| membrane vesicle | <cell biology> Closed unilamellar shells formed from membranes either in physiological transport processes or else when membranes are mechanically disrupted. They form spontaneously when membrane is broken because the free ends of a lipid bilayer are highly unstable. (18 Nov 1997) |
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| membrane zippering | <cell biology> Process suggested to occur in phagocytosis in which the membrane of the phagocyte covers the particle by a progressive adhesive interaction. The evidence for such a mechanism comes from experiments in which capped B-cells are only partially internalised, whereas those with a uniform opsonising coat of antiIgG are fully engulfed. (18 Nov 1997) |
| peribacteroid membrane | <plant biology> Membrane derived from the plasma membrane of a plant cell and that surrounds the nitrogen fixing bacteroids in legume root nodules. Has a high lipid content and may regulate the passage of material from the plant cell cytoplasm to the symbiotic bacterial cell. The idea that it restricts leghaemoglobin to the peribacteroid space seems untenable since leghaemoglobin is found in the cytoplasm of some cells. (18 Nov 1997) |
| pericardiopleural membrane | A tissue fold jutting into the right or left embryonic pericardioperitoneal canal; it separates the developing pericardium from the pleural cavity and is formed by the growth of the common cardinal veins to the midline of the body. Synonym: pericardiopleural membrane, pleuropericardial membrane. (05 Mar 2000) |
| pericolic membrane syndrome | <syndrome> A symptom complex simulating chronic appendicitis, caused by congenital constricting pericolic membranes. (05 Mar 2000) |
| peridental membrane | <anatomy> Fibrous connective tissue surrounding the root of a tooth that separates it from and attaches it to the alveolar bone. (12 Dec 1998) |
| perineal membrane | The layer of fascia extending between the ischiopubic rami inferior to the sphincter urethrae and the deep transverse perineal muscles. Synonym: membrana perinei, fascia diaphragmatis urogenitalis inferior, Camper's ligament, ligamentum triangulare, perineal membrane, triangular ligament. (05 Mar 2000) |
| periodontal membrane | <anatomy> Fibrous connective tissue surrounding the root of a tooth that separates it from and attaches it to the alveolar bone. (12 Dec 1998) |
| periorbital membrane | The periosteum of the orbit. Synonym: periorbit, periorbital membrane. Origin: peri-+ L. Orbita, orbit (05 Mar 2000) |
| peripheral membrane protein | <protein> Membrane proteins that are bound to the surface of the membrane and not integrated into the hydrophobic region. Usually soluble and were originally thought to bind to integral proteins by ionic and other weak forces (and could therefore be removed by high ionic strength, for example). However, it is now clear that some peripheral membrane proteins are covalently linked to molecules that are part of the membrane bilayer (see acylated proteins and glypiation) and that there are others that fit the original definition but are perhps more appropriately considered proteins of the cytoskeleton (e.g. Band 4.1 and spectrin) or extracellular matrix (e.g. Fibronectin). (18 Nov 1997) |
| Rivinus' membrane | Triangular loose part of tympanic membrane between the malleolar folds. Synonym: pars flaccida membranae tympani, flaccid membrane, membrana flaccida, Rivinus' membrane, Shrapnell's membrane. (05 Mar 2000) |
| chorioallantoic membrane | Extraembryonic membrane formed in birds and reptiles by the apposition of the allantois to the inner face of the chorion. The chorioallantoic membrane is highly vascularised and is used experimentally as a site upon which to place pieces of tissue in order to test their invasive capacity. (18 Nov 1997) |
| ruptured membrane | <obstetrics> A term used to define the rupture of the amniotic sac, releasing the amniotic fluid and heralding the onset of labour. (17 Dec 1997) |
| circular layer of tympanic membrane | Circular fibres deep to the radiate layer of the membrane that are more abundant near the periphery; not present in the pars flaccida. Synonym: circular layer of tympanic membrane. (05 Mar 2000) |
| Ruysch's membrane | The internal layer of the choroidea of the eye, composed of a very close capillary network. Synonym: lamina choroidocapillaris, choriocapillaris, entochoroidea, lamina choriocapillaris, membrana choriocapillaris, Ruysch's membrane. (05 Mar 2000) |