http://purl.obolibrary.org/obo/NCBITaxon_9606

Note that 'renal medulla' is not synonymous with 'medullary region of kidney'. The former is composed of kidney pyramids only, while the latter covers kidney pyramids and renal columns, which are histologically different.

https://upload.wikimedia.org/wikipedia/commons/6/69/Illu_kidney.jpg

uberon

renal marrow, medullary pyramids

UBERON:0000362

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 arcuate arterioles. The arcuate arterioles each in turn branch into interlobular arterioles, which 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 into the renal tubules. Flow continues through the renal tubules, including the proximal tubule, the Loop of Henle, and finally leaves the kidney by means of the collecting duct, leading to the renal ureter. The renal medulla contains the structures of the nephrons responsible for maintaining the salt and water balance of the blood. The renal medulla is hypertonic to the filtrate in the nephron and aids in the reabsorption of water

• kidney pyramid