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Extraglomerular Mesangial Cell
Extraglomerular mesangial cells (also known as Lacis cells, Polkissen cells, or Goormaghtigh cells) are light-staining pericytes in the kidney found outside the glomerulus, near the vascular pole. They resemble smooth muscle cells and play a role in renal autoregulation of blood flow to the kidney and regulation of systemic blood pressure through the renin–angiotensin system. Extraglomerular mesangial cells are part of the juxtaglomerular apparatus, along with the macula densa cells of the distal convoluted tubule and the juxtaglomerular cells of the afferent arteriole. The specific function of extraglomerular mesangial cells is not well understood, although it has been associated with the secretion of erythropoietin and secretion of renin. They are distinguished from intraglomerular mesangial cells, which are situated between the basement membrane and the epithelial cells within the glomerulus ''Glomerulus'' () is a common term used in anatomy to describe globular struct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pericytes
Pericytes (previously known as Rouget cells) are multi-functional mural cells of the microcirculation that wrap around the endothelial cells that line the capillaries throughout the body. Pericytes are embedded in the basement membrane of blood capillaries, where they communicate with endothelial cells by means of both direct physical contact and paracrine signaling. The morphology, distribution, density and molecular fingerprints of pericytes vary between organs and vascular beds. Pericytes help to maintain homeostatic and hemostatic functions in the brain, one of the organs with higher pericyte coverage, and also sustain the blood–brain barrier. These cells are also a key component of the neurovascular unit, which includes endothelial cells, astrocytes, and neurons. Pericytes have been postulated to regulate capillary blood flow and the clearance and phagocytosis of cellular debris ''in vitro.'' Pericytes stabilize and monitor the maturation of endothelial cells by means of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Juxtaglomerular Cells
Juxtaglomerular cells (JG cells), also known as juxtaglomerular granular cells are cells in the kidney that synthesize, store, and secrete the enzyme renin. They are specialized smooth muscle cells mainly in the walls of the afferent arterioles (and some in the efferent arterioles) that deliver blood to the glomerulus. In synthesizing renin, they play a critical role in the renin–angiotensin system and thus in autoregulation of the kidney. Juxtaglomerular cells secrete renin in response to a drop in pressure detected by stretch receptors in the vascular walls, or when stimulated by macula densa cells. Macula densa cells are located in the distal convoluted tubule, and stimulate juxtaglomerular cells to release renin when they detect a drop in chloride concentration in tubular fluid. Together, juxtaglomerular cells, extraglomerular mesangial cells and macula densa cells comprise the juxtaglomerular apparatus. In appropriately stained tissue sections, juxtaglomerular cells ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesangium
The glomerulus (plural glomeruli) is a network of small blood vessels (capillaries) known as a ''tuft'', located at the beginning of a nephron in the kidney. Each of the two kidneys contains about one million nephrons. The tuft is structurally supported by the mesangium (the space between the blood vessels), composed of intraglomerular mesangial cells. The blood is filtered across the capillary walls of this tuft through the glomerular filtration barrier, which yields its filtrate of water and soluble substances to a cup-like sac known as Bowman's capsule. The filtrate then enters the renal tubule of the nephron. The glomerulus receives its blood supply from an afferent arteriole of the renal arterial circulation. Unlike most capillary beds, the glomerular capillaries exit into efferent arterioles rather than venules. The resistance of the efferent arterioles causes sufficient hydrostatic pressure within the glomerulus to provide the force for ultrafiltration. The glomerulus a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glomerulus
''Glomerulus'' () is a common term used in anatomy to describe globular structures of entwined vessels, fibers, or neurons. ''Glomerulus'' is the diminutive of the Latin ''glomus'', meaning "ball of yarn". ''Glomerulus'' may refer to: * the filtering unit of the kidney; see Glomerulus (kidney). * a structure in the olfactory bulb; see Glomerulus (olfaction). * the contact between specific cells in the cerebellum; see Glomerulus (cerebellum) The cerebellar glomerulus is a small, intertwined mass of nerve fiber terminals in the granular layer of the cerebellar cortex. It consists of post-synaptic granule cell dendrites and pre-synaptic Golgi cell axon terminals surrounding the pre- .... See also * Glomerulation, a hemorrhage of the bladder {{SIA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intraglomerular Mesangial Cells
Intraglomerular mesangial cells are located among the glomerular capillaries within a renal corpuscle of a kidney. Characteristics Mesangial cells are macrophages and resemble pericytes. They typically cover 30% of glomerular capillaries. They are both vimentin and desmin positive. Function There are five known functions of intraglomerular mesangial cells: structural support of glomerular capillaries, regulation of the glomerular filtration rate, mesangial matrix formation, phagocytosis, and monitoring of capillary lumen glucose concentration. Intraglomerular mesangial cells have contractile activity. The initiation of contraction of mesangial cells is similar to that of smooth muscle. Contraction of mesangial cells is coupled with contraction of the basement membrane of the endothelium of glomerular capillaries. This causes a decrease in surface area of the basement membrane and thus a decreased glomerular filtration rate. Intraglomerular mesangial cells synthesize and sec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Renin
