Vasa rectae

Straight arterioles
A nephron, the vasa recta are labeled arteriolae rectae
Details
Source	efferent arteriole
Branches	Straight venules of kidney, arcuate vein
Identifiers
Latin	arteriolae rectae renis
Dorlands /Elsevier	Vasa recta renis
TA	A08.1.03.008
FMA	72006
Anatomical terminology []

In the blood supply of the kidney, the straight arterioles of kidney (or vasa recta renis) are a series of straight capillaries in the medulla (Latin: vasa, "vessels"; recta, "straight"). They lie parallel to the loop of Henle.

These vessels branch off the efferent arterioles of juxtamedullary nephrons (those nephrons closest to the medulla), enter the medulla, and surround the loop of Henle. The straight arterioles are peritubular capillaries, specifically those that surround the loop of Henle.

On a histological slide, the straight arterioles can be distinguished from the tubules of the loop of Henle by the presence of blood.

Each straight arteriole has a hairpin turn in the medulla and carries blood at a very slow rate – two factors crucial in the maintenance of countercurrent exchange that prevent washout of the concentration gradients established in the renal medulla.

The maintenance of this concentration gradient is one of the components responsible for the kidney's ability to produce concentrated urine.

On the descending portion of the straight arterioles, NaCl and urea are reabsorbed into the blood, while water is secreted. On the ascending portion, NaCl and urea are secreted into the interstitium, while water is reabsorbed

The slow blood flow in the straight arterioles makes them a likely location of thrombosis in hypercoagulable states, or tissue loss due to erythrocyte sickling in sickle cell disease. Ischemia that results may lead to renal papillary necrosis.

According to Terminologia Anatomica, the term "vasa recta renis" is an alternate name for "arteriolae rectae renis", and a separate term, venulae rectae renis, is used to identify the venous portion.