Question

The diagram given below represents a nephron and its blood supply. Study the diagram and answer the following questions

(ii) State the reason for the high hydrostatic pressure in the glomerulus.

Answer 1

• The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere.
• The reason for this greater pressure is that the efferent or outgoing arteriole is having a narrower diameter than the afferent or incoming arteriole.
• So, when the blood moves into the efferent arterioles, their smaller diameter causes more resistance to blood flow which results in blood being pushed back into the glomeruli creating a higher pressure in the glomerular cavity.
• This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule.
• This filtration under great pressure is called ultrafiltration.