Kidney how it work
Kidney how it work
The kidney is very important organ
It supplied about 20 % of cardiac output
Cardiac output is about 72 ml per peat, 72 peat per min average 5200 ml per minute
Renal blood flow is about 1-1.2 L/min enter the kidney, most of it 90 % goes to the cortex
Renal plasma flow equal Renal blood flow (1 – Ht), it is about 500 – 600 mL/mi
Glomerular filtration rate equal About 20 % of Renal blood flow (filtration fraction) 100 – 120 mL/min
The kidneys maintains semi constant glomerular filtration rate by some mechanisms
here illustration
Glomerular filtration rate depend on:
glomerular hydrostatic pressure (= 60 mmHg). It promotes filtration.
hydrostatic pressure in Bowman’s capsule (= 18 mmHg). It opposes filtration.
colloid osmotic pressure of glomerular plasma proteins (= 32 mmHg). It opposes filtration.
Net Filtration Pressure (NFP) = 60-18-32= 10 mmHg.
The endothelium of capillary
Filtration slits of epithelial lining of bowman capsule (Podocytes)
Basement membrane (high negatively charge due to presence of proteoglycans)
* Effect of glomerular hydrostatic pressure
increase Arterial blood pressure (slightly affect due to autoregulation)
Afferent arteriole vasodilation
Moderate efferent arteriole vasoconstriction(1).
Afferent arteriole vasoconstriction
Efferent arteriole vasodilation
* Effect of hydrostatic pressure in Bowman’s capsule
* Effect of colloid osmotic pressure of glomerular plasma proteins
Dehydration
Decrease renal blood flow
Severe efferent vasoconstriction
Hypoproteinemia
increase renal blood flow
Autoregulation of GFR and Renal Blood Flow
