Kidney
From Wikipedia, the free encyclopedia
| Kidney | |
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| Human kidneys viewed from behind with spine removed | |
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| Lamb kidneys | |
| Latin | ren |
| Gray's | subject #253 1215 |
| Artery | renal artery |
| Vein | renal vein |
| Nerve | renal plexus |
| MeSH | Kidney |
| Dorlands/Elsevier | Kidney |
The kidneys are paired organs, which have the production of urine as their primary function. Kidneys are seen in many types of animals, including vertebrates and some invertebrates. They are part of the urinary system, but have several secondary functions concerned with homeostatic functions. These include the regulation of electrolytes, acid-base balance, and blood pressure. In producing urine, the kidneys excrete wastes such as urea and ammonium; the kidneys also are responsible for the reabsorption of glucose and amino acids. Finally, the kidneys are important in the production of hormones including vitamin D and erythropoietin.
Located behind the abdominal cavity in the retroperitoneum, the kidneys receive blood from the paired renal arteries, and drain into the paired renal veins. Each kidney excretes urine into a ureter, itself a paired structure that empties into the urinary bladder.
Renal physiology is the study of kidney function, while nephrology is the medical specialty concerned with diseases of the kidney. Diseases of the kidney are diverse, but individuals with kidney disease frequently display characteristic clinical features. Common clinical presentations include the nephritic and nephrotic syndromes, acute kidney failure, chronic kidney disease, urinary tract infection, nephrolithiasis, and urinary tract obstruction.[1]
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[edit] Anatomy
[edit] Location
In humans, the kidneys are located behind the abdominal cavity, in a space called the retroperitoneum. There are two, one on each side of the spine; they are approximately at the vertebral level T12 to L3.[2] The right kidney sits just below the diaphragm and posterior to the liver, the left below the diaphragm and posterior to the spleen. Above each kidney is an adrenal gland (also called the suprarenal gland). The asymmetry within the abdominal cavity caused by the liver typically results in the right kidney being slightly lower than the left, and left kidney being located slightly more medial than the right.[citation needed] The upper (cranial) parts of the kidneys are partially protected by the eleventh and twelfth ribs, and each whole kidney and adrenal gland are surrounded by two layers of fat (the perirenal and pararenal fat) and the renal fascia. Each adult kidney weighs between 125 and 170 g in males and between 115 and 155 g in females.[2] The left kidney is typically slightly larger than the right.[citation needed]
[edit] Structure
Bean-shaped structures, each kidney has concave and convex surfaces. The concave surface, the renal hilum, is the point at which the renal artery enters the organ, and the renal vein and ureter leaves. The kidney is surrounded by tough fibrous tissue, the renal capsule, which is itself surrounded by perinephric fat, renal fascia (of Gerota), and paranephric fat. The anterior (front) border of these tissues is the peritoneum, while the posterior (rear) border is the transversalis fascia.
The substance, or parenchyma, of the kidney is divided into two major structures: superficial is the renal cortex and deep is the renal medulla. Grossly, these structures take the shape of 8 to 18 cone-shaped renal lobes, each containing renal cortex surrounding a portion of medulla called a renal pyramid (of Malphigi).[2] Between renal pyramids, which are composed of medulla, are projections of cortex called renal columns (of Bertin). Nephrons, the urine-producing functional structures of the kidney, span the cortex and medulla. The initial filtering portions of the nephron, the renal corpuscles, are located in the cortex and each sends a renal tubule that passes from the cortex deep into the medullary pyramids. Part of the renal cortex, a medullary ray is a collection of renal tubules that drain into a single collecting duct.
The tip, or papilla, of each pyramid empties urine into a minor calyx, minor calyces empty into major calyces, and major calyces empty into the renal pelvis and ultimately the ureter and urinary bladder. These urine-filled spaces comprise the renal sinus.[2]
[edit] Blood supply
The kidneys receive blood from the renal arteries, left and right, which branch directly from the abdominal aorta. Despite their relatively small size, the kidneys receive approximately 20% of the cardiac output.[2]
Each renal artery branches into segmental arteries, dividing further into interlobar arteries which penetrate the renal capsule and extend through the renal columns between the renal pyramids. The interlobar arteries then supply blood to the arcuate arteries that run through the boundary of the cortex and the medulla. Each arcuate artery supplies several interlobular arteries that feed into the afferent arterioles that supply the glomeruli.
After filtration occurs the blood moves through a small network of venules that converge into interlobular veins. As with the arteriole distribution the veins follow the same pattern, the interlobular provide blood to the arcuate veins then back to the interlobar veins which come to form the renal vein exiting the kidney for transfusion for blood.