Renin (etymology and pronunciation), also known as an angiotensinogenase, is an aspartic protease protein and enzyme secreted by the kidneys that participates in the body's renin–angiotensin–aldosterone system (RAAS)—also known as the renin–angiotensin–aldosterone axis—that increases the volume of extracellular fluid ( blood plasma, lymph and interstitial fluid) and causes arterial vasoconstriction. Thus, it increases the body's mean arterial blood pressure. Renin is not commonly referred to as a hormone, albeit it having a receptor, the (pro)renin receptor, also known as the renin receptor and prorenin receptor (see also below), as well as enzymatic activity with which it hydrolyzes angiotensinogen to angiotensin I. Biochemistry and physiology Structure The primary structure of renin precursor consists of 406 amino acids with a pre- and a pro-segment carrying 20 and 46 amino acids, respectively. Mature renin contains 340 amino acids and has a mass of 3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erythropoietin
Erythropoietin (; EPO), also known as erythropoetin, haematopoietin, or haemopoietin, is a glycoprotein cytokine secreted mainly by the kidneys in response to cellular hypoxia; it stimulates red blood cell production ( erythropoiesis) in the bone marrow. Low levels of EPO (around 10 mU/mL) are constantly secreted in sufficient quantities to compensate for normal red blood cell turnover. Common causes of cellular hypoxia resulting in elevated levels of EPO (up to 10 000 mU/mL) include any anemia, and hypoxemia due to chronic lung disease. Erythropoietin is produced by interstitial fibroblasts in the kidney in close association with the peritubular capillary and proximal convoluted tubule. It is also produced in perisinusoidal cells in the liver. Liver production predominates in the fetal and perinatal period; renal production predominates in adulthood. It is homologous with thrombopoietin. Exogenous erythropoietin, recombinant human erythropoietin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Afferent Arteriole
The afferent arterioles are a group of blood vessels that supply the nephrons in many excretory systems. They play an important role in the regulation of blood pressure as a part of the tubuloglomerular feedback mechanism. The afferent arterioles branch from the renal artery, which supplies blood to the kidneys. The afferent arterioles later diverge into the capillaries of the glomerulus. Regulation When renal blood flow is reduced (indicating hypotension) or there is a decrease in sodium or chloride ion concentration, the macula densa of the distal tubule releases prostaglandins (mainly PGI2 and PGE2) and nitric oxide, which cause the juxtaglomerular cells lining the afferent arterioles to release renin, activating the renin–angiotensin–aldosterone system, to increase blood pressure and increase reabsorption of sodium ions into the bloodstream via aldosterone. The macula densa cell can also increase the blood pressure of the afferent arterioles by decreasing the synthes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distal Convoluted Tubule
The distal convoluted tubule (DCT) is a portion of kidney nephron between the loop of Henle and the collecting tubule. Physiology It is partly responsible for the regulation of potassium, sodium, calcium, and pH. On its apical surface (lumen side), cells of the DCT have a thiazide-sensitive Na-Cl cotransporter and are permeable to Ca, via the TRPV5 channel. On the basolateral surface (peritubular capillary side) there is an ATP-dependent Na/K antiporter pump, a secondary active Na/Ca transporter, and an ATP dependent Ca transporter. The basolateral ATP dependent Na/K pump produces the gradient for Na to be absorbed from the apical surface via the Na/Cl symporter, and for Ca to be reclaimed into the blood by the Na/Ca basolateral antiporter. * It regulates pH by absorbing bicarbonate and secreting protons (H+) into the filtrate, or by absorbing protons and secreting bicarbonate into the filtrate. * Sodium and potassium levels are controlled by secreting K+ and absorbing Na+. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kidney
The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from 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 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 con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macula Densa
In the kidney, the macula densa is an area of closely packed specialized cells lining the wall of the distal tubule, at the point where the thick ascending limb of the Loop of Henle meets the distal convoluted tubule. The macula densa is the thickening where the distal tubule touches the glomerulus. The cells of the macula densa are sensitive to the concentration of sodium chloride in the distal convoluted tubule. A decrease in sodium chloride concentration initiates a signal from the macula densa that has two effects: (1) it decreases resistance to blood flow in the afferent arterioles, which raises glomerular hydrostatic pressure and helps return the glomerular filtration rate (GFR) toward normal, and (2) it increases renin release from the juxtaglomerular cells of the afferent and efferent arterioles, which are the major storage sites for renin. As such, an increase in sodium chloride concentration would result in vasoconstriction of afferent arterioles, and reduced par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Juxtaglomerular Apparatus
The juxtaglomerular apparatus (also known as the juxtaglomerular complex) is a structure in the kidney that regulates the function of each nephron, the functional units of the kidney. The juxtaglomerular apparatus is named because it is next to (juxta-) the glomerulus. The juxtaglomerular apparatus consists of three types of cells: # the macula densa, a part of the distal convoluted tubule of the same nephron # juxtaglomerular cells, (also known as granular cells) which secrete renin # extraglomerular mesangial cells Location The juxtaglomerular apparatus is part of the kidney nephron, next to the glomerulus. It is found between afferent arteriole and the distal convoluted tubule of the same nephron. This location is critical to its function in regulating renal blood flow and glomerular filtration rate. Function Juxtaglomerular cells Renin is produced by juxtaglomerular cells, also known as granular cells. These cells are similar to epithelium and are located in the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
