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Chapter 18

Chapter 18. The Urinary System. Introduction. Maintains homeostasis Removes and restores solutes and fluids Organs Two kidneys: main filtering organs, produce urine Two ureters One bladder One urethra. Introduction (cont’d.). Functions of the Urinary System.

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Chapter 18

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  1. Chapter 18 The Urinary System

  2. Introduction • Maintains homeostasis • Removes and restores solutes and fluids • Organs • Two kidneys: main filtering organs, produce urine • Two ureters • One bladder • One urethra

  3. Introduction (cont’d.)

  4. Functions of the Urinary System

  5. Functions of the Urinary System (cont’d.) • Excretion: nitrogenous, drugs and toxins • Maintaining blood volume and concentration • Balance of water and dissolved salts • pH regulation • Balance of hydrogen ions

  6. Functions of the Urinary System (cont’d.) • Blood pressure maintenance • Renin • Erythrocyte concentration • Erythropoietin: stimulates red blood cell production • Vitamin D production • Calciferol

  7. The External Anatomy of the Kidneys

  8. The External Anatomy of the Kidneys (cont’d.) • Paired organs that are reddish in color • About the size of a closed fist • Located just above waist • Between parietal peritoneum and posterior wall of abdomen • Referred to as retroperitoneal

  9. The External Anatomy of the Kidneys (cont’d.) • Hilum: passage area for ureters, vessels, nerves • Surrounding layers • Renal capsule: innermost, barrier • Adipose capsule: middle, protection • Renal fascia: outer, anchors kidney

  10. The Internal Anatomy of the Kidneys

  11. The Internal Anatomy of the Kidneys (cont’d.)

  12. The Internal Anatomy of the Kidneys (cont’d.) • Medulla: inner area • Renal pyramids: tips point inward • Cortex: outer area • Cortical material between pyramids • Cortex and renal pyramids contain nephrons

  13. The Internal Anatomy of the Kidneys (cont’d.) • Nephrons: functional units of the kidney • Minor calyx • Funnel shaped, collects urine from pyramid ducts • Major calyces: formed from minor calyces • Join to form renal pelvis • Renal pelvis narrows to form ureter

  14. The Anatomy of the Nephrons

  15. The Anatomy of the Nephrons (cont’d.) • Nephron: microscopic renal tubule • Bowman’s glomerular capsule: double-walled globe • Podocytes: innermost layer • Parietal layer: outermost layer • Endothelial-capsular membrane: filter

  16. The Anatomy of the Nephrons (cont’d.) • Renal tubule • Proximal convoluted tubule • Descending limb, loop and ascending limb of Henle • Distal convoluted tubule • Collecting ducts

  17. Blood and Nerve Supply to the Nephrons

  18. Blood and Nerve Supply to the Nephrons (cont’d.)

  19. Blood and Nerve Supply to the Nephrons (cont’d.) • Renal arteries: transport 1200 mL of blood per minute • Interlobar arteries • Arcuate arteries • Interlobular arteries • Afferent arterioles divide into glomerular capillaries

  20. Blood and Nerve Supply to the Nephrons (cont’d.) • Efferent arterioles • Peritubular capillaries • Interlobular veins drain into arcuate vein • Interlobar veins • Renal veins

  21. Physiology of the Nephrons

  22. Physiology of the Nephrons (cont’d.) • Functions • Control blood concentration and volume • Regulate blood pH • Remove toxins from blood • Stimulate red blood cell production

  23. Physiology of the Nephrons (cont’d.) • Urine formation • Glomerular filtration • Tubular reabsorption • Tubular secretion • Urine: 95% water, urea, uric acid, electrolytes • 56 mL an hour is normal • 30 mL an hour indicates possible kidney failure

  24. The Ureters: Anatomy and Function

  25. The Ureters: Anatomy and Function (cont’d.) • Extensions of the renal pelvis • Connect to urinary bladder • Function: transport urine to urinary bladder • Urine movement • Peristalsis, gravity, hydrostatic pressure

  26. The Urinary Bladder and the Micturition Reflex

  27. The Urinary Bladder and the Micturition Reflex (cont’d.) • Urinary bladder held in position by peritoneum • Trigone: region between openings of ureters and urethra • Detrusor muscle: three-layered smooth muscle • Internal urinary sphincter: involuntary control

  28. The Urinary Bladder and the Micturition Reflex (cont’d.) • Micturition: expulsion of urine from bladder • External urinary sphincter: voluntary control • Bladder capacity • 700-800 mL • 200-400 mL: conscious of need to urinate • Stretch receptors initiate micturition reflex

  29. The Urinary Bladder and the Micturition Reflex (cont’d.) • During urination • Detrusor muscle contracts • Muscles of pelvic floor and abdominal wall contract • External urinary sphincter relaxes and urine moves from bladder to the outside

  30. The Urethra: Male and Female Positions

  31. The Urethra: Male and Female Positions (cont’d.) • Urethra: connects bladder to the outside • Females • Lies directly posterior to pubic symphysis • Located in wall of vagina • 3.8 cm long • Between clitoris and vaginal opening

  32. The Urethra: Male and Female Positions (cont’d.) • Males • 20 cm long • Passes through prostate gland and penis • Opens at tip of penis • Transports urine and semen

  33. Animation – Urine Formation • This animation presents an overview of how urine is formed • [Insert Urine Formation.swf]

  34. Summary • Discussed the functions of the urinary system • Described the internal and external anatomy of the kidney • Discussed the structure and function of the nephron • Discussed micturition and the role of the ureters and urinary bladder

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