Urinary/Excretory System Produces urine for elimination Essential for homeostasis normal blood composition acid base (pH) balance *Uremia  poisoning from wastes  build up  toxic 2 Kidneys: clear blood of waste products from cell metab. 2 ureters: extend from kidneys & drain urine into to bladder 1 bladder: stores urine 1 urethra: extends from bladder & drains urine to void Urinary Meatus: opening at end of urethra

Kidney Location: Above waist, towards back, under muscles Behind Parietal Peritoneum (lines abdomen) Encased in fat cushion (protects, anchors) Renal Ptosis: kidney drops  tubes kink  obstructs urine drainage Floating Kidneys: Obese w/ rapid wt loss lose xs kidneys drift

Internal Kidney Structure Cortex: outer Medulla: Inner Pyramids: ∆ shape division of medulla Papilla: ∆ Narrow innermost end of pyramid Pelvis: Expansion of upper end of ureter Calyx: Division of renal pelvis w/ papilla of pyramid

Narrow part of pyramid Renal pelvis w/ pyramid Inner layer Outer layer Triangle shape in medulla Drains urine from calyx Expansion of upper end of ureter Clean deO 2 Dirty & O 2

Microscopic Structure Each kidney > 1 million Nephrons Basic unit of S&F of kidney

Nephron: 2 main parts * Renal Corpuscle: Bowman’s Capsule: cap of glomerulus Glomerulus: Capillary network in BC Afferent arteriole (lg)  in Efferent arteriole (sm)  out creates ↑ pressure for filtration of wastes * Renal Tubule: Proximal Convoluted Tubule (PCT) (cortex) 1 st segment closest to Bowman’s Capsule Loop of Henle: extension of PCT (medulla) Distal Convoluted Tubule (DCT) (cortex) Extensions of ascending Loop of Henle Collecting Tubule: drains several DCT’s cortex  medulla

CORTEXCORTEX MEDULAMEDULA

Urine from collecting tubules drain into collecting duct  papilla  calyx  renal pelvis  ureter  bladder  urethra  urinary meatus

3 Steps in Urine Formation in Nephrons Filtration: continuous in renal corpusle high glomerular pressure from A/E arteriole pushes H 2 O & dissolved substances OUT of glomerulus INTO BC Ex. clean out desk  remove most everything but most return thru “resorption” If glomerular BP drops too low, (Ex. hemorrhage) filtration stops  kidney failure  dialysis Glomerular Filtration 125ml/min = 7500ml/hr = 180,000ml/day qts!!! But…most returns to blood thru peritubular capillary resorption!

Resorption: Mvmt of substances out of renal tubules into peritubular capillaries Substances resorbed: H 2 O, glucose, nutrients, Na, Ions (based on intake) Begins in PT, Loop of Henle, DT, CT 99% of H 2 O filtrate resorbed thru osmosis & glucose absorbed into peritubular capillaries thru AT in PT K, H 2 O resorbed in DT Diabetes Mellitus [blood glucose] ↑ so tubular filtrate contains more glucose than can be resorbed  Glucose in urine  glycosuria

Secretion: Opposite of resorption Substances move into urine in DT & CT from tubules Substances secreted: H+, K+, certain drugs (AT) NH 3 (diffusion) Role in maintaining acid/base (pH) balance & homeostasis

Control Of Urine Volume: Determined by amount of H 2 O & dissolved substances resorbed in PCT’s & DCT’s ADH (Anti-Diuretic Hormone): “H 2 O retaining Hormone” Made in hypothalamus Stored in Posterior Pituitary Gland ↓’s amount of urine by making Distal/Collecting tubules more permeable to H2O  ↑ resorption, results in ↓ urine

More ADH = ↓ urine b/c tubules more permeable to H 2 O Less ADH = ↑ urine b/c tubules less permeable to H 2 O Caffeine & Alcohol: ↓ ADH  ↑ urine (  dehydration) Nicotene: ↑ ADH  ↓ urine

Aldosterone Hormone: “Salt & H 2 O retaining hormone” Secreted by Adrenal Cortex Stimulates tubules to resorb H 2 O & salt faster Abnormal Urine Volume Excretion * Anuria: no urine * Oliguria: scant urine * Polyuria: large amts of urine Chilled  vasoconstriction  ↑ blood flow to organs so kidneys produce ↑ urine Outer: adrenal cortex Inner: adrenal medulla Fx in tubule resorption

Ureters: Drain urine out of collecting tubules  into Renal Pelvis  urinary bladder Mucous Membranes line ureters & renal pelvis Contraction of muscular coat  peristaltic movement of urine -> ureters  bladder

Urinary Bladder: Empty, lies in pelvis Full, projects up into lower abdominal cavity Elastic fibers & Involuntary Muscle fx in expansion Full: inner smooth Empty: Rugae folds (like stomach) Trigone: Extends into urethra * males

Renal Colic: Pain from Kidney Stones (Renal Calculi) Build up of Ca salts, uric acid, etc. Avoid by ↑ H 2 O intake Removal o kidney Stones: Small, may pass Large can obstruct urine flow or cause infection Treat: Lithotripsy shock waves pulverize stones in kidney, bladder, ureters, gall bladder too)  pass (Less invasive, faster recovery) Surgery: Invasive, more complications, ? Infection & $$$$!

Urethra: Lower most part of urinary tract Urine passes from bladder ↓urethra & out external opening (Urinary Meatus) ***Same mucous membrane that lines renal pelvis, ureters, blaader, extends into urethra (so infections can spread up easily. 8” in males 1.5” in females

Urinary Catheteritization: Insertion of catheter thru urethra into bladder  withdraw urine (For sterile sample, surgery, urinary retention) Requires asceptic technique to avoid infection, cystitis (inflammation of bladder / infection) UTI’s common nosocomial infection 

Micturition: Urination / Voiding / Emptying Bladder < 2 – 3yrs Reflex Action >2 – 3yrs Voluntary Action Internal Urethral bladder exit (Involuntary smooth muscle) External Urethral Sphincter (compressor urethrae) below bladder neck (Voluntary striated muscle) Both contracted seal off bladder, urine accumulates & bladder stretches  nerve impulses  emptying reflex  sphincters relax & contraction of bladder wall  urine  urethra  void

Conditions Urinary Retention: Kidneys produce urine but not voided Urinary Suppression: Kidneys don’t produce urine but bladder is able to empty Incontinence: Void involuntarily  Elderly, stroke, spinal cord injury lose muscle control  affects emptying reflex Cystitis: Bladder doesn’t empty completely Residual urine  chronic bladder infections Polyuria: ↑ urine output (hmm. ↓ levels of ADH, tubules less permeable don’t resorb as much H 2 O so it stays in urine))