The Urinary SystemThe Urinary System

KidneyKidney

Small, dark red organs with a kidney-bean shape lie Small, dark red organs with a kidney-bean shape lie Retroperitonealy in superior lumbar region. Retroperitonealy in superior lumbar region. against the dorsal body wall.against the dorsal body wall.

The kidneys extend from the T12 to the L3 vertebra.The kidneys extend from the T12 to the L3 vertebra.

The right kidney is positioned slightly lower than the The right kidney is positioned slightly lower than the left.left.

Adult kidney 12 cm (5 inches) longAdult kidney 12 cm (5 inches) long , 6 cm(2.5 , 6 cm(2.5 inches) wide, and 3 cm (1 inches) thick.inches) wide, and 3 cm (1 inches) thick.

It is convex laterally and has a medial indentation It is convex laterally and has a medial indentation called called the hilusthe hilus..

Adrenal gland (part of endocrine system) is on the Adrenal gland (part of endocrine system) is on the tope of each kidney.tope of each kidney.

Renal capsule (fibrous, transparent) encloses each Renal capsule (fibrous, transparent) encloses each kidney (glistening appearance).kidney (glistening appearance).

Adipose capsule (fatty mass) surrounds each kidney Adipose capsule (fatty mass) surrounds each kidney and holding it against trunk muscles.and holding it against trunk muscles.

Renal cortex (outer region, light in color).Renal cortex (outer region, light in color).

Renal medulla (darker reddish-brown area).Renal medulla (darker reddish-brown area). medullary pyramids (basically triangular regions medullary pyramids (basically triangular regions

with a striped appearance).with a striped appearance). the pyramids are separated by extensions of the pyramids are separated by extensions of

cortex-like tissue, the renal columns.cortex-like tissue, the renal columns.

Renal pelvis is a flat, basin like cavity medial to the Renal pelvis is a flat, basin like cavity medial to the hilus.hilus.

Calyces are extension of the pelvis, form cup-Calyces are extension of the pelvis, form cup-shaped areas that enclose the tips of the shaped areas that enclose the tips of the pyramids pyramids

Blood SupplyBlood Supply

Kidneys have a very rich blood supply.Kidneys have a very rich blood supply.

Each minute, one-quarter of the total blood supply Each minute, one-quarter of the total blood supply of the body passes through the kidneys.of the body passes through the kidneys.

Renal artery-Segmental-lobar- interlobar - arcuate - Renal artery-Segmental-lobar- interlobar - arcuate - interlobular arteries.interlobular arteries.

Venous blood draining from the kidney flows Venous blood draining from the kidney flows through veins that trace the pathway of the through veins that trace the pathway of the arterial supply but in a reverse direction. arterial supply but in a reverse direction.

Nephron Are structural and functional units of the

kidneys.

Glomerulus & Renal tubules.

Glomular or Bowman’s capsule, it is a closed end of the renal tubule is enlarged and cup-shaped and surrounds the Glomerulus.

The rest of the tubule is about 3 cm (1.25 inches).

Proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT).

Cells of PCT are covered with dense microvilli, which increases their surface area.

Cortical nephrons.Juxtamedullary nephrons.Collecting duct , it receives urine from many

nephrons running through the medullary pyramids givining them their stripped appearance

Two capillary sets: Glomerulus - peritubular capillary bed.

Glomerulus:

Afferent arteriole (feeder vessel)- Efferent arteriole .

Specialized for filtration

high-pressure

Peritubular capillary bed.

arises from efferent arterioles

Specialized for absorption

low-pressure

drain in to interlobular veins.

Ureters,UrinaryUreters,Urinary Bladder, and Bladder, and UrethraUrethra

UretersUretersSlender tubes- 25 to 30 cm (10-12 inches) long, and Slender tubes- 25 to 30 cm (10-12 inches) long, and

6 mm (1/4 inches) in diameter.6 mm (1/4 inches) in diameter.

Each ureter runs behind the peritoneum from the Each ureter runs behind the peritoneum from the hilus of the kidney to the posterior aspect of the hilus of the kidney to the posterior aspect of the bladder, which enters at a slight angles .bladder, which enters at a slight angles .

The ureters are passgeways that carry urine from The ureters are passgeways that carry urine from kidneys to the bladder.kidneys to the bladder.

Gravity, and peristalsis movement of the ureter are Gravity, and peristalsis movement of the ureter are helping urine drain to the bladder .helping urine drain to the bladder .

Small valve like folds of bladder mucosa is Small valve like folds of bladder mucosa is preventing urine from flowing back into ureter. preventing urine from flowing back into ureter.

Urinary BladderUrinary Bladder

A smooth, collapsible, muscular sac that stores urine A smooth, collapsible, muscular sac that stores urine temporarily temporarily . .

It is located retroperitoneally in the pelvisIt is located retroperitoneally in the pelvis..

Two ureter opening and the single opening of the Two ureter opening and the single opening of the urethra urethra..

Trigone is the smooth triangular region of the Trigone is the smooth triangular region of the bladder base outlined by these three bladder base outlined by these three

openingsopenings . .

The bladder wall contains three layers of smooth The bladder wall contains three layers of smooth muscle (detrusor muscle), and it’s mucosa muscle (detrusor muscle), and it’s mucosa

(transitional epithelium)(transitional epithelium) . .

It is collapsed, 5 to 7.5 cm (2 to 3 inches) long, and It is collapsed, 5 to 7.5 cm (2 to 3 inches) long, and it’s wall are thick and thrown into foldsit’s wall are thick and thrown into folds..

A moderately full bladder is about 12.5 cm (5 A moderately full bladder is about 12.5 cm (5 inches) long and holds 500 mlinches) long and holds 500 ml..

Distended bladder becomes firm and pear-shaped Distended bladder becomes firm and pear-shaped may be felt above the pubic symphysismay be felt above the pubic symphysis..

UrethraUrethra

The urethra is a thin-walled tube that carries urine The urethra is a thin-walled tube that carries urine by peristalsis from the bladder to the out side of by peristalsis from the bladder to the out side of the body.the body.

Internal urethral sphincter (a thickening of the Internal urethral sphincter (a thickening of the smooth muscle,an involuntary sphincter that smooth muscle,an involuntary sphincter that keeps the urethra closed.keeps the urethra closed.

External urethral sphincter is fashioned by skeletal External urethral sphincter is fashioned by skeletal muscle as the urethra passes through pelvic floor.muscle as the urethra passes through pelvic floor.

In females, it is 3 to 4 cm (1 1/2 inches) long.In females, it is 3 to 4 cm (1 1/2 inches) long.Lies anterior to vaginal opening.Lies anterior to vaginal opening.It’s function is to conduct urineIt’s function is to conduct urine

In male, it is 20 cm (8 inches) longIn male, it is 20 cm (8 inches) long Prostatic Prostatic Membranous Membranous Spongy, penile Spongy, penileIt’s function is to conduct urine, also it provides the It’s function is to conduct urine, also it provides the passage-ways through which the sperm is ejected passage-ways through which the sperm is ejected from the body.from the body.