In the lower 40% of the inner medulla, AQP1 expression is relatively low or absent in most descending thin limb segments of the inner medulla of rat, chinchilla, and kangaroo rat, and in descending vasa recta in the lower 40% of the inner medulla of rat and kangaroo rat (Chou et al.
The collective histotopography of inner medullary, AQP 1-positive and AQP 1-negative descending thin limbs, and vasa recta and their different water permeabilities is important for reducing the fluid load delivered to the deep inner medulla, and is related to the distinct contributions of these segments to the production of the corticomedullary osmotic gradient (Layton et al.
Persson, "Iodixanol, constriction of medullary descending vasa recta, and risk for contrast medium-induced nephropathy," Radiology, vol.
Intrinsic nitric oxide and superoxide production regulates descending vasa recta contraction," American Journal of Physiology--Renal Physiology, vol.
Due to their mesenteric location, simple diverticulectomy may impair blood flow due to damage to vasa recta
and therefore may lead to anastomotic breakdown or fistula formation4-6.
The vasa recta
of the small bowel seen in Crohn's disease become tortuous and enlarged.
A dense capillary bed projects within the medulla between the afferent (descending) and efferent (ascending) vasa recta.
The arrangement of the tubule vasculature helps the nephrons concentrate or dilute fluid by creating a countercurrent exchange between the solute and water-rich fluid within the tubule (coming from the Bowman's capsule) and the solute-and water poor descending vasa recta (and proximal capillaries) coming from the glomerulus.
Medullar hypoxia is therefore mainly caused by CM effects on the medullary vessels themselves, in particular, on the long and narrow vasa recta.
First, as mentioned above, viscosity-induced increase in tubular pressure probably compresses the vasa recta [53, 56].
These wedges are the renal pyramids formed by the long loops of Henle, medullary collecting tubules, and vasa recta
Within the outer medulla, a peculiar gradient of hypoxic injury is noted, increasing from the better oxygenated region around vasa recta
to the mid-interbundle zone, most remote from oxygen supply [1,12].