Urinary system

Kidneys Lie in superior lumbar region Extend from T12-L3 lumbar vertebra Retro-peritoneal organs Level ofT12-L3vertebra RT kidney is slightly lower than the left by half inch.

Kidney is 12 long x6 widex3 cm thick. Convex laterally, hilum medially which receive renal vein, artery, and ureter comes out Receive 25% of cardiac output Suprarenal gland lies above each kidney Kidney is surrounded by thin capsule Adipose capsule, facial capsule

The outer region is renal cortex Deep region is renal medulla, which has triangular areas called the pyramids, which are separated by renal columns Renal pelvis leads to the ureter, extension of the pelvis in to the kidney is the calyces, and form cup shaped areas

THE NEPHRON The nephron is the structural and functional unit of the kidney. Each kidney contains approximately 1 million nephrons. It is in the nephrons, with their associated blood vessels, that urine is formed. Each nephron has two major portions: a renal corpuscle and a renal tubule.

Cont. Renal Corpuscle A renal corpuscle consists of a glomerulus surrounded by a Bowman’s capsule. The glomerulus is a capillary network that arises from an afferent arteriole and empties into an efferent arteriole. The diameter of the efferent arteriole is smaller than that of the afferent arteriole, which helps maintain a fairly high blood pressure in the glomerulus.

Cont. Bowman’s capsule : (or glomerular capsule) is the expanded end of a renal tubule; it encloses the glomerulus. The inner layer of Bowman’s capsule is made of podocytes; the name means “foot cells,” and the “feet” of the podocytes are on the surface of the glomerular capillaries. The outer layer of Bowman’s capsule has no pores and is not permeable. The space between the inner and outer layers of Bowman’s capsule contains renal filtrate, the fluid that is formed from the blood in the glomerulus and will eventually become urine.

Cont. Renal Tubule The renal tubule continues from Bowman’s capsule and consists of the following parts: proximal convoluted tubule (in the renal cortex), loop of Henle (or loop of the nephron, in the renal medulla), and distal convoluted tubule (in the renal cortex). The distal convoluted tubules from several nephrons empty into a collecting tubule. Several collecting tubules then unite to form a papillary duct that empties urine into a calyx of the renal pelvis.

Ureters, urinary bladder, and urethra Ureters are 25 cm long,6mm in diameter Run behind peritoneum Start from hilum of the kidney to the posterior aspect of the bladder Smooth muscle in wall of Ureters contract to help urine movements to UB Urine is prevented from flow back to ureter by valve like folds of UB mucosa Enter bladder at an angle, superior part is continuous with pelvis of kidney

Urinary bladder Smooth collapsible muscular sac Located retroperitoneal, in pelvis just posterior to symphysis pubis Have three openings for Ureters and urethra Smooth triangular region is the trigone, infection persist in this area Prostate gland surround neck of UB in males Bladder wall contain three layers of smooth muscles called detrusor muscle Bladder when empty is 6 cm long,wall is thick and thrown into folds,12 cm when contain 500 ml of urine Urinary bladder is pelvic organ, felt in abdomen when only full

Urethra Extend from base of the bladder to tip of penis Have three parts, prostatic surrounded by the prostate gland Membranous urethra and penile urethra Have two sphincters, internal involuntary, external voluntary sphincter. Male urethra is 20 cm long, female urethra is only 4 cm long

Prostate gland Size of chestnut Surrounds prostatic urethra, below the urinary bladder Have many ducts open directly into prostatic urethra. Prostate lie anterior to rectum so can be felt by per rectum examination. Seminal vesicle located at base of bladder Produce 60% of seminal fluid volume Secretion is yellow rich in sugar vit c,prostaglandins Duct join the duct of vas deferens to form ejaculatory duct

TRANSITIONAL EPITHELIUM IN RELAXED STATE Is 4-5 cell layer thick Basal layer is cuboidal Intermediate layer is polyhedral surface layer is cuboidal with binucleate cells IN STRETCHED STATE Is 2-3 cell thick Surface layer is squamous Example : urinary tract