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 4.5-8.0) Specific gravity = 1.001-1.035 Chemical composition = 95% water,

5% solutes (urea, Na+, K+, PO4, SO4,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, 200-300 ml more will

accumulate before reflex returns Incontinence - inability to control

voiding Urinary retention - inability to void