URINARY SYSTEM Urology is the branch of medicine that deals with the urinary system and the male reproductive tract

Function Regulates volume, composition, and pH of body fluids Excretes metabolic wastes Regulates blood pressure, RBC production, activates calcitriol (vitamin D), and perform gluconeogenesis

Major structures Located retroperitoneally on each side of the vertebral column between T12-L3 Left kidney lower than right one Connective tissue layers: renal capsule, adipose capsule and renal fascia Ureters Bladder Urethra

Internal Anatomy Cortex Medulla Renal pyramids Renal columns Renal pelvis Calyces

Blood Supply Renal artery Segmental artery Interlobar artery Arccuate artery Interlobular arteries Afferent artery Glomerular capillaries Efferent arteries Peritubular/vasa recta Interlobular veins Arcuate veins Interlobar veins Segmental veins Renal vein

NEPHRON FUNCTIONAL UNIT OF THE KIDNEY

Nephron Renal corpuscle glomerulus Bowman’s capsule Renal tubule proximal convoluted tubule Loop of Henle distal convoluted tubule

Types of Nephrons Cortical nephron - contained almost entirely in the cortex Juxtamedullary nephron - go deep into the renal medulla; able to produce more concentrated urine

Glomerulus - Bowman’s capsule Glomerulus = network of capillaries arising from an afferent arteriole that empties into an efferent arteriole Bowman’s capsule is a double layer structure that receives the filtrate Consists of parietal and visceral layer

Endothelial - Capsular Membrane Glomerular endothelium - fenestrated Podocytes “foot cells” - intertwining processes cling to basement membrane of glomerulus

Renal Physiology

Filtration Glomerular filtration forces plasma and wastes products out of capillaries and into the Bowman’s capsule Net filtration pressure is primarily controlled by glomerular blood hydrostatic pressure Glomerular filtration rate is the amount of filtrate formed in both kidneys per minute 125 ml/min (180 L/day!!!)

Reabsorption Tubular reabsorption is the movement of water and other substances back into the blood such as glucose, amino acids, sodium, potassium, and other ions 99% of filtrate reabsorbed Occurs mainly in proximal tubule Both active and passive transport used Transport maximum

Secretion Occurs mainly in the DCT Acid-base balance and water adjustment Tubular secretion involves the movement of substances out of the blood into the tubules K + ions, urea, uric acid, drugs

Composition of Urine Color = clear to yellow; varies on concentration and diet Odor = develops ammonia odor pH = 6.0 (varies ) Specific gravity = Chemical composition = 95% water, 5% solutes (urea, Na +, K +, PO 4, SO 4,creatinine, uric acid)

Diuretics Enhance urinary output Common diuretics include: Caffeine, Alchol Usually inhibit sodium ion reabsorption

Urine Elimination Ureters Bladder Transitional epithelium Trigone Detrusor muscle Can hold 500-1,000 ml Urethra internal & external sphincters

Micturition = Urination = Voiding 200 ml = urge to void Voiding reflex relaxes internal sphincter If suppressed, ml more will accumulate before reflex returns Incontinence - inability to control voiding Urinary retention - inability to void