Renal medulla

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 splits apart to form the arcuate arterioles. The arcuate arterioles each in turn branch off to form several interlobular arterioles, which finally reach the glomeruli. At the glomerulus the blood reaches a highly disfavourable pressure gradient and a large exchange surface area, forcing 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 way of the collecting duct, leading into the renal pelvis, the ureter, and finally the bladder.

Structure

The renal medulla contains the structures of the nephrons responsible for maintaining the balance of water and salts in the blood. These structures include the vasa recta (the blood vessels that supply the medulla), the Loop of Henle, and the collecting ducts. The renal medulla is hypertonic to the filtrate in the nephron and aids in the reabsorption of water.

Function

The primary role of the renal medulla is to concentrate the salt in the interstitium, the tissue surrounding the loop of Henle, which helps in the reabsorption of water from the tubular fluid (pre-urine) back into the bloodstream. This concentration of salt is achieved by the loop of Henle's countercurrent multiplier system.

Clinical significance

Diseases of the renal medulla are quite common, including renal medullary carcinoma, renal medullary necrosis, and renal medullary cystic disease. These diseases can lead to kidney failure and can be fatal if not treated promptly.

See also

• Kidney
• Renal cortex
• Renal pyramid
• Nephron
• Renal artery
• Renal vein
• Renal capsule
• Renal column
• Renal pelvis
• Ureter
• Bladder

Renal_medulla

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