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79-770: BOSC 23 is a human kidney cell line developed by Warren Pear in David Baltimore's lab that was derived from the 293T cell line. The main use of BOSC 23 is the production of recombinant retroviruses ; it stably expresses Moloney murine leukemia virus proteins and when transiently transfected with recombinant retroviral vector DNA, produces high titers of infectious retroviral particles. The cell line does not produce detectable replication-competent virus, an important safety feature. BOSC 23 carries neomycin / G418 resistance derived from its parental line 293T, and also hygromycin and mycophenolic acid (gpt) resistance. It should be maintained under gpt selection. This cell line

158-431: A hyperosmotic medulla and thus increase the body plasma volume: Urea recycling and the 'single effect.' Urea is usually excreted as a waste product from the kidneys. However, when plasma blood volume is low and ADH is released the aquaporins that are opened are also permeable to urea. This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water. Urea can then re-enter

237-499: A pathological diagnosis. A renal pathologist is a physician who has undergone general training in anatomic pathology and additional specially training in the interpretation of renal biopsy specimens. Ideally, multiple core sections are obtained and evaluated for adequacy (presence of glomeruli) intraoperatively. A pathologist/pathology assistant divides the specimen(s) for submission for light microscopy, immunofluorescence microscopy and electron microscopy. The pathologist will examine

316-491: A portion of medulla called a renal pyramid . Between the renal pyramids are projections of cortex called renal columns . 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 . This becomes the ureter. At the hilum, the ureter and renal vein exit the kidney and the renal artery enters. Hilar fat and lymphatic tissue with lymph nodes surround these structures. The hilar fat

395-652: A tight hairpin configuration of the tubules, water and ion permeability in the descending limb of the loop, water impermeability in the ascending loop, and active ion transport out of most of the ascending limb. In addition, passive countercurrent exchange by the vessels carrying the blood supply to the nephron is essential for enabling this function. The kidney participates in whole-body homeostasis , regulating acid–base balance , electrolyte concentrations, extracellular fluid volume , and blood pressure . The kidney accomplishes these homeostatic functions both independently and in concert with other organs, particularly those of

474-456: Is homologous with the vas deferens of amniotes. However, the situation is not always so simple; in cartilaginous fish and some amphibians, there is also a shorter duct, similar to the amniote ureter, which drains the posterior (metanephric) parts of the kidney, and joins with the archinephric duct at the bladder or cloaca . Indeed, in many cartilaginous fish, the anterior portion of the kidney may degenerate or cease to function altogether in

553-399: Is urination itself, renal clearance is also conventionally called excretion (for example, in the set term fractional excretion of sodium ). The blood is filtered by nephrons , the functional units of the kidney. Each nephron begins in a renal corpuscle , which is composed of a glomerulus enclosed in a Bowman's capsule . Cells, proteins, and other large molecules are filtered out of

632-489: Is a model for cancer research, with emphasis on the lack of activated Src protein. Kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys , usually without signs of external lobulation. They are located on the left and right in the retroperitoneal space , and in adult humans are about 12 centimetres ( 4 + 1 ⁄ 2 inches) in length. They receive blood from

711-408: Is an adjective meaning “relating to the kidneys”, and its roots are French or late Latin. Whereas according to some opinions, "renal" should be replaced with "kidney" in scientific writings such as "kidney artery", other experts have advocated preserving the use of "renal" as appropriate including in "renal artery". In humans, the kidneys are located high in the abdominal cavity , one on each side of

790-562: Is contiguous with a fat-filled cavity called the renal sinus . The renal sinus collectively contains the renal pelvis and calyces and separates these structures from the renal medullary tissue. The kidneys possess no overtly moving structures. The kidneys receive blood from the renal arteries , left and right, which branch directly from the abdominal aorta . The kidneys receive approximately 20–25% of cardiac output in adult human. Each renal artery branches into segmental arteries, dividing further into interlobar arteries , which penetrate

869-402: Is divided into three or more distinct lobes. The lobes consists of several small, irregularly arranged, lobules, each centred on a branch of the ureter. Birds have small glomeruli, but about twice as many nephrons as similarly sized mammals. The human kidney is fairly typical of that of mammals . Distinctive features of the mammalian kidney, in comparison with that of other vertebrates, include

