Afferent arterioles

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Afferent arterioles
Scheme of renal tubules and its vascular supply. (Label "Afferent vessel" is visible in upper left.)
Distribution of bloodvessels in cortex of kidney.
Details
From	interlobular artery
Supplies	glomerular capillaries
Identifiers
Latin	arteriola glomerularis afferens
TA98	A08.1.03.005
FMA	272216 77042, 272216
Anatomical terminology [edit on Wikidata]

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.

The afferent arterioles branch from the renal artery, which supplies blood to the kidneys.

The afferent arterioles later diverge into the capillaries of the glomerulus.

Regulation

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.^[1]

The macula densa cell can also increase the blood pressure of the afferent arterioles by decreasing the synthesis of adenosine or ATP.^[1]

If the efferent arterioles are constricted then the blood pressure in the capillaries of the kidneys will increase.

^ ^a ^b Peti-Peterdi, János; Harris, Raymond C. (2010). "Macula Densa Sensing and Signaling Mechanisms of Renin Release: Figure 1". Journal of the American Society of Nephrology. 21 (7): 1093–1096. doi:10.1681/ASN.2009070759. PMC 4577295. PMID 20360309.

Nosek, Thomas M. "Section 7/7ch03/7ch03p10". Essentials of Human Physiology. Archived from the original on 2016-03-24. - "Renal Vasculature: Efferent Arterioles & Peritubular Capillaries"
Anatomy photo: Urinary/mammal/vasc0/vasc2 - Comparative Organology at University of California, Davis - "Mammal, renal vasculature (EM, Low)"

Anatomy of the urinary system

Layers

Renal corpuscle	Glomerulus Bowman's capsule Glomerular basement membrane Podocyte Filtration slits Mesangium Intraglomerular mesangial cell
Renal tubule	Proximal convoluted tubule Loop of Henle Descending Thin ascending Thick ascending Distal convoluted tubule Collecting duct system Connecting tubule Papillary duct Tubular fluid Renal papilla Minor calyx Major calyx Renal pelvis
Juxtaglomerular apparatus	Macula densa Juxtaglomerular cells Mesangium Extraglomerular mesangial cell