[edit] Histology
Renal histology studies the structure of the kidney as viewed under a microscope. Various distinct cell types occur in the kidney, including:
- Kidney glomerulus parietal cell
- Kidney glomerulus podocyte
- Kidney proximal tubule brush border cell
- Loop of Henle thin segment cell
- Thick ascending limb cell
- Kidney distal tubule cell
- Kidney collecting duct cell
- Interstitial kidney cell
[edit] Embryology
The mammalian kidney develops from intermediate mesoderm. Kidney development, also called nephrogenesis, proceeds through a series of three successive phases, each marked by the development of a more advanced pair of kidneys: the pronephros, mesonephros, and metanephros.[3]
[edit] Evolutionary adaptation
Kidneys of various animals show evidence of evolutionary adaptation and have long been studied in ecophysiology and comparative physiology. Kidney morphology, often indexed as the relative medullary thickness, is associated with habitat aridity among species of mammals.[4]
[edit] Etymology
Medical terms related to the kidneys commonly use terms such as renal and the prefix nephro-. The adjective renal, meaning related to the kidney, is from the Latin rēnēs, meaning kidneys; the prefix nephro- is from the Ancient Greek word for kidney, nephros (νεφρός).[5] For example, surgical removal of the kidney is a nephrectomy, while a reduction in kidney function is called renal dysfunction.
[edit] Diseases and disorders
[edit] Congenital
- Congenital hydronephrosis
- Congenital obstruction of urinary tract
- Duplicated ureter
- Horseshoe kidney
- Polycystic kidney disease
- Renal agenesis
- Renal dysplasia
- Unilateral small kidney
- Multicystic dysplastic kidney
- Parenchyma
[edit] Acquired
- Diabetic nephropathy
- Glomerulonephritis
- Hydronephrosis is the enlargement of one or both of the kidneys caused by obstruction of the flow of urine.
- Interstitial nephritis
- Kidney stones (nephrolithiasis) are a relatively common and particularly painful disorder.
- Kidney tumors
- Lupus nephritis
- Minimal change disease
- In nephrotic syndrome, the glomerulus has been damaged so that a large amount of protein in the blood enters the urine. Other frequent features of the nephrotic syndrome include swelling, low serum albumin, and high cholesterol.
- Pyelonephritis is infection of the kidneys and is frequently caused by complication of a urinary tract infection.
- Renal failure
[edit] Kidney failure
Generally, humans can live normally with just one kidney, as one has more functioning renal tissue than is needed to survive. Only when the amount of functioning kidney tissue is greatly diminished will chronic kidney disease develop. Renal replacement therapy, in the form of dialysis or kidney transplantation, is indicated when the glomerular filtration rate has fallen very low or if the renal dysfunction leads to severe symptoms.
[edit] History
[edit] Human thought about kidneys
The Latin term renes is related to the English word "reins", a synonym for the kidneys in Shakespearean English (eg. Merry Wives of Windsor 3.5), which was also the time the King James Version was translated. Kidneys were once popularly regarded as the seat of the conscience and reflection[6][7], and a number of verses in the Bible (eg. Ps. 7:9, Rev. 2:23) state that God searches out and inspects the kidneys, or "reins", of humans. Similarly, the Talmud (Berakhoth 61.a) states that one of the two kidneys counsels what is good, and the other evil.
[edit] Animal kidneys as food
The kidneys of animals can be cooked and eaten by humans (along with other offal).
Kidneys are usually grilled or sautéed, but in more complex dishes they are stewed with a sauce that will improve their flavor. In many preparations kidneys are combined with pieces of meat or liver, like in mixed grill or in Meurav Yerushalmi. Among the most reputed kidney dishes, the British Steak and kidney pie, the Swedish Hökarpanna (pork and kidney stew), the French Rognons de veau sauce moutarde (veal kidneys in mustard sauce) and the Spanish "Riñones al Jerez" (kidneys stewed in sherry sauce), deserve special mention.[8]
[edit] See also
[edit] References
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Wikimedia Commons has media related to: Kidney |
- ^ Cotran, RS S.; Kumar, Vinay; Fausto, Nelson; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, MO: Elsevier Saunders. ISBN 0-7216-0187-1.
- ^ a b c d e Walter F., PhD. Boron (2004). Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. ISBN 1-4160-2328-3.
- ^ Bruce M. Carlson (2004). Human Embryology and Developmental Biology (3rd edition ed.). Saint Louis: Mosby. ISBN 0-323-03649-X.
- ^ Al-kahtani, M. A.; C. Zuleta, E. Caviedes-Vidal, and T. Garland, Jr. (2004). "Kidney mass and relative medullary thickness of rodents in relation to habitat, body size, and phylogeny". Physiological and Biochemical Zoology 77: 346-365. http://www.biology.ucr.edu/people/faculty/Garland/Al-kahtaniEA2004.pdf.
- ^ Maton, Anthea; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1.
- ^ The Patient as Person: Explorations in Medical Ethics p. 60 by Paul Ramsey, Margaret Farley, Albert Jonsen, William F. May (2002)
- ^ History of Nephrology 2 p. 235 by International Association for the History of Nephrology Congress, Garabed Eknoyan, Spyros G. Marketos, Natale G. De Santo - 1997; Reprint of American Journal of Nephrology; v. 14, no. 4-6, 1994.
- ^ Rognons dans les recettes (French)
[edit] External links
- electron microscopic images of the kidney (Dr. Jastrow's EM-Atlas)
- European Renal Genome project kidney function tutorial
- Kidney Foundation of Canada kidney disease information
- National Kidney Foundation
- Kidney Foundation (Canada)
- BC Renal Agency - Official site for the province-wide network of renal care providers in British Columbia, Canada
- World Kidney Day website
- UNC Nephropathology
- American Society of Nephrology
- Renal Fellow Network: Structure & Function of Other Animals' Kidneys
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