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948-497: Is frequently used to cure renal cell carcinoma . Renal physiology is the study of kidney function . Nephrology is the medical specialty which addresses diseases of kidney function : these include CKD, nephritic and nephrotic syndromes , acute kidney injury , and pyelonephritis . Urology addresses diseases of kidney (and urinary tract) anatomy : these include cancer , renal cysts , kidney stones and ureteral stones , and urinary tract obstruction . The word “ renal ”

1027-526: Is indicated when the glomerular filtration rate has fallen very low or if the renal dysfunction leads to severe symptoms. Dialysis is a treatment that substitutes for the function of normal kidneys. Dialysis may be instituted when approximately 85%–90% of kidney function is lost, as indicated by a glomerular filtration rate (GFR) of less than 15. Dialysis removes metabolic waste products as well as excess water and sodium (thereby contributing to regulating blood pressure); and maintains many chemical levels within

1106-529: Is indirect. For example, bicarbonate (HCO 3 ) does not have a transporter, so its reabsorption involves a series of reactions in the tubule lumen and tubular epithelium. It begins with the active secretion of a hydrogen ion (H ) into the tubule fluid via a Na/H exchanger : Some key regulatory hormones for re-absorption include: Both hormones exert their effects principally on the collecting ducts . Tubular secretion occurs simultaneously during re-absorption of filtrate. Substances, generally produced by body or

1185-417: Is often ascertained by estimating the rate of filtration, called the glomerular filtration rate (GFR). The kidney's ability to perform many of its functions depends on the three fundamental functions of filtration , reabsorption , and secretion , whose sum is called renal clearance or renal excretion. That is: Although the strictest sense of the word excretion with respect to the urinary system

1264-463: Is secreted by means of sodium-potassium pump, hydrogen ion is secreted by means of active transport and co-transport, i.e. anti-porter, and ammonia diffuses into renal tubule. The kidneys secrete a variety of hormones , including erythropoietin , calcitriol , and renin . Erythropoietin is released in response to hypoxia (low levels of oxygen at tissue level) in the renal circulation. It stimulates erythropoiesis (production of red blood cells) in

1343-428: Is sensed in the corresponding dermatome . Thus, pain in the flank region may be referred from corresponding kidney. Nephrons , the urine-producing functional structures of the kidney, span the cortex and medulla. The initial filtering portion of a nephron is the renal corpuscle , which is located in the cortex. This is followed by a renal tubule that passes from the cortex deep into the medullary pyramids. Part of

1422-469: Is slightly lower. The right kidney sits just below the diaphragm and posterior to the liver . The left kidney sits below the diaphragm and posterior to the spleen . On top of each kidney is an adrenal gland . The upper parts of the kidneys are partially protected by the 11th and 12th ribs . Each kidney, with its adrenal gland is surrounded by two layers of fat: the perirenal fat present between renal fascia and renal capsule and pararenal fat superior to

1501-447: Is studied at the level of the nephron , the smallest functional unit of the kidney. Each nephron begins with a filtration component that filters the blood entering the kidney. This filtrate then flows along the length of the nephron, which is a tubular structure lined by a single layer of specialized cells and surrounded by capillaries . The major functions of these lining cells are the reabsorption of water and small molecules from

1580-419: Is the peritoneum , while the posterior (rear) surface is the transversalis fascia . The superior pole of the right kidney is adjacent to the liver. For the left kidney, it is next to the spleen . Both, therefore, move down upon inhalation. A Danish study measured the median renal length to be 11.2 cm ( 4 + 7 ⁄ 16  in) on the left side and 10.9 cm ( 4 + 5 ⁄ 16  in) on

1659-413: Is the process by which solutes and water are removed from the tubular fluid and transported into the blood. It is called reabsorption (and not absorption ) both because these substances have already been absorbed once (particularly in the intestines ) and because the body is reclaiming them from a postglomerular fluid stream that is well on its way to becoming urine (that is, they will soon be lost to

