unit membrane


membrane

 [mem´brān] a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ. adj., adj mem´branous.alveolar-capillary membrane (alveolocapillary membrane) a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries. Called also blood-air barrier and blood-gas barrier.alveolodental membrane periodontium.arachnoid membrane arachnoid.basement membrane a sheet of amorphous extracellular material upon which the basal surfaces of epithelial cells rest; it is also associated with muscle cells, Schwann cells, fat cells, and capillaries, interposed between the cellular elements and the underlying connective tissue. It comprises two layers, the lamina" >basal lamina and the lamina" >reticular lamina, and is composed of Type IV collagen (which is unique to basement membranes), laminin, fibronectin, and heparan sulfate proteoglycans.basilar membrane the lower boundary of the scala media of the ear.Bowman's membrane a thin layer of basement membrane between the outer layer of stratified epithelium and the substantia propria of the cornea.Bruch's membrane the inner layer of the choroid, separating it from the pigmented layer of the retina.cell membrane plasma membrane.decidual m's (deciduous m's) decidua.Descemet's membrane the posterior lining membrane of the cornea; it is a thin hyaline membrane between the substantia propria and the endothelial layer of the cornea.diphtheritic membrane the peculiar false membrane characteristic of diphtheria, formed by coagulation necrosis.drum membrane tympanic membrane.epiretinal membrane a pathologic membrane partially covering the surface of the retina, probably originating chiefly from the retinal pigment epithelial and glial cells; membranes peripheral to the macula are generally asymptomatic, while those involving the macula or adjacent to it may cause reduction in vision, visual distortion, and diplopia.extraembryonic m's those that protect the embryo or fetus and provide for its nutrition, respiration, and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua, and placenta. Called also fetal membranes.false membrane a membranous exudate, such as the diphtheritic membrane; called also neomembrane.fenestrated membrane one of the perforated elastic sheets of the tunica intima and tunica media of arteries.fetal m's extraembryonic membranes.hemodialyzer membrane the semipermeable membrane that filters the blood in a hemodialyzer, commonly made of cuprophane, cellulose acetate, polyacrylonitrile, polymethyl methacrylate, or polysulfone.Henle's membrane fenestrated membrane.high efficiency membrane a hemodialyzer membrane that has clearance characteristics that increase progressively with increases in dialysis blood flow rates; this usually implies that the membrane is not a high flux membrane.high flux membrane a hemodialyzer membrane that has a high permeability to fluids and solutes and thus a high rate of clearance of fluids and solutes composed of large molecules.hyaline membrane 1. a membrane between the outer root sheath and inner fibrous layer of a hair follicle.2. basement membrane.3. a homogeneous eosinophilic membrane lining alveolar ducts and alveoli, frequently found at autopsy of infants that were preterm. See also hyaline membrane disease.hyoglossal membrane a fibrous lamina connecting the undersurface of the tongue with the hyoid bone.impaired oral mucous membrane a nursing diagnosis approved by the North American Nursing Diagnosis Association, defined as disruptions of the lips and soft tissue of the oral cavity. Changes in the integrity and health of the oral membrane" >mucous membrane can occur as a characteristic of such medical disorders as periodontal disease, uncontrolled diabetes mellitus, oral cancer, and infection with herpes. Chemical irritants such as alcohol and tobacco can also adversely affect the oral mucous membrane, as can mechanical trauma due to broken teeth, poorly fitting dentures, and endotracheal intubation. Other etiologic factors include dehydration, mouth breathing, poor oral hygiene, radiation to the head or neck, and antineoplastic agents.
Preventive measures that can help maintain the health and integrity of the oral mucosa will depend on the cause. Routinely brushing and flossing the teeth during the day and at bedtime can help avoid dental caries and periodontal disease. Some patients may need instruction in the proper procedure for cleaning the teeth and removing debris and plaque, or they may need assistance in devising ways to cope with physical disabilities that make good oral hygiene difficult for them. Patients who are unconscious or unable to perform self-care activities should have mouth care as often as needed to keep the mouth clean and moist and avoid aspiration of debris and infectious microorganisms. Adequate hydration and a lip lubricant can help avoid alterations in the oral mucosa and promote comfort.limiting membrane one that constitutes the border of some tissue or structure.mucous membrane the membrane covered with epithelium that lines the tubular organs of the body.Nasmyth's membrane primary cuticle.nuclear membrane 1. either of the membranes, inner and outer, comprising the nuclear envelope.2. nuclear envelope.olfactory membrane the olfactory portion of the mucous membrane lining the nasal fossa.placental membrane the membrane that separates the fetal from the maternal blood in the placenta.plasma membrane the membrane that encloses a cell; it is composed of phospholipids, glycolipids, cholesterol, and proteins. The primary structure is a lipid bilayer. Phospholipid molecules have an electrically charged “head” that attracts water and a hydrocarbon “tail” that repels water; they line up side by side in two opposing layers with their heads on the inner or outer surface of the membrane and their tails in the core, from which water is excluded. The other lipids affect the structural properties of the membrane. Proteins embedded in the membrane transport specific molecules across the membrane, act as hormone receptors, or perform other functions.Reissner's membrane the thin anterior wall of the cochlear duct, separating it from the scala vestibuli.membrane of round window secondary tympanic membrane.Scarpa's membrane tympanic membrane, secondary.semipermeable membrane one permitting passage through it of some but not all substances.serous membrane the membrane lining the walls of the body cavities and enclosing the contained organs; it consists of mesothelium lying upon a connective tissue layer and it secretes a watery fluid.synovial membrane the inner of the two layers of the articular capsule of a synovial joint; composed of loose connective tissue and having a free smooth surface that lines the joint cavity.tympanic membrane see tympanic membrane.tympanic membrane, secondary the membrane enclosing the window" >round window; called also Scarpa's membrane.unit membrane the trilaminar structure of all cellular membranes (such as the plasma membrane, nuclear membranes, mitochondrial membranes, endoplasmic reticulum, lysosomes) as they appear in electron micrographs. The biochemical structure is a lipid bilayer.virginal membrane hymen.vitelline membrane the external envelope of an ovum.vitreous membrane 1. Descemet's membrane.2. hyaline membrane (def. 1).3. Bruch's membrane.4. a delicate boundary layer investing the vitreous body.

u·nit mem·brane

the trilaminar structure of the plasmalemma and other intercellular membranes, when seen in cross-section with the electron microscope, composed of two electron-dense laminae, each approximately 2.5 nm thick, separated by a less dense lamina 2.5-3.5 nm thick.

u·nit mem·brane

(yū'nit mem'brān) The trilaminar structure of the plasmalemma and other intercellular membranes, when seen in cross-section with the electron microscope, composed of two electron-dense laminae separated by a less dense lamina.