Glomerulus
Glomerulus.
Distribution of bloodvessels in cortex of kidney.
Latin	glomerulus renis
Gray's	subject #253 1221
Precursor	Metanephric blastema
MeSH	Kidney+Glomerulus
Dorlands/Elsevier	g_07/12394744

A glomerulus is a capillary tuft surrounded by Bowman's capsule in nephrons of the vertebrate kidney. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Gray's Anatomy the Respiratory apparatus ( Apparatus Respiratorius Respiratory system Respiratory apparatus Embryology (from Greek grc ἔμβρυον embryon, "unborn embryo" and grc -λογία -logia) is the study of the development The metanephric blastema (or metanephric mesenchyme, or metanephric mesoderm) is one of the two Embryological structures that give rise to the Kidney Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange The Bowman's capsule (other names capsula glomeruli glomerular capsule is a cup-like sac at the beginning of the tubular component of a Nephron in the mammalian A nephron (from Greek νεφρός (nephros meaning "kidney" is the basic structural and functional unit of the Kidney. The kidneys are complicated organs that have numerous biological roles It receives its blood supply from an afferent arteriole of the renal circulation. The afferent arterioles are a group of Blood vessels that supply the Nephrons in many excretory systems. The renal circulation receives around 20% of the Cardiac output. Unlike most other capillary beds, the glomerulus drains into an efferent arteriole rather than a venule. The efferent arterioles are blood vessels that are part of the urinary tract of Organisms. A venule is a small Blood vessel that allows deoxygenated Blood to return from the Capillary beds to the larger blood vessels called Veins The resistance of the arterioles results in high pressure in the glomerulus aiding the process of ultrafiltration where fluids and soluble materials in the blood are forced out of the capillaries and into Bowman's capsule. The Bowman's capsule (other names capsula glomeruli glomerular capsule is a cup-like sac at the beginning of the tubular component of a Nephron in the mammalian

A glomerulus and its surrounding Bowman's capsule constitute a renal corpuscle, the basic filtration unit of the kidney. The Bowman's capsule (other names capsula glomeruli glomerular capsule is a cup-like sac at the beginning of the tubular component of a Nephron in the mammalian In the Kidney, a renal corpuscle is the initial blood-filtering component of a Nephron. The rate at which blood is filtered through all of the glomeruli, and thus the measure of the overall renal function, is the glomerular filtration rate (GFR). Renal function, in Nephrology, is an indication of the state of the Kidney and its role in Renal physiology.

The first place where urine is formed in the kidney, filters fluid from the blood.

Afferent circulation

The afferent arteriole that supplies the glomerulus is a branch off of an interlobular artery in the cortex. The afferent arterioles are a group of Blood vessels that supply the Nephrons in many excretory systems. The first set of renal bloodvessels the interlobular arteries (or cortical radiate arteries, or cortical radial arteries) are given off at right angles from the

Layers

If a substance can pass through the endothelial cells, glomerular basement membrane, and podocytes, then it is known as ultrafiltrate, and it enters proximal tubule. The proximal tubule is the portion of the duct system of the Nephron leading from Bowman's capsule to the Loop of Henle. Otherwise, it returns through the efferent circulation, discussed below.

Endothelial cells

The endothelial cells of the glomerulus contain numerous pores (fenestrae) that, unlike those of other fenestrated capillaries, are not spanned by diaphragms. The endothelium is the thin layer of cells that line the interior surface of Blood vessels forming an interface between circulating Blood in the The cells have openings which are so large that nearly anything smaller than a red blood cell passes through that layer. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood

Because of this, the endothelial cells lining the glomerulus are not usually considered part of the renal filtration barrier.

Glomerular basement membrane

The glomerular endothelium sits on a very thick (250-350nm) glomerular basement membrane. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a The glomerular basement membrane is the Basal laminal portion of the Glomerulus which performs the actual filtration though the filtration slits between the Podocytes It is not only uncharacteristically thick compared to most other basement membranes (40-50 nm), but it is also rich in negatively charged glycosaminoglycans such as heparan sulfate. The basement membrane is a structure that supports overlying Epithelial or Endothelial cells. Glycosaminoglycans (GAGs or mucopolysaccharides are long unbranched Polysaccharides consisting of a repeating Disaccharide unit Heparan sulfate (HS is a linear Polysaccharide found in all animal tissues

The negatively-charged basement membrane repels negatively-charged proteins from the blood, helping to prevent their passage into Bowman's space.

Podocytes

Podocytes line the other side of the glomerular basement membrane and form part of the lining of Bowman's space. Podocytes (or visceral epithelial cells) are cells of the visceral Epithelium in the Kidneys and form a crucial component of the glomerular Podocytes form a tight interdigitating network of foot processes (pedicels) that control the filtration of proteins from the capillary lumen into Bowman's space.

