Renal medulla

Anatomy
The medulla of the kidney is darker, striated and sometimes reaches the hilum. It is stored under the outer layer of the bark.
 * pars radiata corticis - narrow strips of marrow extending deep into the cortex
 * is arranged in pyramidal (triangular in cross section) formations – pyramides renales, the base of each pyramid is turned towards the surface of the kidney and the top of the pyramid - papilla renalis is turned towards the hilum and penetrated by openings (area cribrosa) - foramina papillaria, which represent the mouths of drainage ducts - ductus papillares

The boundary between the bark and the pith is not straight.

Histological image

 * Loop of Henle
 * thin arm – single-layer flat epithelium, very thin wall, small lumen
 * thick shoulder – single-layer cubic epithelium, round, oval, regular lumen
 * collecting ducts - single-layer cubic epithelium, but the lumen is not so regular, there are visible boundaries between individual cells
 * other visible structures of the marrow: capillaries, arteries, veins, unmyelinated vegetative nerves,...

Related Articles

 * Kidneys
 * Nephron
 * Renal cortex