1. Urinary System

2. Functions
Maintains normal concentrations of water and electrolytes in body fluids
Regulates pH
Regulates volume of body fluids
Helps control RBC production
Helps control blood pressure

3. Organs of the Urinary System
Kidneys (paired bean shaped organs)
Filter blood and form urine
Ureters (paired tubes)
Transport urine from kidneys
Urinary bladder (single sac)
Stores urine
Urethra (single tube)
Transports urine outside
body

4. An introduction to the Urinary System

6. Internal Structure of the Kidney
Renal cortex – forms shell around the medulla. Forms renal columns (between renal pyramids)
Renal medulla
Made of renal pyramids
Renal pelvis
Continuous with ureter
Calyces (Major & minor)
Extensions into the renal pyramids
Function – collect urine

7. The Structure of the Kidney

8. Nephron Each kidney has about 1 million nephrons
Made of a renal tubule &
A renal corpuscle
Corpuscle =
glomerulus(capillaries)
Glomerular capsule (surrounds glomerulus)
Glomerulus filters plasma to form urine

9. A Representative Nephron

10. Urine Composition 95% water Urea (amino acids)
Uric acid (nulceic acids)
Trace amounts of amino acids
electrolytes

11. Urine Elimination Nephrons Collecting ducts Calyces (minor then major)
Renal pelvis
Ureter
Bladder
Urethra

12. Ureters 3 layers thick Middle layer is smooth muscle
Peristalsis propels urine

13. Bladder Hollow, distensible, muscular organ Stores urine
Internal urethral sphincter (smooth muscle)
Prevents bladder from emptying
Distention of the bladder triggers micturition reflex
Micturition = urination (expel urine from bladder)
External urethral sphincter
Skeletal muscle (conscious control)

14. Bladder Volumes 150 mL = urge to micturate begins (0.63 cup)
300 mL = urge intensifies (1.26 cups)
600 mL = stimulate pain receptors (2.54 cups)
Produce between 0.6 – 2.5 liters/day (2.54 – cups)

15. Urethra Tube from bladder to outside
Female = 4 cm / anterior to vaginal opening
Functions only in urination
Male = from bladder to tip of penis
Used for urinary and reproductive purposes

16. Urine Urine output of 50-60 milliliters per hour is normal
The usual amount of urine voided at one time is about 150 ml

17. Kidney Failure
Kidney failure can become life threatening as toxic wastes build up in the blood.
If kidneys fail - there are only two options:
hemodialysis - blood passes through dialysis machine which cleans it of toxins every two or three days (new dialysis techniques are being developed to clean blood more frequently)
transplant - rejection can occur if immune system is not suppressed with cyclosporin (drugs used to suppress immune system)

19. Disorders/Diseases Anuria- absence of urine formation
Cystitis - inflammation of the urinary bladder.
Fistula – abnormal connection between the urethra and bladder.
Hematuria - presence of blood, specifically red blood cells, in the urine.
Polyuria - passage of large volumes of urine
Nephrectomy – Removal of kidney
Kidney stones – solid concentrations formed in the kidney’s from dissolved urinary materials.