Urinary system

Primary functions Maintenance of homeostasis Removal of substances from the blood Urea Creatinine Ammonia Products of drugs Regulation of: Blood volume Electrolytes Acid-base balance Blood pressure

Primary functions cont. Secretion of Renin Juxtaglomerular cells secrete renin, an enzyme, when BP decreases Renin activates the renin-angiotensin mechanism to increase BP Renin-angiotensin mechanism results in increased BP Vasoconstriction Stimulation of adrenal cortex to secrete aldosterone Secretion of erythropoietin Secreted during states of hypoxia Stimulates red bone marrow to produce RBC’s

Primary functions cont… The kidney and vitamin D Converts vitamin D to calciferol Calciferol increases small intestine’s ability to absorb calcium and phosphate

Main organs 2 kidneys Ureters Urinary bladder Urethra

kIdneys Cleanse the blood of waste Maintain blood pressure Maintain oxygen carrying ability of the blood Maintain the pH and electrolyte balance

Kidney - anatomy Left kidney more elevated Retroperitoneal – behind the peritoneum Located at the level of the T11, T12, and L1 vertebra Covered with fat to protect and hold in place Adrenal glands sit on top Hilum Place where renal artery/vein enter/exit Ureter exits Renal nerves enter/exit

3 major divisions of kidney Renal cortex Renal corpuscles Convoluted tubules Renal medulla Loops of henle Collecting tubules Renal pyramids Renal pelvis Calyces Collects urine draining from papillae

Nephron structure Most of the nephron located in cortex 1 million Responsible for all urine formation

Nephron structure Renal Corpuscle Filtration takes place here Bowman’s capsule glomerulus

Nephron structure cont… Proximal convoluted tubule Site of most reabsorbtion of nutrients Loop of henle Water and sodium are reabsorbed and urine is concentrated Distal convoluted tubule Anything not already reabsorbed will be excreted with urine

Special cells in the nephron JG cells – juxtaglomerular Cells located in the afferent ateriole Monitor blood pressure Release renin to stimulate aldosterone to increase BP Monitor oxygen in the blood Release erythropoietin to increase RBC’s

Kidney blood supply Renal artery Afferent arterioles Glomerulus Efferent arterioles Peritublar capillaries Veins Renal vein

Ureter Carry urine to bladder Peristalsis Connect to underside of bladder (trigone) Right 10 inches left 12 inches Trigone Formed by the union of the 2 ureters and urethra Most commonly infected area

bladder Muscular sac that stores urine for micturition Holds 500 mL Located inferior to uterus in females Located superior to prostate in males Lined with transitional epithelium to allow stretch Detrusor muscle Internal urethral sphincter = involuntary

urethra Carries urine out of body 1-1.5 inches in females 7-8 in males Higher incidence of UTI’s 7-8 in males External urethral sphincter = voluntary

Major processes of urine formation Filtration Reabsorbtion Secretion