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URINARY SYSTEM

URINARY SYSTEM. URINARY SYSTEM: OVERVIEW. Cellular wastes are toxic if not removed Waste removal (from cells) is performed by blood and lymph Elimination of wastes Urinary system: H 2 O, electrolytes, nitrogenous wastes, drugs Respiratory system: CO 2 and H 2 O

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URINARY SYSTEM

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  1. URINARY SYSTEM

  2. URINARY SYSTEM: OVERVIEW • Cellular wastes are toxic if not removed • Waste removal (from cells) is performed by blood and lymph • Elimination of wastes • Urinary system: H2O, electrolytes, nitrogenous wastes, drugs • Respiratory system: CO2 and H2O • Integumentary system: H2O, electrolytes

  3. URINARY SYSTEM: FUNCTIONS • Waste removal • Maintenance of water/electrolyte balance • Regulation of body fluid volume and blood pressure • Control of RBC production

  4. ANATOMY: MACROSCOPIC • Kidneys (2): Filter, reabsorb, secrete • Ureters (2): Convey urine to bladder • Urinary bladder (1): Collects and stores urine • Urethra (1): Conveys urine out of body

  5. Red-brown, bean shaped Enclosed in fibrous capsule Retroperitoneal Surrounded by adipose tissue ANATOMY: KIDNEY Continued ...

  6. Hilum or Hilus (Indentation; Passage of Vessels, Nerves, etc.) Renal Cortex (Outer) Renal medulla (Inner) Renal Pyramids (Conical Masses) Renal Columns (Extensions of Cortical Tissue between Pyramids) ANATOMY: KIDNEY continued

  7. Functional Units: Nephrons Renal Papillae (Tip of Pyramid) Minor Calyces (“Cup” receives Urine from Collecting Duct/Renal Papillae) Major Calyces (Receives from Minor C.) Renal Pelvis (Expanded Proximal End Ureter) ANATOMY: KIDNEY continued

  8. Hollow tubes ~25cm (10”) in length Extend from kidneys to urinary bladder Located retroperitoneally Muscular walls undergo peristalsis Flaps of Mucosa at openings into bladder; prevent backflow ANATOMY: URETERS

  9. Hollow, muscular, distensible sac Located in true pelvis, subperitoneally Attached to pelvic floor at trigone 3 layers: Inner muscosa (Transitional E.T. allows filling w/o pressure increase) Middle detrusor muscle (smooth) Outer Adventitia Serosa (visceral peritoneum) covers only superior surface ANATOMY: URINARY BLADDER

  10. ANATOMY: URETHRA • Males • Combined Urogenital System • Long urethra (~18 cm) in three subdivisions • Prostatic urethra • Membranous urethra • Penile or spongy urethra • Females • Separate reproductive and urinary systems • Short urethra (~4 cm)

  11. Nephron: Functional unit of kidney Approximately 1 million/kidney Found Mostly in Renal Cortex Consists of : Renal Corpuscle (Glomerulus + Bowman’s Capsule) Renal Tubules (Proximal & Distal Convoluted Tubules + Loop of Henle) Collecting Duct – Receives from Multiple Nephrons ANATOMY: MICROSCOPIC

  12. URINE FORMATION • Three Processes: • Filtration • Reabsorption • Secretion • Countercurrent Exchange • fluids moving in opposite directions

  13. Depends on blood pressure (“Pressure Filtration”) Afferent Arteriole carries blood to Glomerulus Small molecules and water move through Walls of Glomerulus into Bowman’s Capsule Fluid is filtrate Includes most substances found in urine Filtrate is similar to plasma (Water, Glucose, Ions, Amino Acids, small Nitrogenous Wastes) GLOMERULAR FILTRATION

  14. Selective Movement of molecules from renal tubules back into blood PCT Reabsorbs Water, Glucose, Amino Acids, Ions (up to 80% of filtrate) Loop of Henle (& Collecting Duct) Concentrates Urine/Reabsorbs Water & Ions Microvilli for High SA & Absorption TUBULAR REABSORPTION

  15. Primarily in DCT (& Collecting Duct) Additional Molecules move: Blood  Renal Tubules Active Transport or Osmosis Water Ions (H+, K+, Na+,Cl-) Some drugs, e.g., penicillin Creatinine Nitrogenous wastes TUBULAR SECRETION

  16. URINE PATHWAY • Nephron  Collecting Duct (Out Renal Papilla of Renal Pyramid)  Minor Calyx  Major Calyx  Renal Pelvis  Ureter  Urinary Bladder  Urethra  Outside Body

  17. 95% water pH 6.0 (avg.) Urea: From proteins Uric acid: From nucleic acids Creatinine: From creatine phosphate Amino acids: A trace Electrolytes: Vary with diet COMPOSITION OF URINE: NORMAL

  18. REGULATION OF FLUID VOLUME • Antidiuretic Hormone (ADH) • Released when blood volume drops • Increases permeability of collecting duct to water • Results in: • Increase in Water Reabsorption (decreases water loss) • Increase in Blood Volume

  19. REGULATION OF FLUID VOLUME continued • Relationship of blood pressure to urine formation • Blood pressure is required for glomerular filtration • If blood pressure falls below a certain point, filtration stops • Results in build-up of nitrogenous wastes

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