Question

Pressure which favours filtration and one which opposes filtration of blood are ________ respectively.

A. Capsular hydrostatic pressure and glomerular osmotic pressure
B. Glomerular hydrostatic pressure and glomerular osmotic pressure
C. Glomerular osmotic pressure and glomerular hydrostatic pressure
D. Glomerular osmotic pressure and arterial pressure

Answer 1

Hint: GFR determines how quickly the blood is filtered from metabolic waste, the effectiveness of the kidneys in tubular reabsorption and secretion, and how well kidneys are able in maintaining homeostasis in the body.

Complete answer:
Blood filtration is performed by the glomerulus and is termed glomerular filtration. It is the first step of urinary production. There are about a million complex tubular structures in each kidney, called nephrons, which are functional units. There are two sections of a nephron- the glomerulus and the renal tubule. Glomerulus is an afferent arteriole formed by a group of capillaries. The renal tubule begins with a double walled Bowman's capsule and is further divided into a proximal convoluted tubule (PCT), a loop of Henle (HL) and a convoluted distal tubule (DCT).

The volume of filtration produced by the kidneys in a minute is known as the glomerular filtration rate (GFR). In a normal healthy person, the GFR is roughly 125 ml/minute. Hydrostatic pressure and colloid osmotic pressure on each side of the glomerular capillary membrane influences the glomerular filtration rate. The pressure generated by the fluid against the surface is called hydrostatic pressure. Osmosis is the passage of a liquid across a membrane that is impermeable to a solvent in a solution. Glomerular filtration happens as glomerular hydrostatic pressure approaches the luminal hydrostatic pressure of the Bowman capsule. There is also an opposite force, the osmotic strain, which is normally stronger in the glomerular capillary.

Hence, the correct answer is option (B)

Note: The kidneys are capable of filtering blood so effectively partly because the glomerular capillaries are surprisingly permeable. However, and for fenestrated capillaries, filtration can only occur where there is a pressure gradient to force water to dissolve through the filtration membrane.