1. Chapter Fifteen
The Urinary System

2. Urinary System Contribution to Homeostasis
Regulates body water levels
Excess water taken in is excreted
Output varies from 2-1/2 liter/day to 1 liter/hour
Regulates nitrogenous and other solute waste
Nitrogen from amino acids are made into urea in liver and transported to kidney as waste
Other solutes
Sodium, chloride, potassium, calcium, hydrogen ions, creatinine

3. Urinary System Kidney Cortex Renal artery Renal vein Nephrons Aorta
Inferior vena cava
Medulla
Renal pelvis
Medulla
Collecting duct
Ureter
Bladder
Ureter
Urethra
a) The components of the urinary system.
b) Internal structure of the kidney.
c) The cortex and medulla of the kidney are composed of numerous nephrons.

5. Organs of the Urinary System
Kidneys
Principle organ
Cortex - outer
Medulla - inner

6. Urinary System Kidney Cortex Renal artery Renal vein Nephrons Aorta
Inferior vena cava
Medulla
Renal pelvis
Medulla
Collecting duct
Ureter
Bladder
Ureter
Urethra
a) The components of the urinary system.
b) Internal structure of the kidney.
c) The cortex and medulla of the kidney are composed of numerous nephrons.

7. Organs of the Urinary System
Ureters
Transport urine to bladder
Urinary bladder
Stores urine (600–1000 ml)
Urethra
Carries urine from body
Two sphincters
Males about 20 cm, females about 4 cm

8. Organs of the Urinary System
Urinary bladder
Rectum
Internal urethral sphincter
Prostate gland
Uterus
Vagina
External urethral sphincter
Penis
Rectum
Urethra
Testis
a) The male
b) The female

9. Tubular and Vascular Nephron Components

10. Nephrons: Produce Urine
Tubules
Function
Filter fluid and reabsorb needed substances
Structures
Proximal tubule
Loop of Henle
Distal tubule
Collecting duct

11. Nephrons: Produce Urine
Blood vessels associated with tubules
Arterioles
Afferent
Efferent
Capillaries
Glomerular
Peritubular
Vasa recta

12. Formation of Urine

13. Formation of Urine: Glomerular Filtration
Filters fluid from capillaries into glomerular capsule
Rate of filtration
Resting rate under local chemical control
Stress causes sympathetic nervous system to reduce blood flow to kidneys

14. Formation of Urine: Tubular Reabsorption
Tubular reabsorption returns water and needed solutes to blood capillaries
Sodium moved by active transport from tubule cells to interstitial fluid and diffuses to capillaries
Chloride passively accompanies sodium (balanced charge)
Water reabsorbed with salts
Movement of sodium creates energy to transport glucose and amino acids into renal tubule then diffuses to the interstitial fluid

15. Tubular Secretion
Tubular secretion removes other substances from blood
Purpose
Regulation of chemical levels in body
Excretion of harmful chemicals
Substances secreted
Penicillin, cocaine, marijuana, pesticides, preservatives, hydrogen ions, ammonium, potassium

16. Concentration or Dilution of Urine: ADH (anti-diuretic hormone)
Formation of Dilute urine (see next slide for diagram)
Excreting excess water
Mechanism
Cycling of NaCl and urea create a concentration gradient in the medulla that allows water to diffuse from the renal tubules into the interstitial fluid and then into the blood capillaries

17. Formation of Dilute Urine

18. Concentration or Dilution of Urine: ADH
Formation of concentrated urine (see next slide)
Conserving water
Mechanism
Countercurrent exchange
Increased ADH causes increased permeability to the collecting tubules and increased conservation of water

19. Formation of Concentrated Urine

20. Urination Micturition reflex Internal urethral sphincter
Smooth muscle
External urethral sphincter
Skeletal muscle

21. Kidney’s Role in Homeostasis
Maintains water balance
Adjusts blood volume and blood pressure
Aldosterone, renin, ANH help maintain salt balance in order to control blood volume
Maintains acid–base balance and blood pH
Regulates red blood cell production via erythropoietin
Activates an inactive form of vitamin D

22. Kidney’s Role in Homeostasis

23. Kidney’s Role in Homeostasis