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The structure and function of the epithelial cells lining the lumen change during the course of the nephron, and have segments named by their location and which reflects their different functions. Fig.4) Diagram outlining movement of ions in nephron, with the collecting ducts on the right.
Each adult human kidney contains around 1 million nephrons, while a mouse kidney contains only about 12,500 nephrons. The kidneys also carry out functions independent of the nephrons. For example, they convert a precursor of vitamin D to its active form, calcitriol; and synthesize the hormones erythropoietin and renin.
The kidney has many functions, which a well-functioning kidney realizes by filtering blood in a process known as glomerular filtration. A major measure of kidney function is the glomerular filtration rate (GFR). The glomerular filtration rate is the flow rate of filtered fluid through the kidney.
The simplest nephrons are found in the pronephros, which is the final functional organ in primitive fish. [19] The nephrons of the mesonephros, the functional organ in most anamniotes called opisthonephros, [20] are slightly more complex than those of the pronephros. [19]
The body is very sensitive to its pH. Outside the range of pH that is compatible with life, proteins are denatured and digested, enzymes lose their ability to function, and the body is unable to sustain itself. The kidneys maintain acid-base homeostasis by regulating the pH of the blood plasma. Gains and losses of acid and base must be balanced.
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 human urinary system, also known as the urinary tract or renal system, consists of the kidneys, ureters, bladder, and the urethra.The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, control levels of electrolytes and metabolites, and regulate blood pH.
Blood tests are also used to assess kidney function. These include tests that are intended to directly measure the function of the kidneys, as well as tests that assess the function of the kidneys by looking for evidence of problems associated with abnormal function. One of the measures of kidney function is the glomerular filtration rate (GFR).