bladder.The ureters are retroperitoneal, which means that

they are located in the retroperitoneal space .In adults the ureters are approx 12 inches (30 cm) long

and have a muscular coat that tightens and relaxes to move urine away from the kidney. This muscular action is controlled by the autonomic nervous system (ANS) and operates in a similar way to that of peristalsis in the digestive system.

The ureters pass through the posterior surface of the bladder at the Ureter Orifices.

Urine drains through the ureters directly into the bladder as there are no sphincter muscles or valves at the ureter orifices

Bladder• The bladder is located on the floor of the

pelvic cavity. (Other organs, glands and tissues located in the pelvic cavity include the rectum, gender-specific reproductive organs, parts of the small intestine, blood vessels, lymphatic vessels, and nerves).

• The bladder is located anterior to (i.e. in front of) the rectum in males.

• In females it is also in front of the uterus and upper vagina so its location is described simply as "anterior to the uterus and upper vagina".

The urinary bladder is a musculomembranous sac whose shape is affected by factors including the person's age and sex - as well as the volume of urine it contains at the time.

The "superior" or "abdominal" surfaces, and the "lateral" surfaces of the bladder are covered by peritoneum.

Bladder in pelvic cavity

Structure of Bladder

The bladder itself ("musculomembranous sac") consists of 4 layers:• Serous

The outer "serous" layer is a partial layer derived from the peritoneum.

• MuscularThe detrusor muscle is the muscle of the urinary bladder wall. It consists of three layers of smooth (involuntary) muscle fibres. The external layer is longitudinal, the middle layer is circular configuration, and the internal layer is longitudinal .

• Sub-mucousThis is a thin layer of areolar tissue .

• MucousThe innermost layer,which contains transitional epithelium tissue that can stretch. The ability of this tissue to stretch is important because it contains variable volumes of liquid - as the bladder is filled and emptied several times per day. Because it is only loosely attached to the (strong and substantial) muscular layer, the mucosa falls into many folds known as rugae when the bladder is empty or is only filled to a small extent.

Female urethra

At only about 1.5 inches (35 mm) long, the female adult urethra is shorter than the adult male urethra (approx. or 8 inches, or 200mm).

The female urethra is located immediately behind the pubic symphysis and is embedded into the front wall of the vagina.

The urethra itself is a narrow membranous canal that consists of three layers:Muscular layer - continuous with the muscular layer

of the bladder, this extends the full length of the urethra.

Thin layer of spongy erectile tissue - including plexus of veins and bundles of smooth muscle fibres. Located immediately below the mucous layer.

Mucous layer - internally continuous with the bladder and lined with laminated epithelium that is transitional near to the bladder.

After passing through the urogenital diaphragm ,the female urethra ends at the external orifice of urethra - which is the point at which the urine leaves the body. This is located between the clitoris and the vaginal opening.

The passage of urine along the urethra through the urogenital diaphragm is controlled by the external urethral sphincter, which is a circular muscle under voluntary control (that is, it is innervated by the somatic nervous system, SNS

Male urethra

At about 8-9 inches (200 mm) long, the adult male urethra is longer than the adult female urethra (of approx. 1.5 inches 35 mm).

It has three portions (the prostatic urethra, the membranous urethra, and the spongy urethra ) and extends from the neck of the bladder to the meatus urinarius at the end of the male penis/urethra.

The three regions/sections of the male urethra are:• Prostatic Urethra

The prostatic urethra begins at the neck of the bladder and includes all of the section that passes through the prostrate gland. It is the widest and most dilatable part of the male urethral canal.

• Membranous UrethraThe membranous urethra is the shortest and narrowest part of the male urethra. This section measures approx. 0.5 - 0.75 inches (12 - 19 mm) in length and is the section of the urethra that passes through the male urogenital diaphragm. The external urethral sphincter (muscle) is located in the urogenital diaphragm (as for the female urethra). The passage of urine along the urethra through the urogenital diaphragm is controlled by the external urethral sphincter, which is a circular muscle under voluntary control (that is, it is innervated by the somatic nervous system, SNS).

Spongy UrethraThe spongy urethra is the longest of the

three sections. It is approx. 6 inches (150 mm) in lengthIt is contained in the corpus spongiosum that

extends from the end of the membranous portion, passes through the penis, and terminates at the external orifice of the urethra - which is the point at which the urine leaves the body.