Question

Filtration fraction is the ratio of-
a. Glomerular filtration rate (GFR) and renal plasma flow (RPF)
b. Transport maximum ($Tm$) and clearance factor ($Cf$)
d. Hb and $HbO_2$
d. $O_2$ and $CO_2$

Answer 1

Hint: The filtration fraction usually constitutes about 20 percent of the proportion of fluid that passes through the renal tubules reaching the kidneys. If needed to execute the kidney's normal functions, it must be increased.

Complete answer:
> Option A is correct. The fraction of filtration reflects the proportion of fluid flowing through the renal tubules hitting the kidney. It is the measure of glomerular filtration rate (GFR) and renal plasma flow (RPF). Extreme haemorrhage is represented by increased filtration fraction.

> Option B is incorrect. Transport limit ($Tm$) represents the point at which changes in concentration of a substance do not result in an increase in movement of a substance through a cell membrane. The GFR is equal to the renal clearance of a substance ($Cf$) which is neither reabsorbed nor secreted by the tubules.

> Option C is incorrect. A protein found in red blood cells, haemoglobin. In order to maintain basic life functions, Haemoglobin's primary role is to transport oxygen from the lungs to body tissues. Hemoglobin, the largest portion of red blood cells, is responsible for bringing oxygen into the blood. In order to generate the energy needed for cell survival, it transports mainly into the lungs and releases it into tissues.

> Option D is incorrect. The exchange of gas is the delivery to the bloodstream of oxygen from the lungs and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs between the alveoli and a network of small blood vessels called capillaries in the lungs, which are situated in the alveoli 's walls.

Hence, the correct answer is option (A).

Note: The most common and significant indicator of renal function is GFR on its own. Blood flow to the kidneys, however, is reduced in conditions such as renal artery stenosis. Therefore, to perform the normal functions of the kidney, the filtration fraction must be increased. Filtration fraction is reduced by loop diuretics and thiazide diuretics.