1. Human Urinary System/Excretory System
MAINTAINS HOMEOSTASIS….
Important for eliminating metabolic waste (waste produced from metabolism)
Maintains the appropriate water-salt balance in the blood
Maintains blood pressure
Maintains Acid-base balance
of blood
Secretes hormones

2. Organs of the Urinary System
Kidneys – 2
Ureters – 2
Urinary bladder -1
Urethra – 1
Lump of glandular
tissue on each kidney
these are the adrenal
glands.

3. Kidneys Main organs of the Urinary System
Bean shaped/reddish brown and fist sized
Covered by a tough capsule of connective tissue – called the renal capsule
Renal arteries bring blood to the kidneys
Renal veins carry blood
away from the kidneys
Anytime you see the
word renal – think kidneys

4. Ureters Extend from kidneys to bladder
Peristalsis of ureters cause urine to enter the bladder

5. UrinaryBladder Recieves urine from the ureters
Stores urine until it is expelled from the body
Urine enters the bladder in spurts – 1-5 spurts per minute.

6. Urethra
Small tube that extends from the bladder to an external opening
When the urinary bladder fills to about 250 ml of urine, stretch receptors and nerve impulses cause the urinary bladder to contract, sphincters to relax -and you pee.

7. Anatomy of the Kidney Cortex- outer layer
Medulla – middle that consists of tissue masses
Pelvis – central space that is continuous with the ureter
Each kidney is composed of over one million nephrons…

9. Nephrons (kidney tubules)
Each kidney is composed of over one million microscopic nephrons
Long, coiled tube with one cuplike end that fits over a mass of capillaries, the other end opens into a duct that collects urine.
Cup of nephron – Glomerulus capsule or Bowman’s capsule
Ball of capillaries within the cup - Glomerulus

10. 3 Functions of the nephron
Filtration
Reabsorbtion
Secretion

16. Filtration
Filtration: fluid portion of the blood is forced into the glomerular capsule (filtrate)
Happens in the glomerulus capsule
Water, salts, nutrients (glucose, amino acids, small proteins), nitrogenous waste (urea)
Blood cells and large blood proteins are NOT filtered

17. Reabsorption Reabsorption –absorbing again (into blood)
Cells of tubules reabsorb substances needed by the body from the filtrate.
happens in the proximal (close to the capsule) kidney tubules of nephron
Nutrients (glucose, amino acids) and salt molecules

18. Secretion
Secretion: Process of secreting a substance from the blood into the kidney tubules
Happens between the nephron capillaries and the distal (far away from capsule) kidney tubules of the nephron (countercurrent exchange)
Anything that wasn’t filtered at the glomerulus capsule or anything that was reabsorbed that shouldn’t have been
H+ ions, K+ ions, creatinine and drugs

20. 2. Substances that have undergone secretion
So Urine Contains:
1. Substances that have undergone filtration but have not been reabsorbed
2. Substances that have undergone secretion
Urea comes from the breakdown of amino acids.

21. Urea: CH4N2O
is the primary Nitrogenous end product of metabolism.
Amino acids broken down in the liver causing the liver to release ammonia- toxic to cells. The liver combines the ammonia with carbon dioxide to make urea – not toxic to cells and can be released in urine.
Creatinine: C4H9N3O2
High energy phosphate reserve molecule in muscles
Uric Acid: C5H4N4O3
From the breakdown of nucleic acids

23. More Kidney Functions Adrenal glands secrete the hormone Aldosterone
Aldosterone regulates excretion of sodium and potassium
When K+ levels are too high in the blood, aldosterone is released into the blood, stimulating the secretion of K+ ions from the blood into the tubule near the collecting duct lowering the aldosterone levels – feedback mechanism
More Kidney Functions

24. Aldosterone
Increases reabsorption of ions and water in the kidneys -- increasing blood volume… increasing blood pressure.

25. ADH
Dehydrated – brain secretes ADH (anti-diuretic hormone) so the cell membranes of the collecting ducts become more permeable to water. Water passes from the duct to the bloodstream and water volume in the blood is restored (higher blood pressure)

26. More Kidney functions
Removes excess salt from body – in small concentrations
When humans drink high salt solutions, the body loses water b/c while trying to eliminate the excess salt, the body excretes more water than taken in.