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The renal medulla (Latin: medulla renis 'marrow of the kidney') 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 segmental arteries which then branch to form interlobar arteries.
Before reaching the hilus of the kidney, each artery divides into four or five branches. The anterior branches (the upper, middle, lower and apical segmental arteries) lie between the renal vein and ureter, the vein being in front, the ureter behind. The posterior branches, which are fewer in number and include the posterior segmental artery ...
The kidneys in mammals are usually bean-shaped [4] or externally lobulated. [5] They are located behind the peritoneum (retroperitoneally) [6] on the back wall of the body. [7] The typical mammalian kidney consists of a renal capsule, a peripheral cortex, an internal medulla, one or more renal calyces, and a renal pelvis. [7]
The nephron is the functional unit of the kidney. [3] This means that each separate nephron is where the main work of the kidney is performed. A nephron is made of two parts: a renal corpuscle, which is the initial filtering component, and; a renal tubule that processes and carries away the filtered fluid. [4]: 1024
The kidney is directed to excrete or retain sodium via the action of aldosterone, antidiuretic hormone (ADH, or vasopressin), atrial natriuretic peptide (ANP), and other hormones. Abnormal ranges of the fractional excretion of sodium can imply acute tubular necrosis or glomerular dysfunction.
The vasa recta of the kidney, (vasa recta renis) are the straight arterioles, and the straight venules of the kidney, – a series of blood vessels in the blood supply of the kidney that enter the medulla as the straight arterioles, and leave the medulla to ascend to the cortex as the straight venules.
The renal cortex is the outer portion of the kidney between the renal capsule and the renal medulla. [1] In the adult, it forms a continuous smooth outer zone with a number of projections (cortical columns) that extend down between the pyramids.
[citation needed] A large "staghorn" kidney stone may block all or part of the renal pelvis. The size of the renal pelvis plays a major role in the grading of hydronephrosis . Normally, the anteroposterior diameter of the renal pelvis is less than 4 mm in fetuses up to 32 weeks of gestational age and 7 mm afterwards. [ 2 ]