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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.
Upon presentation of decreased renal function, it is recommended to perform a history and physical examination, as well as performing a renal ultrasound and a urinalysis. [ citation needed ] The most relevant items in the history are medications , edema , nocturia , gross hematuria , family history of kidney disease, diabetes and polyuria .
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 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.
The main difference between the pronephros and the mesonephros is that the pronephros consists of non-integrated nephrons with external glomeruli. [7] The most complex nephrons are found in the metanephros of birds and mammals. [19] [21] [22] The kidneys of birds and mammals have nephrons with loop of Henle. [23]
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 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 ...