Question

Which among the following factors facilitate ultrafiltration?

• A. Powerful pumping action of heart
• B. The glomerular capillaries are narrower than afferent arterioles.
• C. The glomerular capillaries are broader than afferent arterioles.
• D. both a and b are correct

Answer 1

The correct option is B The glomerular capillaries are narrower than afferent arterioles.

The diameter of afferent arteriole is larger than the diameter of glomerular capillaries. As a result there is high resistance as the blood is forced from a wider afferent arteriole to narrower glomerular capillaries and this promotes filtration.
The blood pressure in the glomerular capillaries becomes very high leading to continuous ultrafiltration (filtration under pressure) through semi permeable glomerular capillaries.