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1738-450: Is the production of urine . These include the nitrogenous wastes urea , from protein catabolism , and uric acid , from nucleic acid metabolism. The ability of mammals and some birds to concentrate wastes into a volume of urine much smaller than the volume of blood from which the wastes were extracted is dependent on an elaborate countercurrent multiplication mechanism. This requires several independent nephron characteristics to operate:

1817-485: Is the specialty under Surgery that deals with kidney structure abnormalities such as kidney cancer and cysts and problems with urinary tract . Nephrologists are internists , and urologists are surgeons , whereas both are often called "kidney doctors". There are overlapping areas that both nephrologists and urologists can provide care such as kidney stones and kidney related infections . There are many causes of kidney disease . Some causes are acquired over

1896-492: Is the transport of molecules from this ultrafiltrate and into the peritubular capillary network that surrounds the nephron tubules. It is accomplished via selective receptors on the luminal cell membrane. Water is 55% reabsorbed in the proximal tubule. Glucose at normal plasma levels is completely reabsorbed in the proximal tubule. The mechanism for this is the Na /glucose cotransporter. A plasma level of 350 mg/dL will fully saturate

1975-494: The bone marrow . Calcitriol , the activated form of vitamin D , promotes intestinal absorption of calcium and the renal reabsorption of phosphate . Renin is an enzyme which regulates angiotensin and aldosterone levels. The kidney is responsible for maintaining a balance of the following substances: 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

2054-409: The bone marrow . Calcitriol , the activated form of vitamin D , promotes intestinal absorption of calcium and the renal reabsorption of phosphate . Renin is an enzyme which regulates angiotensin and aldosterone levels. Although the kidney cannot directly sense blood, long-term regulation of blood pressure predominantly depends upon the kidney. This primarily occurs through maintenance of

2133-445: The endocrine system . Various endocrine hormones coordinate these endocrine functions; these include renin , angiotensin II , aldosterone , antidiuretic hormone , and atrial natriuretic peptide , among others. Filtration, which takes place at the renal corpuscle , is the process by which cells and large proteins are retained while materials of smaller molecular weights are filtered from

2212-458: The extracellular fluid compartment, the size of which depends on the plasma sodium concentration. Renin is the first in a series of important chemical messengers that make up the renin–angiotensin system . Changes in renin ultimately alter the output of this system, principally the hormones angiotensin II and aldosterone . Each hormone acts via multiple mechanisms, but both increase the kidney's absorption of sodium chloride , thereby expanding

2291-418: The posterior pituitary gland . An increase in osmolality causes the gland to secrete antidiuretic hormone (ADH), resulting in water reabsorption by the kidney and an increase in urine concentration. The two factors work together to return the plasma osmolality to its normal levels. Various calculations and methods are used to try to measure kidney function. Renal clearance is the volume of plasma from which

2370-451: The renal fascia . The human kidney is a bean-shaped structure with a convex and a concave border. A recessed area on the concave border is the renal hilum , where the renal artery enters the kidney and the renal vein and ureter leave. The kidney is surrounded by tough fibrous tissue, the renal capsule , which is itself surrounded by perirenal fat , renal fascia , and pararenal fat . The anterior (front) surface of these tissues

2449-501: The renin–angiotensin system . Changes in renin ultimately alter the output of this system, principally the hormones angiotensin II and aldosterone . Each hormone acts via multiple mechanisms, but both increase the kidney's absorption of sodium chloride , thereby expanding the extracellular fluid compartment and raising blood pressure. When renin levels are elevated, the concentrations of angiotensin II and aldosterone increase, leading to increased sodium chloride reabsorption, expansion of

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2528-406: The spine , and lie in a retroperitoneal position at a slightly oblique angle. The asymmetry within the abdominal cavity, caused by the position of the liver , typically results in the right kidney being slightly lower and smaller than the left, and being placed slightly more to the middle than the left kidney. The left kidney is approximately at the vertebral level T12 to L3 , and the right

2607-504: The urinary bladder harbour specialized parasites , monogeneans of the family Polystomatidae. The kidneys of reptiles consist of a number of lobules arranged in a broadly linear pattern. Each lobule contains a single branch of the ureter in its centre, into which the collecting ducts empty. Reptiles have relatively few nephrons compared with other amniotes of a similar size, possibly because of their lower metabolic rate . Birds have relatively large, elongated kidneys, each of which

