1. Urine formation function of kidney.

4. Urine formation Structures responsible for the urine formation:
glomeruli,
proximal canaliculi,
distal canaliculi.
Mechanism of urine formation:
filtration
reabsorption
secretion 4

5. Mechanisms of elimination: filtration reabsorption excretion5

6. Filtration About 120 mL/min or 180 L/day of blood is filtrated.
Takes place in glomeruli.
Substances with molecular mass below 40,000 Da pass through the membrane of glomerulus into capsula.
About 120 mL/min or 180 L/day of blood is filtrated.
Filtration – passive process.
After filtration – primary urine (180 L/day) 6

7. Filtration is caused by:
-hydrostatic pressure of blood in capillaries of glomeruli (70 mm Hg)
-oncotic pressure of blood plasma proteins (30 mm Hg)
-hydrostatic pressure of ultrafiltrate in capsule (20 mm Hg)
70 mm Hg-(30 mm Hg+20 mm Hg)=20 mm Hg
Hydrostatic pressure in glomeruli is determined by the ratio between diameter of ascendant and descendant arteriole 7

8. Reabsorption Takes place in proximal and distal canaliculi.
What is reabsorbed? Glucose (100%), amino acids (93%), water (98%), NaCl (70%) etc.
The urine is concentrated (toxins damages the proximal canaliculi)
Reabsorption:
active
passive.
Lipophilic substances - passive.
Na/K АТP-аse is very active 8

9. Secretion Takes place in proximal and distal canaliculi. Secretion:
Transport of substances from blood into filtrate.
Takes place in proximal and distal canaliculi.
Secretion:
active
passive.
Passive secretion depends on the pH.
What is secreted?
Ions of K, аmmonia, H+
drugs
xenobiotics 9

10. CLEARANCE Clearance = (C urine/C plasma) * V
Clearance of any substance is expressed in ml of blood plasma that is purified from this substance for 1 min while passing through the kidneys.
About 180 L of primary urine is formed for 1 day, about 125 mL of primary urine for 1 min.
Glucose is reabsorbed completely; clearance = 0
Inulin is not reabsorbed absolutely; clearance = 125 mL/min
If clearance is more than 125 mL/min the substance is secreted actively.
Clearance = (C urine/C plasma) * V 10