CorpusHuman Anatomy
UrinaryVessel

Afferent arteriole

Arteriola glomerularis afferens

Also known as: afferent glomerular arteriole

The small artery that carries blood from a cortical radiate artery into the glomerulus; its tone is the main regulator of glomerular blood flow and its wall contains the renin-secreting juxtaglomerular cells.

Show on body map Nephron — Juxtamedullary

Overview

Each afferent arteriole enters a renal corpuscle at the vascular pole and divides into the glomerular capillary tuft. Its smooth muscle responds to stretch (the myogenic response of autoregulation) and to signals from the macula densa (tubuloglomerular feedback, via adenosine on A1 receptors), keeping GFR stable despite changes in blood pressure. Near the glomerulus, some of its smooth muscle cells are modified into granular juxtaglomerular (JG) cells that store and secrete renin.

Constriction of the afferent arteriole lowers glomerular capillary pressure, renal plasma flow and GFR; dilatation raises them. It is constricted by sympathetic (α1) stimulation, adenosine, endothelin and high-dose angiotensin II, and dilated by prostaglandins (PGE₂, PGI₂), nitric oxide, bradykinin and ANP.

Location

Renal cortex, from cortical radiate artery to glomerular vascular pole.

Anatomy

Histology

Endothelium, internal elastic lamina, 1–2 layers of smooth muscle; JG (epithelioid) cells with renin granules at the vascular pole.

Function

  • Deliver blood to the glomerulus at high pressure
  • Regulate glomerular capillary pressure and GFR (autoregulation)
  • House the renin-secreting juxtaglomerular cells (intrarenal baroreceptor)
Regulation

Myogenic reflex; tubuloglomerular feedback (macula densa → adenosine/ATP); sympathetic nerves; prostaglandins (vasodilator); ANP (dilator).

Clinical significance

NSAIDs and the kidney

In volume depletion, heart failure or cirrhosis, vasodilator prostaglandins keep the afferent arteriole open. NSAIDs block them → afferent constriction → fall in GFR (prerenal AKI), especially combined with ACE inhibitors and diuretics ("triple whammy").

Hyaline arteriolosclerosis

Thickened, hyalinised afferent arterioles in benign hypertension and diabetes reduce glomerular perfusion and cause nephrosclerosis; in diabetes both afferent and efferent arterioles are affected.

Compiled from standard anatomy and physiology references — see the Urinary System sources. For education only; not medical advice.