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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 ...
As flow increases, the ability of the loop to maintain its osmolar gradient is reduced. The vasa recta (capillary loops) also have a slow flow as well. Increases in vasa recta flow wash away metabolites and cause the medulla to lose osmolarity as well. Increases in flow will disrupt the kidney's ability to form concentrated urine. [3]
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 collecting duct system is the final component of the kidney to influence the body's electrolyte and fluid balance. In humans, the system accounts for 4–5% of the kidney's reabsorption of sodium and 5% of the kidney's reabsorption of water. At times of extreme dehydration, over 24% of the filtered water may be reabsorbed in the collecting ...
The simplest type of kidney in mammals is the unipapillary kidney, consisting of a cortex, medulla, and renal pelvis. [163] But the unipapillary kidney is limited by the number of nephrons at which it functions optimally. [20] It is assumed that unipapillary kidney was the original kidney structure in mammals, from which multilobar kidneys ...
Each renal artery branches into segmental arteries, dividing further into interlobar arteries, which penetrate the renal capsule and extend through the renal columns between the renal pyramids. The interlobar arteries then supply blood to the arcuate arteries that run through the boundary of the cortex and the medulla.
The functional substance, or parenchyma, of the human kidney is divided into two major structures: the outer renal cortex and the inner renal medulla. Grossly, these structures take the shape of eight to 18 cone-shaped renal lobes, each containing renal cortex surrounding a portion of medulla called a renal pyramid. [18]
The kidney is responsible for about half of the total gluconeogenesis in fasting humans. The regulation of glucose production in the kidney is achieved by action of insulin, catecholamines and other hormones. [14] Renal gluconeogenesis takes place in the renal cortex. The renal medulla is incapable of producing glucose due to absence of ...