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The glomerulus (pl.: glomeruli) is a network of small blood vessels (capillaries) known as a tuft, located at the beginning of a nephron in the kidney. Each of the two kidneys contains about one million nephrons. The tuft is structurally supported by the mesangium (the space between the blood vessels), composed of intraglomerular mesangial cells.
Diagram of the circulation related to a single glomerulus, associated tubule, and collecting system The renal corpuscle in the cortex (outer layer) of the kidney. At the top, the renal corpuscle containing the glomerulus. The filtered blood exits into the renal tubule as filtrate, at right. At left, blood flows from the afferent arteriole (red ...
Bowman's capsule (or the Bowman capsule, capsula glomeruli, or glomerular capsule) is a cup-like sac at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine. A glomerulus is enclosed in the sac. Fluids from blood in the glomerulus are collected in the ...
[17] [6] [18] Differences in kidney structure are the result of adaptations during evolution to variations in body mass and habitats (in particular, aridity) between species. [19] [20] [12] The cortex and medulla of the kidney contain nephrons, [21] each of which consists of a glomerulus and a complex tubular system. [22]
Proper function of the kidney requires that it receives and adequately filters blood. This is performed at the microscopic level by many hundreds of thousands of filtration units called renal corpuscles, each of which is composed of a glomerulus and a Bowman's capsule.
The glomeruli in reptiles have also decreased in size compared to amphibians. [52] In addition to the renal artery blood supply, reptiles also have a renal portal system, which can redirect blood to the kidneys during periods of water deprivation, bypassing the glomeruli, to prevent ischemic necrosis of tubular cells. [21] [57]
The structures of the layers of the glomerulus determine their permeability-selectivity (permselectivity). For instance, small ions such as sodium and potassium pass freely, while larger plasma proteins, such as hemoglobin tetramers, haptoglobin bound hemoglobin and albumin have practically no permeability at all. Also, negatively charged ...
People have variations in these proteins, and some variations may predispose them to kidney failure later in life. Nephrin is a zipper-like protein that forms the slit diaphragm, with spaces between the teeth of the zipper big enough to allow sugar and water through but too small to allow proteins through.