The Urinary System

1. The Urinary System

2. I. Introduction 1) The kidneys maintain the purity and constancy of our internal fluids. 2) Each day, they filter gallons of fluid, process the filtrate and remove wastes and excess ions in urine. 3) They also regulate blood’s volume and chemical makeup maintaining a balance between water and salts

3. 4) They produce a) Renin & Erythropoietin: b) Converts Vit.D to its active form 5) The urinary system also includes the ureters, bladder and urethra

4. Organs of the Urinary system • Kidneys • Ureters • Urinary bladder • Urethra Figure 15.1a

5. II. Kidneys 1) Location a) Bean like, dark red organs against the dorsal wall b) They are behind the T12 –L 3 vertebra c) The right kidney is slightly lower because of the liver 2) Description: a) About 12 CM long X 6 cm wide X 3 cm thick

6. b) Renal hilus: c) Adrenal glands sit on top of each kidney d) Renal capsule: 3) Parts: a) Cortex: lighter, outer part b) Medulla: darker, inner part

7. c) Medullary pyramids: triangular regions within the medulla, separated by renal columns d) Renal pelvis: funnel shaped end of the ureter e) Calyces: encloses the tip of the pyramids to collect urine

8. Regions of the Kidney Figure 15.2b

9. III. Nephrons 1) Nephron: the microscopic structural and functional unit of the kidney 2) Parts: Glomerulus, Bowman’s capsule & Tubules 3) Path of urine: glomerulus  Bowman’s capsule  proximal CT  loop of Henle  distal CT  collecting tubule  Collecting ducts  renal pelvis  ureter  urinary bladder  urethra

10. Figure 15.3c

11. 4) Urine formation: a) Filtration: b) Tubular reabsorption: passive and active process returning material to the blood from the filtrate c) Tubular secretion: Removing material from the blood into the filtrate 5) Urine characteristics: a) Freshly voided: clear and pale to deep yellow, slightly acidic b) Urochrome: pigment resulting from hemoglobin breakdown

12. Formation of Urine Figure 15.5

13. c) Bacteria cause urine to cloud and release ammonia d) Normal constituents: Na, K, Ca, urea, uric acid, creatine, ammonia, bicarbonate, sulfuric acid, phosphoric acid e) Abnormal materials can indicate a disorder (Table 15.1)

14. IV. Other structures 1) Ureter: 2) Urinary bladder has rugae 3) Bladder can hold up to 1000 ml

15. 3) Urethra: a) Internal urethral sphincter: Involuntary muscle closing the urethra b) External urethral sphincter: voluntary muscle controlling urination 4) Micturition: a) also called voiding: release of urine b) Bladder collects urine until it holds about 200 ml, it then passes through the internal sphincter and the urge to void occurs

16. c) This urge will stop until the volume reaches 400-500 ml d) Loss of control usually occurs at 700 ml

17. V. Fluid and electrolyte balance 1) Water makes up a varying % of body weight a) 50% young adult females b) 60% young adult males c) 75% babies d) 45% in old age 2) Water is located in the intracellular space, interstitial fluid, plasma (small amounts in other areas)

18. Distribution of Body Fluid Figure 15.8

19. 3) Water and electrolyte levels are closely associated 4) Slight changes in electrolyte balance causes water to move from one area to another 5) To maintain balance we must take in enough water to equal what is removed 6) Kidneys help regulate water loss by producing dilute or concentrated urine

20. 7) Kidneys also regulate electrolyte balance during urine production 8) Hormones: a) Osmoreceptors in the hypothalamus become more active when water levels fall b) ADH: hormone released to prevent excess water loss by causing duct cells to reabsorb more water

21. c) Aldosterone: Regulates sodium ions, effecting water balance 9) Blood pH a) Blood maintains a pH between 7.35 & 7.45 b) Metabolism releases H ions causing pH to change in blood

22. c) Buffers help maintain pH by reacting with these ions d) Major buffers: bicarbonate, phosphate and protein buffer e) The kidneys remove excess acidic compounds from the body

23. Maintaining Water and Electrolyte Balance Figure 15.10