kidney

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Related to enlarged kidney: polycystic kidney disease

kidney

1. either of two bean-shaped organs at the back of the abdominal cavity in man, one on each side of the spinal column. They maintain water and electrolyte balance and filter waste products from the blood, which are excreted as urine
2. the corresponding organ in other animals
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Kidney

An organ involved with the elimination of water and waste products from the body. In vertebrates the kidneys are paired organs located close to the spine dorsally in the body cavity. They consist of a number of smaller functional units called urinary tubules or nephrons. The nephrons open to large ducts, the collecting ducts, which open into a ureter. The two ureters run backward to open into the cloaca or into a urinary bladder. In mammals, the kidneys are bean-shaped and found between the thorax and the pelvis. The number, structure, and function of the nephrons vary with evolution and, in certain significant ways, with the adaptation of the animals to their various habitats.

In its most primitive form, found only in invertebrates, the nephron has a funnel opening into the coelomic cavity followed by a urinary tubule leading to an excretory pore. In amphibians, some of the tubules have this funnel, but most of the tubules have a Bowman capsule (see illustration). In all higher vertebrates, the nephron has the Bowman capsule, which surrounds a tuft of capillary loops, called the glomerulus, constituting the closed end of the nephron. The inner epithelial wall of the Bowman capsule is in intimate contact with the endothelial wall of the capillaries. The wall of the capillaries, together with the inner wall of the Bowman capsule, forms a membrane ideally suited for filtration of the blood.

Nephron from frog kidney, dissected to show glomerulus within Bowman capsuleenlarge picture
Nephron from frog kidney, dissected to show glomerulus within Bowman capsule

The blood pressure in the capillaries of the glomerulus causes filtering of blood by forcing fluid, small molecules, and ions through the membrane into the lumen of Bowman's capsule. This filtrate contains some of the proteins and all of the smaller molecules in the blood. As the filtrate passes down through the tubule, the walls of the tubule extract those substances not destined for excretion and return them to the blood in adjacent capillaries. Many substances which are toxic to the organism are moved in the opposite direction from the blood into the tubules. The urine thus produced by each nephron is conveyed by the collecting duct and ureter to the cloaca or bladder from which it can be eliminated.

In all classes of vertebrates the renal arteries deliver blood to the glomeruli and through a second capillary net to the tubules. The major blood supply to the kidney tubules comes, however, from the renal portal vein, which is found in all vertebrates except mammals and cyclostomes. Waste products from the venous blood can thus be secreted directly into the urinary tubules. See Urinary system

kidney

[′kid·nē]
(anatomy)
Either of a pair of organs involved with the elimination of water and waste products from the body of vertebrates; in humans they are bean-shaped, about 5 inches (12.7 centimeters) long, and are located in the posterior part of the abdomen behind the peritoneum.
References in periodicals archive ?
Except in the patients with massively enlarged kidneys, PD is a viable method of renal replacement therapy with a good outcome in PKD patients.
2) revealed grossly enlarged kidneys with compressed renal sinuses.
Cases of HIVAN included HIV-infected patients with renal biopsies consistent with HIVAN and probable cases with (i) enlarged kidneys by ultrasound or radiographic imaging; (ii) nephrotic range proteinuria (>3.
Dad Ken, 65, said an autopsy on one of the cats had revealed grossly enlarged kidneys - a tell-tale sign of antifreeze poisoning.
The renal ultrasound report from November 2007 reveals multiple small cysts with bilaterally mildly enlarged kidneys.
As her daughter was born with enlarged kidneys, she has to take her to Cairo for tests and treatment every four to five months-- a far cry from the monthly treatment the girl used to receive in Iraq.
The organs presented normal anatomical relatiolas with enlarged kidneys and an enlarged liver that extended 9 cm below the right costal border at the midclavicular line.
In the CT of the abdomen, a thickened wall of the colon ascendens, an enlarged caecum, slightly enlarged kidneys, approximately 500 mL of ascites, and enhancement of the peritoneum were found.
The presence of hyperechoic enlarged kidneys without associated malformations is most frequently associated with polycystic kidney disease (Both autosomal recessive and dominant).
Kidney size was available in 181 cases; 69 cases (~38%) were associated with enlarged kidneys (8 of which had sizes 2 standard deviations above the mean for age), whereas in 38 cases (~20%) the kidneys were small for age.
If a baby has the disease it is usually identified soon after birth when the enlarged kidneys cause the abdomen to swell.
They also had high blood pressure, shrunken livers and enlarged kidneys.