Question

how is the glomerulus adapted adapted for filtration.

be specific please! and thank you

Answer 1

Glomerular filtration is the initial step of urine production in which the solutes and the water move to the glomerular capsule through the glomerular capillaries and then move into the renal tubules.

The glomerulus is adapted for filtration mainly in three ways.

1. The large surface area of the glomerular capillaries.

The glomerular capillaries have specialized cells called mesangial cells which regulate the surface area for filtration. When the mesangial cells are contracted, the available surface area for filtration reduced. If the cells are relaxed, The filtration is increased due to the increased surface area of filtration.

2. The structure of the filtration membrane.

The filtration membrane has three barriers which are arranged in a sandwich-like manner. The barriers are endothelial cells, the basal lamina, and the filtration slit. They are very thin and porous due to the large fenestrations which makes them very leaky compared to other capillaries. The structure allows filtration of solutes and water and prevents the passage of large molecules like proteins, and blood cells.

3. High glomerular capillary blood pressure.

Glomerular filtration depends on three pressures. The glomerular blood hydrostatic pressure which is the pressure in the glomerular capillaries that forces the solutes and water from the blood plasma to the glomerular capsule through the filtration membrane. it will be about 55 mmHg.The capsular hydrostatic pressure is the pressure exerted by the fluid present in the capsular space and renal tubule, against the filtration membrane which opposes the filtration. The pressure is usually 15 mmHg. The blood colloid osmotic pressure is the opposite pressure on filtration exerted by the large molecules like proteins. this pressure is about 30 mmHg.

The total pressure that promotes filtration is net filtration pressure.

Net filtration pressure = glomerular blood hydrostatic pressure - capsular hydrostatic pressure - blood colloid osmotic pressure

NFP = 55 mmHg - 15 mmHg - 30 mmHg = 10 mmHg

The NFT of 10 mmHg is the pressure for normal filtration.