2. Chapter 18
The Urinary System

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

4. Introduction (cont’d.)

5. Functions of the Urinary System

6. 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

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

8. The External Anatomy of the Kidneys

9. 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

10. 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

11. The Internal Anatomy of the Kidneys

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

13. 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

14. 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

15. The Anatomy of the Nephrons

16. 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

17. 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

18. Blood and Nerve Supply to the Nephrons

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

20. 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

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

22. Physiology of the Nephrons

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

24. 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

25. The Ureters: Anatomy and Function

26. 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

27. The Urinary Bladder and the Micturition Reflex

28. 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

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

30. 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

31. The Urethra: Male and Female Positions

32. 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

33. 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

34. Animation – Urine Formation
This animation presents an overview of how urine is formed
[Insert Urine Formation.swf]
Needs Animation introductory text and link

35. 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