2686-480: The acid-base balance: to reabsorb and regenerate bicarbonate from urine, and to excrete hydrogen ions and fixed acids (anions of acids) into urine. The kidneys help maintain the water and salt level of the body. Any significant rise in plasma osmolality is detected by the hypothalamus , which communicates directly with the posterior pituitary gland . An increase in osmolality causes the gland to secrete antidiuretic hormone (ADH), resulting in water reabsorption by

2765-553: The action of aldosterone , antidiuretic hormone (ADH, or vasopressin), atrial natriuretic peptide (ANP), and other hormones. Abnormal ranges of the fractional excretion of sodium can imply acute tubular necrosis or glomerular dysfunction. Two organ systems, the kidneys and lungs, maintain acid-base homeostasis, which is the maintenance of pH around a relatively stable value. The lungs contribute to acid-base homeostasis by regulating carbon dioxide (CO 2 ) concentration. The kidneys have two very important roles in maintaining

2844-524: The adult. In the most primitive vertebrates, the hagfish and lampreys , the kidney is unusually simple: it consists of a row of nephrons, each emptying directly into the archinephric duct. Invertebrates may possess excretory organs that are sometimes referred to as "kidneys", but, even in Amphioxus , these are never homologous with the kidneys of vertebrates, and are more accurately referred to by other names, such as nephridia . In amphibians , kidneys and

2923-413: The aquaporins of the collecting duct be opened by ADH. Although the kidney cannot directly sense blood, long-term regulation of blood pressure predominantly depends upon the kidney. This primarily occurs through maintenance of the extracellular fluid compartment, the size of which depends on the plasma sodium concentration. Renin is the first in a series of important chemical messengers that make up

3002-461: The assessment of renal disease. The role of the renal biopsy is to diagnose renal disease in which the etiology is not clear based upon noninvasive means (clinical history, past medical history, medication history, physical exam, laboratory studies, imaging studies). In general, a renal pathologist will perform a detailed morphological evaluation and integrate the morphologic findings with the clinical history and laboratory data, ultimately arriving at

3081-495: The basis of a detailed medical history , and physical examination . The medical history takes into account present and past symptoms, especially those of kidney disease; recent infections; exposure to substances toxic to the kidney; and family history of kidney disease. Kidney function is tested by using blood tests and urine tests . The most common blood tests are creatinine , urea and electrolytes . Urine tests such as urinalysis can evaluate for pH, protein, glucose, and

3160-484: The blood and move it to the filtrate which helps to increase the pH of the blood. On the basal side of the cell there is a HCO 3 /Cl exchanger and a Cl/K co-transporter (facilitated diffusion). When the reaction is pushed to the left it also increases the HCO 3 concentration in the cell and HCO 3 is then able to move out into the blood which additionally raises the pH. The intercalated B cell responds very similarly, however,

3239-425: The blood moves through a small network of small veins ( 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 veins which exit the kidney. The kidney and nervous system communicate via the renal plexus , whose fibers course along

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3318-407: The blood to make an ultrafiltrate that eventually becomes urine. The adult human kidney generates approximately 180 liters of filtrate a day, most of which is reabsorbed. The normal range for a twenty four hour urine volume collection is 800 to 2,000 milliliters per day. The process is also known as hydrostatic filtration due to the hydrostatic pressure exerted on the capillary walls. Reabsorption

3397-493: The blood volume that enters the kidneys is filtered. Examples of substances reabsorbed are solute-free water , sodium , bicarbonate , glucose , and amino acids . Examples of substances secreted are hydrogen , ammonium , potassium and uric acid . The nephron is the structural and functional unit of the kidney. 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

3476-426: The body is experiencing acidic conditions. Under acidic conditions, the high concentration of CO 2 in the blood creates a gradient for CO 2 to move into the cell and push the reaction HCO 3 + H ↔ H 2 CO 3 ↔ CO 2 + H 2 O to the left. On the luminal side of the cell there is a H pump and a H/K exchanger. These pumps move H against their gradient and therefore require ATP. These cells will remove H from