The space between adjacent podocyte foot processes is spanned by a slit diaphragm formed by several proteins including podocin and nephrin. Foot processes of Podocytes interdigitate with one another forming filtration slits (or slit pores) that in contrast to those in the Glomerular Endothelium Podocin is a protein which lines the Podocytes and assists in maintaining the barrier at the Glomerular basement membrane. Nephrin is a Protein necessary for the proper functioning of the renal filtration barrier In addition, foot processes have a negatively-charged coat (glycocalyx) that limits the filtration of negatively-charged molecules, such as serum albumin. Glycocalyx is a general term referring to extracellular Polymeric material produced by some Bacteria, Epithelia and other cells Serum albumin, often referred to simply as albumin, is the most abundant Plasma protein in humans and other Mammals Albumin is essential for maintaining

The podocytes are sometimes considered the "visceral layer of Bowman's capsule", rather than part of the glomerulus. The Bowman's capsule (other names capsula glomeruli glomerular capsule is a cup-like sac at the beginning of the tubular component of a Nephron in the mammalian

Intraglomerular mesangial cell

Intraglomerular mesangial cells are found in the interstitium between endothelial cells of the glomerulus. Intraglomerular mesangial cells are specialized Pericytes located among the glomerular Capillaries within a Renal corpuscle of a Kidney They are not part of the filtration barrier but are specialized pericytes that participate indirectly in filtration. A pericyte, also known as Rouget cell or Mural cell, is a mesenchymal -like cell associated with the walls of small Blood vessels.

Selectivity

See also: Table of permselectivity for different substances

The structures of the layers determine their permeability-selectivity permselectivity. This is a table of Permselectivity for different substances in the Glomerulus of the Kidney in Renal filtration. Vascular permeability characterizes the capacity of a blood vessel wall to pass through small molecules (ions water nutrients or even whole cells ( Lymphocytes on their For instance, small ions such as sodium and potassium pass freely, while larger proteins, such as hemoglobin and albumin have practically no permeability at all. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Albumin (Latin albus white refers generally to any Protein with water Solubility, which is moderately soluble in concentrated salt solutions and experiences

Efferent circulation

Blood is carried out of the glomerulus by an efferent arteriole instead of a venule, as is observed in most other capillary systems. The efferent arterioles are blood vessels that are part of the urinary tract of Organisms. The efferent arterioles are blood vessels that are part of the urinary tract of Organisms. A venule is a small Blood vessel that allows deoxygenated Blood to return from the Capillary beds to the larger blood vessels called Veins This provides tighter control over the bloodflow through the glomerulus, since arterioles can be dilated and constricted more readily than venules, owing to arterioles' larger smooth muscle layer (tunica media). Smooth muscle is a type of non- Striated muscle, found within the Tunica media layer of large and small Arteries and Veins, the bladder The tunica media (or just media) ( middle coat) is the middle layer of an Artery or Vein.

Efferent arterioles of juxtamedullary nephrons (ie, the 15% of nephrons closest to the medulla) send straight capillary branches that deliver isotonic blood to the renal medulla. A juxtamedullary nephron is a type of Nephron. The "medullary" is referring to the Renal medulla, while the "juxta" refers to the relative position Along with the loop of Henle, these vasa recta play a crucial role in the establishment of the nephron's countercurrent exchange system. For the intestinal structure see Vasa recta (intestines In the blood supply of the kidney, the vasa recta renis (or straight arteries Countercurrent exchange is a mechanism used to transfer some property of a Fluid from one flowing current of fluid to another across a Semipermeable membrane or thermally-conductive

The efferent arteriole, into which the glomerulus delivers blood, empties into an interlobular vein. The efferent arterioles are blood vessels that are part of the urinary tract of Organisms. The venae stellatae join to form the interlobular veins, which pass inward between the Rays, receive branches from the Plexuses around the Convoluted

Juxtaglomerular cells

The walls of the afferent arteriole contain specialized smooth muscle cells that synthesize renin. Smooth muscle is a type of non- Striated muscle, found within the Tunica media layer of large and small Arteries and Veins, the bladder Renin (pronounced "Ree-nin" or "Rē-nin" (ˈriːnɨn also known as Angiotensinogenase, is a circulating Enzyme that participates in the body's These juxtaglomerular cells play a major role in the renin-angiotensin system, which helps regulate blood volume and pressure. In the Kidney, the juxtaglomerular cells ( JG cells, also known as granular cells) are cells that synthesize store and secrete the enzyme Renin The renin-angiotensin system (RAS or the renin-angiotensin-aldosterone system (RAAS is a hormone system that regulates Blood pressure and water ( fluid Blood volume is the Volume of Blood (both Red blood cells and plasma) in a person's Circulatory system. Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories

Additional images

1 Glomerulus, 2 proximal tubule, 3 distal tubule	Glomerulus. The proximal tubule is the portion of the duct system of the Nephron leading from Bowman's capsule to the Loop of Henle. The distal convoluted tubule ( DCT) is a portion of Kidney Nephron between the Loop of Henle and the Collecting duct system.	Section of cortex of human kidney.	Mouse glomerulus in the Scanning Electron Microscope ("SEM"), magnification 1,000x
Mouse glomerulus in the SEM, magnification 5,000x	Mouse glomerulus in the SEM with one capillary broken, magnification 10,000x	View on the inside of broken capillary with fenestrae visible, magnification 100,000x

External links

• Image and article at FGCU
• Histology at KUMC epithel-epith02 "Kidney (Glomerulus)"
• Organology at UC Davis Urinary/mammal/cortex1/cortex1 - "Mammal, kidney cortex (LM, Medium)"
• Histology at BU 16010loa
• UNC Nephropathology