Which factors influence the rate of glomerular filtration?
Glomerular filtration rate is the amount of fluid that is filtered in one minute. Normal rate is about 125 ml/min. This factor is the best in revealing the level of kidney function. Factors that affect the glomerular filtration are glomerular hydrostatic pressure, glomerular colloidal osmotic pressure, and the hydrostatic pressure in the Bowman's capsule. Glomerular hydrostatic pressure in the glomerulus is about 60 mmHg, which is higher than in other capillaries in the body (20-25 mmHg). In the Bowman's capsule, it is about 18 mmHg which tells us that the water will go from the glomerulus to the capsular space. Colloid osmotic pressure is around 32 mm Hg.
Net filtration pressure = Glomerular hydrostatic pressure - Plasma colloid osmotic pressure - Capsular hydrostatic pressure
Glomerular filtration rate is directly proportional to the net filtration pressure. Various factors that affect glomerular hydrostatic pressure, plasma colloid pressure, or capsular hydrostatic pressure indirectly affect the glomerular filtration rate.
Glomerular filtration rate and net filtration pressure are directly proportional. The filtration rate is also influenced by the hydrostatic pressure and osmotic pressure within the glomerular capillaries and hydrostatic pressure within the glomerular capsule.
. An increase in the diameter of the afferent arteriole causes an increase in the glomerular capillary hydrostatic pressure and GFR. A decrease in its diameter has the opposite effect. . An increase in the diameter of the efferent arteriole causes a decrease in the glomerular capillary hydrostatic pressure and GFR. A decrease in its diameter has the opposite effect. . Hydrostatic pressure in the glomerular capsule and capillary osmotic pressure oppose filtration. Hence, this causes a decrease in the GFR.