Scheme of renal tubule and its vascular supply. (Label "Afferent vessel" is visible in upper left.)
Distribution of bloodvessels in cortex of kidney.
|Latin||arteriola glomerularis afferens|
The afferent arterioles are a group of blood vessels that supply the nephrons in many excretory systems. They play an important role in the regulation of blood pressure as a part of the tubuloglomerular feedback mechanism.
When renal blood flow is reduced (indicating hypotension) or there is a decrease in sodium or chloride ion concentration, the macula densa of the distal tubule releases prostaglandins (mainly PGI2 and PGE2) and nitric oxide, which cause the juxtaglomerular cells lining the afferent arterioles to release renin, activating the renin–angiotensin–aldosterone system, to increase blood pressure and increase reabsorption of sodium ions into the bloodstream via aldosterone.
If the afferent arterioles are constricted then the blood pressure in the capillaries of the kidneys will drop.