Question

If the afferent arterioles diameter is less than efferent arterioles, then which of the following conditions is possible?
A. No effect
B. Ultrafiltration reaction is slow
C. Ultrafiltration is not possible
D. Ultrafiltration will stop and tubular secretion will start

Answer 1

Hint: The afferent arteriole is the arteriole that brings blood to the glomerulus. It is larger in diameter than the efferent arteriole. The efferent arteriole is the arteriole that carries blood away from the glomerulus. It is smaller in diameter than the afferent arteriole. These both the arterioles are found in the Bowman’s capsule.

Complete answer: Bowman’s capsule: It is a cup-like structure from which the renal tubule begins. It encloses the glomerulus. Malphigian body or renal corpuscle consists of Glomerulus and Bowman’s capsule. The tubule continues to form a highly coiled network of-
1. PCT: Proximal convoluted tubule.
2. Loop of Henle
3. DCT: Distal convoluted tubule
Afferent and efferent arterioles are located within the Bowman’s capsule. Afferent arterioles supply the blood to the Bowman’s capsule whereas the efferent arteriole exits the blood from the Bowman’s capsule.
Efferent arteriole carries the blood away from the glomerular because the diameter is smaller than afferent arteriole, they cause resistance to the flow of blood which produces backflow which results in high pressure. If the afferent arteriole diameter is less than the efferent arteriole then the ultrafiltration will not occur.
So, the correct option is option C. Ultrafiltration is not possible.

Note: The efferent arteriole emerges from the glomerulus forms a fine capillary network around the renal tubule called the peritubular capillaries. A minute vessel of this network runs parallel to the loop of Henle forming a ‘U’ shaped vasa rectum.