Jump to content

Renal medulla

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Tom.Reding (talk | contribs) at 17:50, 27 November 2018 (+{{Authority control}} (1 source from Wikidata), WP:GenFixes on). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Renal medulla
Vertical section of kidney. (Label "medullary sub." visible near top.)
Details
SystemUrinary system
Identifiers
LatinMedulla renalis
MeSHD007679
TA98A08.1.01.020
TA23369
FMA74268
Anatomical terminology

The renal medulla is the innermost part of the kidney. The renal medulla is split up into a number of sections, known as the renal pyramids. Blood enters into the kidney via the renal artery, which then splits up to form the interlobar arteries. The interlobar arteries each in turn branch into arcuate arteries, which in turn branch to form interlobular arteries, and these finally reach the glomeruli. At the glomerulus the blood reaches a highly disfavourable pressure gradient and a large exchange surface area, which forces the serum portion of the blood out of the vessel and into the renal tubules. Flow continues through the renal tubules, including the proximal tubule, the Loop of Henle, through the distal tubule and finally leaves the kidney by means of the collecting duct, leading to the renal pelvis, the dilated portion of the ureter.

The renal medulla (Latin renes medulla = kidney middle) contains the structures of the nephrons responsible for maintaining the salt and water balance of the blood. These structures include the vasa rectae (both spuria and vera), the venulae rectae, the medullary capillary plexus, the loop of Henle, and the collecting tubule.[1] The renal medulla is hypertonic to the filtrate in the nephron and aids in the reabsorption of water.

Blood is filtered in the glomerulus by solute size. Ions such as sodium, chloride, potassium, and calcium are easily filtered, as is glucose. Proteins are not passed through the glomerular filter because of their large size, and do not appear in the filtrate or urine unless a disease process has affected the glomerular capsule or the proximal and distal convoluted tubules of the nephron.

Though the renal medulla only receives a small percentage of the renal blood flow, the oxygen extraction is very high, causing a low oxygen tension and more importantly, a critical sensitivity to hypotension, hypoxia, and blood flow.[2] The renal medulla extracts oxygen at a ratio of ~80% making it exquisitely sensitive to small changes in renal blood flow. The mechanisms of many perioperative renal insults are based on the disruption of adequate blood flow (and therefore oxygen delivery) to the renal medulla.[2]

Additional Images

See also

References

  1. ^ Netter's, plate 337
  2. ^ a b Miller's Anesthesia, 8th edition. 553-554.