| membrana vestibularis | The membrane separating the cochlear duct from the vestibular canal; it consists of squamous epithelial cells with microvilli toward the ductus, a basement membrane, and a thin layer of connective tissue toward the scala. Synonym: membrana vestibularis, paries vestibularis ductus cochlearis, Reissner's membrane, vestibular wall of cochlear duct. (05 Mar 2000) |
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| membrana vibrans | The greater portion of the tympanic membrane which is tense and firm, contrasting with the small triangular flaccid part of tympanic membrane. Synonym: pars tensa membranae tympani, membrana tensa, membrana vibrans. (05 Mar 2000) |
| membrana vitellina | The membrane enveloping the yolk; specifically, the thickened cell membrane of large-yolked ova. Synonym: ovular membrane, vitelline membrane. Sometimes used to designate the zona pellucida of a mammalian ovum. Synonym: yolk membrane. (05 Mar 2000) |
| membrana vitrea | A transparent homogeneous acellular layer between the substantia propria and the endothelial layer of the cornea; considered to be a highly developed basement membrane. Synonym: lamina limitans posterior corneae, membrana vitrea, Descemet's membrane, Duddell's membrane, entocornea, hyaloid membrane, lamina elastica posterior, limiting layers of cornea, membrana hyaloidea, posterior elastic layer, tunica vitrea, vitreous membrane. (05 Mar 2000) |
| membranaceous | 1. Same as Membranous. 2. <botany> Thin and rather soft or pliable, as the leaves of the rose, peach tree, and aspen poplar. Origin: L. Membranaceus. Source: Websters Dictionary (01 Mar 1998) |
| membranae intercostalia | The membranous layers between ribs. Synonym: membranae intercostalia, intercostal ligaments, ligamenta intercostalia. (05 Mar 2000) |
| membranate | Of the nature of a membrane. (05 Mar 2000) |
| membrane | A thin layer of tissue which covers a surface, lines a cavity or divides a space or organ. (18 Nov 1997) |
| membrane attack complex | <immunology> A term originally used to refer to the heat labile factor in serum that causes immune cytolysis, the lysis of antibody coated cells and now referring to the entire functionally related system comprising at least 20 distinct serum proteins that is the effector not only of immune cytolysis but also of other biologic functions. Complement activation occurs by two different sequences, the classic and alternative pathways. The proteins of the classic pathway are termed components of complement and are designated by the symbols C1 through C9. C1 is a calcium dependent complex of three distinct proteins C1q, C1r and C1s. The proteins of the alternative pathway (collectively referred to as the properdin system) and complement regulatory proteins are known by semisystematic or trivial names. Fragments resulting from proteolytic cleavage of complement proteins are designated with lower case letter suffixes, for example, C3a. Inactivated fragments may be designated with the suffix i, for example C3bi. Activated components or complexes with biological activity are designated by a bar over the symbol for example C1 or C4b, 2a. The classic pathway is activated by the binding of C1 to classic pathway activators, primarily antigen-antibody complexes containing IgM, IgG1, IgG3, C1q binds to a single IgM molecule or two adjacent IgG molecules. The alternative pathway can be activated by IgA immune complexes and also by nonimmunologic materials including bacterial endotoxins, microbial polysaccharides and cell walls. Activation of the classic pathway triggers an enzymatic cascade involving C1, C4, C2 and C3, activation of the alternative pathway triggers a cascade involving C3 and factors B, D and P. Both result in the cleavage of C5 and the formation of the membrane attack complex. Complement activation also results in the formation of many biologically active complement fragments that act as anaphylatoxins, opsonins or chemotactic factors. (05 Jan 1998) |
| membrane bone | A bone that develops embryologically within a membrane of vascularised primitive mesenchymal tissue without prior formation of cartilage. (05 Mar 2000) |
| membrane capacitance | The electrical capacitance of a membrane. Plasma membranes are excellent insulators and dielectrics: capacitance is the measure of the quantity of charge that must be moved across unit area of the membrane to produce unit change in membrane potential and is measured in Farads. most plasma membranes have a capacitance around 1 microfarad cmexp 2. (18 Nov 1997) |
| membrane depolarisation | The process or act of neutralising polarity, depriving of polarity, or the result of such action; reduction to an unpolarised condition. <physiology> The reversal of the resting potential in excitable cell membranes when stimulated i.e., the tendency of the cell membrane potential to become positive with respect to the potential outside the cell. A positive shift in a cells resting potential (that is normally negative), thus making it numerically smaller and less polarized, for example 90mV to 50mV. <optics> Depolarisation of light, a change in the plane of polarization of rays, especially by a crystalline medium, such that the light which had been extinguished by the analyser reappears as if the polarization had been anulled. The word is inappropriate, as the ray does not return to the unpolarised condition. Origin: Cf. F. Depolarisation. (27 Oct 1998) |
| membrane dipeptidase | <enzyme> Renal dipeptidase which metabolises thienamycin and related carbapenem antibiotic Registry number: EC 3.4.13.19 Synonym: dehydropeptidase-i, dehydropeptidase I, microsomal dipeptidase (26 Jun 1999) |
| membrane enzyme | <enzyme> An enzyme present or embedded in a biomembrane. (05 Mar 2000) |
| membrane expansion theory | That adsorption of anaesthetics into membranes so alters membrane volume and/or configuration that membrane function is affected in such a way as to produce anaesthesia. (05 Mar 2000) |