3555-425: 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. Acids are divided into "volatile acids" and "nonvolatile acids". See also titratable acid . The major homeostatic control point for maintaining this stable balance is renal excretion. The kidney is directed to excrete or retain sodium via

3634-554: The body pH to a value of 7.4 by controlling the respiratory rate. When the body is experiencing acidic conditions, it will increase the respiratory rate which in turn drives off CO 2 and decreases the H concentration, therefore increasing the pH. In basic conditions, the respiratory rate will slow down so that the body holds onto more CO 2 and increases the H concentration and decreases the pH. The kidneys have two cells that help to maintain acid-base homeostasis: intercalated A and B cells. The intercalated A cells are stimulated when

3713-412: The body's acid–base balance are the kidneys and lungs. Acid–base homeostasis is the maintenance of pH around a value of 7.4. The lungs are the part of respiratory system which helps to maintain acid–base homeostasis by regulating carbon dioxide (CO 2 ) concentration in the blood. The respiratory system is the first line of defense when the body experiences and acid–base problem. It attempts to return

3792-437: The body. Life expectancy is 5–10 years for those on dialysis; some live up to 30 years. Dialysis can occur via the blood (through a catheter or arteriovenous fistula ), or through the peritoneum ( peritoneal dialysis ) Dialysis is typically administered three times a week for several hours at free-standing dialysis centers, allowing recipients to lead an otherwise essentially normal life. Many renal diseases are diagnosed on

3871-504: The by-products of cell metabolism that can become toxic in high concentration, and some drugs (if taken). These all are secreted into the lumen of renal tubule. Tubular secretion can be either active or passive or co-transport. Substances mainly secreted into renal tubule are; H+, K+, NH3, urea, Creatinine, histamine and drugs like penicillin. Tubular secretion occurs at Proximal Convoluted Tubule (PCT) and Distal Convoluted Tubule (D.C.T); for example, at proximal convoluted tubule, potassium

3950-544: The course of life, such as diabetic nephropathy whereas others are congenital , such as polycystic kidney disease . 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) . For example, surgical removal of

4029-504: The extracellular fluid compartment and raising blood pressure. When renin levels are elevated, the concentrations of angiotensin II and aldosterone increase, leading to increased sodium chloride reabsorption, expansion of the extracellular fluid compartment, and an increase in blood pressure. Conversely, when renin levels are low, angiotensin II and aldosterone levels decrease, contracting the extracellular fluid compartment, and decreasing blood pressure. The two organ systems that help regulate

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4108-468: The extracellular fluid compartment, and an increase in blood pressure. Conversely, when renin levels are low, angiotensin II and aldosterone levels decrease, contracting the extracellular fluid compartment, and decreasing blood pressure. The kidney in humans is capable of producing glucose from lactate , glycerol and glutamine . The kidney is responsible for about half of the total gluconeogenesis in fasting humans. The regulation of glucose production in

4187-406: The filtrate into the blood, and the secretion of wastes from the blood into the urine. Proper function of the kidney requires that it receives and adequately filters blood. This is performed at the microscopic level by many hundreds of thousands of filtration units called renal corpuscles , each of which is composed of a glomerulus and a Bowman's capsule . A global assessment of renal function

4266-440: The glomerulus by a process of ultrafiltration , leaving an ultrafiltrate that resembles plasma (except that the ultrafiltrate has negligible plasma proteins ) to enter Bowman's space. Filtration is driven by Starling forces . The ultrafiltrate is passed through, in turn, the proximal convoluted tubule , the loop of Henle , the distal convoluted tubule , and a series of collecting ducts to form urine . Tubular reabsorption

4345-425: The kidney and an increase in urine concentration. The two factors work together to return the plasma osmolality to its normal levels. ADH binds to principal cells in the collecting duct that translocate aquaporins to the membrane, allowing water to leave the normally impermeable membrane and be reabsorbed into the body by the vasa recta, thus increasing the plasma volume of the body. There are two systems that create

4424-427: The kidney is a nephrectomy , while a reduction in kidney function is called renal dysfunction . 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 does one develop chronic kidney disease . Renal replacement therapy , in the form of dialysis or kidney transplantation ,

4503-434: The kidney is achieved by action of insulin , catecholamines and other hormones. Renal gluconeogenesis takes place in the renal cortex . The renal medulla is incapable of producing glucose due to absence of necessary enzymes . A simple means of estimating renal function is to measure pH , blood urea nitrogen , creatinine , and basic electrolytes (including sodium , potassium , chloride , and bicarbonate ). As

4582-463: The kidney with podocin and nephrin expressed in glomeruli, Solute carrier family protein SLC22A8 expressed in proximal tubules, calbindin expressed in distal tubules and aquaporin 2 expressed in the collecting duct cells. The mammalian kidney develops from intermediate mesoderm . Kidney development , also called nephrogenesis , proceeds through a series of three successive developmental phases:

4661-426: The kidney, with only some 50 genes being highly specific for the kidney. Many of the corresponding kidney specific proteins are expressed in the cell membrane and function as transporter proteins. The highest expressed kidney specific protein is uromodulin , the most abundant protein in urine with functions that prevent calcification and growth of bacteria. Specific proteins are expressed in the different compartments of

4740-487: The management of kidney disease include chemical and microscopic examination of the urine ( urinalysis ), measurement of kidney function by calculating the estimated glomerular filtration rate (eGFR) using the serum creatinine ; and kidney biopsy and CT scan to evaluate for abnormal anatomy. Dialysis and kidney transplantation are used to treat kidney failure ; one (or both sequentially) of these are almost always used when renal function drops below 15%. Nephrectomy

4819-444: The membrane proteins are flipped from the intercalated A cells: the proton pumps are on the basal side and the HCO 3 /Cl exchanger and K/Cl co-transporter are on the luminal side. They function the same, but now release protons into the blood to decrease the pH. The kidneys help maintain the water and salt level of the body. Any significant rise in plasma osmolality is detected by the hypothalamus , which communicates directly with

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4898-462: The multilobed reniculate kidneys of pinnipeds and cetaceans . 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 and diet (e.g., carnivores have only long loops of Henle). Renal physiology Much of renal physiology

4977-439: The nephron and be excreted or recycled again depending on whether ADH is still present or not. The 'single effect' describes the fact that the ascending thick limb of the loop of Henle is not permeable to water but is permeable to sodium chloride . This allows for a countercurrent exchange system whereby the medulla becomes increasingly concentrated, but at the same time setting up an osmotic gradient for water to follow should

5056-438: The nephrons. For example, they convert a precursor of vitamin D to its active form, calcitriol ; and synthesize the hormones erythropoietin and renin . Chronic kidney disease (CKD) has been recognized as a leading public health problem worldwide. The global estimated prevalence of CKD is 13.4%, and patients with kidney failure needing renal replacement therapy are estimated between 5 and 7 million. Procedures used in

5135-402: The paired renal arteries ; blood exits into the paired renal veins . Each kidney is attached to a ureter , a tube that carries excreted urine to the bladder . The kidney participates in the control of the volume of various body fluids , fluid osmolality , acid-base balance , various electrolyte concentrations, and removal of toxins . Filtration occurs in the glomerulus : one-fifth of

5214-453: The patient's renal disease. In the majority of vertebrates, the mesonephros persists into the adult, albeit usually fused with the more advanced metanephros ; only in amniotes is the mesonephros restricted to the embryo. The kidneys of fish and amphibians are typically narrow, elongated organs, occupying a significant portion of the trunk. The collecting ducts from each cluster of nephrons usually drain into an archinephric duct , which

5293-533: The presence of blood. Microscopic analysis can also identify the presence of urinary casts and crystals. The glomerular filtration rate (GFR) can be directly measured ("measured GFR", or mGFR) but this rarely done in everyday practice. Instead, special equations are used to calculate GFR ("estimated GFR", or eGFR). Renal ultrasonography is essential in the diagnosis and management of kidney-related diseases. Other modalities, such as CT and MRI , should always be considered as supplementary imaging modalities in

5372-467: The presence of the renal pelvis and renal pyramids and a clearly distinguishable cortex and medulla. The latter feature is due to the presence of elongated loops of Henle ; these are much shorter in birds, and not truly present in other vertebrates (although the nephron often has a short intermediate segment between the convoluted tubules). It is only in mammals that the kidney takes on its classical "kidney" shape, although there are some exceptions, such as

5451-399: The pronephros, mesonephros, and metanephros. The metanephros are primordia of the permanent kidney. The kidneys excrete a variety of waste products produced by metabolism into the urine. The microscopic structural and functional unit of the kidney is the nephron . It processes the blood supplied to it via filtration, reabsorption, secretion and excretion; the consequence of those processes

5530-464: The renal arteries to reach each kidney. Input from the sympathetic nervous system triggers vasoconstriction in the kidney, thereby reducing renal blood flow . The kidney also receives input from the parasympathetic nervous system , by way of the renal branches of the vagus nerve ; the function of this is yet unclear. Sensory input from the kidney travels to the T10–11 levels of the spinal cord and

5609-440: 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. Blood drains from the kidneys, ultimately into the inferior vena cava . After filtration occurs,

5688-561: The renal cortex, a medullary ray is a collection of renal tubules that drain into a single collecting duct . Renal histology is the study of the microscopic structure of the kidney. The adult human kidney contains at least 26 distinct cell types , including epithelial, endothelial, stromal and smooth muscle cells. Distinct cell types include: In humans, about 20,000 protein coding genes are expressed in human cells and almost 70% of these genes are expressed in normal, adult kidneys. Just over 300 genes are more specifically expressed in

5767-412: The reverse of reabsorption: molecules are transported from the peritubular capillary through the interstitial fluid, then through the renal tubular cell and into the ultrafiltrate. The last step in the processing of the ultrafiltrate is excretion : the ultrafiltrate passes out of the nephron and travels through a tube called the collecting duct , which is part of the collecting duct system , and then to

5846-476: The right side in adults. Median renal volumes were 146 cm ( 8 + 15 ⁄ 16  cu in) on the left and 134 cm ( 8 + 3 ⁄ 16  cu in) on the right. The functional substance, or parenchyma , of the human kidney is divided into two major structures: the outer renal cortex and the inner renal medulla . Grossly, these structures take the shape of eight to 18 cone-shaped renal lobes , each containing renal cortex surrounding

5925-471: The specimen using light microscopy with multiple staining techniques (hematoxylin and eosin/H&E, PAS, trichrome, silver stain) on multiple level sections. Multiple immunofluorescence stains are performed to evaluate for antibody, protein and complement deposition. Finally, ultra-structural examination is performed with electron microscopy and may reveal the presence of electron-dense deposits or other characteristic abnormalities that may suggest an etiology for

6004-598: The substance is completely cleared from the blood per unit time. The filtration fraction is the amount of plasma that is actually filtered through the kidney. This can be defined using the equation. The kidney is a very complex organ and mathematical modelling has been used to better understand kidney function at several scales, including fluid uptake and secretion. Nephrology is the subspeciality under Internal Medicine that deals with kidney function and disease states related to renal malfunction and their management including dialysis and kidney transplantation . Urology

6083-399: The transporters and glucose will be lost in the urine. A plasma glucose level of approximately 160 is sufficient to allow glucosuria, which is an important clinical clue to diabetes mellitus. Amino acids are reabsorbed by sodium dependent transporters in the proximal tubule. Hartnup disease is a deficiency of the tryptophan amino acid transporter, which results in pellagra . Secretion is

6162-427: The ureters where it is renamed urine . In addition to transporting the ultrafiltrate, the collecting duct also takes part in reabsorption. The kidneys secrete a variety of hormones , including erythropoietin , calcitriol , and renin . Erythropoietin is released in response to hypoxia (low levels of oxygen at tissue level) in the renal circulation. It stimulates erythropoiesis (production of red blood cells) in

6241-458: The urine unless they are reclaimed). Reabsorption is a two-step process beginning with the active or passive extraction of substances from the tubule fluid into the renal interstitium (the connective tissue that surrounds the nephrons), and then the transport of these substances from the interstitium into the bloodstream. These transport processes are driven by Starling forces , diffusion , and active transport . In some cases, reabsorption

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