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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.
In the human urinary system there are two kidneys that are located between the dorsal body wall and parietal peritoneum on both the left and right sides. The formation of urine begins within the functional unit of the kidney, the nephrons. Urine then flows through the nephrons, through a system of converging tubules called collecting ducts.
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.
Avian kidneys combine so called reptilian-type nephrons, without the loop of Henle, and mammalian-type nephrons, with the loop of Henle. [23] Most nephrons are reptilian-type. [ 84 ] The loop of Henle of birds is similar to that of mammals, the main difference is that the nephron of birds has only a short loop of Henle. [ 77 ]
In mice, the kidneys are approximately 1 cm (0.4 in) long, weighing 400 mg, with 16,000 nephrons, while in the killer whale, the kidney length exceeds 25 cm (10 in), the mass is approximately 4.5 kg (10 lb), with the number of nephrons of the order of 10,000,000. At the same time, the killer whale kidneys are reniculate, with each renicule ...
Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood pressure; production of various hormones, such as erythropoietin; and activation of vitamin D.
The collecting duct system of the kidney consists of a series of tubules and ducts that physically connect nephrons to a minor calyx or directly to the renal pelvis.The collecting duct participates in electrolyte and fluid balance through reabsorption and excretion, processes regulated by the hormones aldosterone and vasopressin (antidiuretic hormone).