| Podocyte | |
|---|---|
 |
|
| Glomerulus. (Diagram in French, but "Membrane basale glomerulaire et ses podocytes" labeled near center. The glomerular basement membrane is the Basal laminal portion of the Glomerulus which performs the actual filtration though the filtration slits between the Podocytes Podocytes (or visceral epithelial cells) are cells of the visceral Epithelium in the Kidneys and form a crucial component of the glomerular ) | |
| Dorlands/Elsevier | p_26/12652756 |
Podocytes (or visceral epithelial cells[1]) are cells of the visceral epithelium in the kidneys and form a crucial component of the glomerular filtration barrier, contributing size selectivity and maintaining a massive filtration surface. Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The kidneys are complicated organs that have numerous biological roles A glomerulus is a Capillary tuft surrounded by Bowman's capsule in Nephrons of the vertebrate Kidney.
Contents |
Function
Adjacent podocytes interdigitate to cover the basal lamina which is intimately associated with the glomerular capillaries, but the podocytes leave gaps or thin filtration slits. A glomerulus is a Capillary tuft surrounded by Bowman's capsule in Nephrons of the vertebrate Kidney. Foot processes of Podocytes interdigitate with one another forming filtration slits (or slit pores) that in contrast to those in the Glomerular Endothelium
The slits are covered by slit diaphragms which are composed of a number of cell-surface proteins including nephrin, podocalyxin, and P-cadherin, which ensure that large macromolecules such as serum albumin and gamma globulin remain in the bloodstream. Nephrin is a Protein necessary for the proper functioning of the renal filtration barrier Podocalyxin, a Sialoglycoprotein, is thought to be the major constituent of the Glycocalyx of Podocytes. Cadherins are a class of type-1 Transmembrane proteins They play important roles in Cell adhesion, ensuring that cells within tissues are bound together The term macromolecule by definition implies "large Molecule " Serum albumin, often referred to simply as albumin, is the most abundant Plasma protein in humans and other Mammals Albumin is essential for maintaining Gamma globulins, or Ig's are a class of Proteins in the blood identified by their position after Serum protein electrophoresis.
Small molecules such as water, glucose, and ionic salts are able to pass through the slit diaphragms and form an ultrafiltrate[2] which is further processed by the nephron to produce urine. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge A nephron (from Greek νεφρός (nephros meaning "kidney" is the basic structural and functional unit of the Kidney. Urine is a liquid waste product of the body secreted by the Kidneys by a process of filtration from Blood and Excreted through the Urethra.
Podocytes are also involved in regulation of glomerular filtration rate (GFR). When podocytes contract, they cause closure of filtration slits. This decreases the surface area available for filtration to occur. Thus, decreasing the GFR.
Structure features
Structural features of podocytes indicate a high rate of vesicular traffic in these cells. Many coated vesicles and coated pits can be seen along the basolateral domain of the podocytes. A vesicle is a small bubble of liquid within a cell A more formal definition in Cell biology, would be that a vesicle is a relatively small intracellular membrane-enclosed
In their cell bodies, podocytes possess a well-developed endoplasmic reticulum and a large Golgi apparatus, indicative of a high capacity for protein synthesis and post-translational modifications. The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle The Golgi apparatus (also called the Protein synthesis is the creation of proteins using DNA and' RNA'. Posttranslational modification (PTM is the chemical modification of a Protein after its translation.
There is also growing evidence of a large number of multivesicular bodies and other lysosomal components seen in these cells, indicating a high endocytic activity. Lysosomes are Organelles that contain Digestive enzymes (acid Hydrolases. Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane.
"Pedicels" (or "foot processes") extend from the podocyte and increase the surface area. [3]
Pathology
Disruption of the slit diaphragms or destruction of the podocytes can lead to massive proteinuria where large amounts of protein are lost from the blood. Proteinuria (from protein and urine) means the presence of anexcess of serum Proteins in the Urine.
An example of this occurs in the congenital disorder Finnish-type nephrosis, which is characterised by neonatal proteinuria leading to end-stage renal failure. Congenital nephrotic syndrome is an inherited disorder characterized by Protein in the Urine and swelling of the body Renal failure or kidney This disease has been found to be caused by a mutation in the nephrin gene. Nephrin is a Protein necessary for the proper functioning of the renal filtration barrier
See also
References
- ^ p_26/12652756 at Dorland's Medical Dictionary
- ^ Podocyte at eMedicine Dictionary
- ^ Physiology at MCG 7/7ch04/7ch04p08
External links
- Scanning-electron micrograph of a podocyte, from Georgetown University
- Organology at UC Davis Urinary/mammal/vasc1/vasc1 - "Mammal, renal vasculature (EM, High)
- Histology at BU 22401loa - ". Foot processes of Podocytes interdigitate with one another forming filtration slits (or slit pores) that in contrast to those in the Glomerular Endothelium Dorland's is the brand name of a family of medical reference works (including dictionaries, spellers word books and spell-check software) in various media (including eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors The Medical College of Georgia, also known as MCG, is a public medical Research university located in downtown Augusta Georgia. Georgetown University is a Jesuit Private university located in Georgetown Washington D The University of California Davis, commonly known as UC Davis, or just UCD, is a public coeducational university located in the city of Davis, For similarly-named academic institutions see Education in Boston MA. Ultrastructure of the Cell: podocytes and glomerular capillaries"
- UIUC Histology Subject 1400
- podocyte.ca at Samuel Lunenfeld Research Institute
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic