Question

long answered question: 0.5-1 page long

What are the determinants of net filtration pressure and how does this relate to GFR?

Answer 1

The net filtration pressure is the sum of the hydrostatic and colloid osmotic pressures that either favorites or oppose filtration across the filtration membrane.

By the interaction of these forces net filtration pressure is determined:

1.Glomerular blood hydrostatic pressure (GBHP)

2.Capsular hydrostatic pressure (CHP)

3.Blood colloid osmotic pressure (BCOP)

The equation is: NFP=GBHP - (CHP+BCOP)

GLOMERULAR BLOOD HYDROSTATIC PRESSURE:- It is the pressure within the capillaries.Due to this mechanical pressure,it pushes the plasma filtrate from the capillaries of the glomerulus in to the capsular space.

CAPSULAR HYDROSTATIC PRESSURE:- CHP is the back pressure of the filtrate(like water or dissolved solutes) in the glomerular or Bowman's capsule.

BLOOD COLLOIDAL OSMOTIC PRESSURE:- It is the tendency of blood protein to draw water back in to the plasma in the glomerular capillaries.

**Net filtration pressure is usually around 10mmHg**

Glomerular filtration is the first step in the urine formation. Glomerular filtration rate is the volume of fluid filtered in the glomeruli. A healthy individual have GFR =120-125mL/min. GFR is determined by :

a) Net filtration pressure. b) Surface area available for filtration. c) Permeability of filtration membrane.

Net filtration pressure and glomerular filtration rate are directly proportional. GFR is mainly determined by net filtration pressure,as the NFP increases,GFR increases,as NFP decreases,GFR decreases.