Question

Glomerular capillaries are drained by efferent arterioles whose diameter is smaller than the afferent arterioles that feed them; this creates the high blood pressure that drives filtration.

True

False

Answer 1

True

Glomerular filtration is happening due to the high glomerular blood hydrostatic pressure (GBHP). It is the Blood pressure in Glomerular capillaries and GBHP is 55 mmHg in humans. The forces opposing the filtration are Capsular Hydrostatic Pressure (CHP) and Blood Colloid Osmotic Pressure (BCOP). The CHP is 15 mmHg and BCP is 30 mmHg

Hence the net filtration pressure is

GBHP- CHP-BCOP = 55mmHg-15mmHg-30mmHg = 10 mmHg

The maintenance of this Net Filtration Pressure is essential for Urea formation and this is mainly maintained by the efferent arteriole. Due to the lesser diameter of the efferent arteriole, constant maintenance of GBHP is happening. If the blood flow is low, the Efferent arteriole will constrict and if the blood flow is high, the efferent arteriole will dilate to maintain the constant GBHP. Hormones like Angiotensin can regulate the diameter of efferent arteriole.