membrane /mem·brane/ (mem´brān) a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.
serous membrane,
serous membrane,
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 (2).
atlantooccipital membrane either of two midline ligamentous structures, one (the anterior ) passing from the anterior arch of the atlas to the anterior margin of the foramen magnum, and the other (the posterior ) connecting the posterior aspects of the same structures.
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 layer. 
)
Basement membrane, comprising the basal lamina and reticular lamina, in a diagram of a section through epithelial tissue.
basilar membrane of cochlear duct lamina basilaris.
Bichat's membrane fenestrated m.
Bowman's membrane a thin layer of cornea between the outer layer of stratified epithelium and the substantia propria.
Bruch's membrane the inner layer of the choroid, separating it from the pigmentary layer of the retina.
Brunn's membrane the epithelium of the olfactory region of the nose.
cloacal membrane the thin temporary barrier between the embryonic hindgut and the exterior.
Corti's membrane a gelatinous mass resting on the organ of Corti, connected with the hairs of the hair cells.
croupous membrane the false membrane of true croup.
cytoplasmic membrane plasma m.
decidual membranes , deciduous membranes decidua.
Descemet's membrane a thin hyaline membrane between the substantia propria and endothelial layer of the cornea.
diphtheritic membrane a false membrane characteristic of diphtheria, formed by coagulation necrosis.
drum membrane tympanic m.
elastic membrane one made up largely of elastic fibers.
enamel membrane
1. dental cuticle.
2. the inner layer of cells within the enamel organ of the fetal dental germ.
epiretinal membrane a pathologic membrane partially covering the surface of the retina, probably originating chiefly from the retinal pigment epithelial and glial cells.
extraembryonic membranes 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.
false membrane neomembrane; a membranous exudate, such as the diphtheritic membrane.
fenestrated membrane one of the perforated elastic sheets of the tunica intima and tunica media of arteries.
fetal membranes extraembryonic m's.
fibroelastic membrane of larynx the fibroelastic layer beneath the mucous coat of the larynx.
germinal membrane blastoderm.
glomerular membrane the membrane covering a glomerular capillary.
hemodialyzer membrane the semipermeable membrane that filters the blood in a hemodialyzer, commonly made of cuprophane, cellulose acetate, polyacrylonitrile, or polymethyl methacrylate.
hyaline membrane
1. a membrane between the outer root sheath and inner fibrous layer of a hair follicle.
2. a layer of eosinophilic hyaline material lining alveoli, alveolar ducts, and bronchioles, found at autopsy in infants who have died of respiratory distress syndrome of the newborn.
hyaloid membrane vitreous m. (1).
Jackson's membrane a web of adhesions sometimes covering the cecum and causing obstruction of the bowel.
keratogenous membrane matrix unguis.
limiting membrane one which constitutes the border of some tissue or structure.
medullary membrane endosteum.
mucous membrane the membrane lining various canals and cavities of the body.
Nasmyth's membrane dental 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.
ovular membrane vitelline m.
peridental membrane , periodontal membrane periodontal ligament.
placental membrane the membrane separating the fetal from the maternal blood in the placenta; sometimes inappropriately called the placental barrier. 
)
Placental membrane separating the blood in the fetal capillaries from the maternal blood in the intervillous space. (A), chorionic villus containing the fetal vessels and surrounded by maternal blood in the intervillous space; (B), cross-section through a villus, showing the layers of the placental membrane separating the fetal blood from the maternal blood surrounding the villus.
plasma membrane the structure, composed of lipids, proteins, and some carbohydrates, that encloses the cytoplasm of a cell, forming a selectively permeable barrier.
pupillary membrane a mesodermal layer attached to the rim or front of the iris during embryonic development.
Reissner's membrane the thin anterior wall of the cochlear duct, separating it from the scala vestibuli.
reticular membrane , reticulated membrane a netlike membrane over the spiral organ of the ear, through which pass the free ends of the outer hair cells.
membrane of round window secondary tympanic m.
Ruysch's membrane , ruyschian membrane lamina choroidocapillaris.
Scarpa's membrane secondary tympanic m.
schneiderian membrane the mucous membrane lining the nose.
secondary tympanic membrane the membrane enclosing the fenestra cochlearis.
serous membrane tunica serosa.
Shrapnell's membrane the thin upper part of the tympanic membrane.
suprapleural membrane the strengthened portion of the endothoracic fascia attached to the inner part of the first rib and the transverse process of the seventh cervical vertebra.
synaptic membrane the part of the plasma membrane of a neuron that is within a synapse.
synovial membrane
1. 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.
2. either of two membranes, superior and inferior, lining the articular capsule of the temporomandibular joint.
tectorial membrane Corti's m.
tympanic membrane the thin partition between the external acoustic meatus and the middle ear. 
)
Tympanic membrane (membrana tympanica).
undulating membrane a protoplasmic membrane running like a fin along the bodies of certain protozoa.
unit membrane the trilaminar structure of the plasma membrane and other cellular membranes (e.g., nuclear m's, mitochondrial m's) revealed by the electron microscope.
vestibular membrane of cochlear duct the thin anterior wall of the cochlear duct, separating it from the scala tympani.
vitelline membrane the cytoplasmic, noncellular membrane surrounding an oocyte.
vitreous membrane
1. a delicate boundary layer investing the vitreous body.
2. Bruch's m.
4. hyaline m. (1).
yolk membrane vitelline m.
Zinn's membrane ciliary zonule.
| serous membrane n. A thin, two-part membrane that secretes a serous fluid and lines a closed body cavity, covering the organs that lie within that cavity. Also called serosa, serous tunic. |
serous membrane,
one of the many thin sheets of tissue that line closed cavities of the body, such as the pleura lining the thoracic cavity, the peritoneum lining the abdominal cavity, and the pericardium lining the sac that encloses the heart. Between the visceral layer of serous membrane covering various organs and the parietal layer lining the cavity containing these organs is a potential space moistened by serous fluid. The fluid reduces the friction of the structures covered by the serous membrane, such as the lungs, which move against the thoracic walls in respiration. Compare mucous membrane, skin, synovial membrane.
serous membrane,
n a thin sheet of tissue that lines closed cavities of the body, such as the pleura lining the thoracic cavity and the pericardium lining the sac enclosing the heart.
membrane
a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.
alveolocapillary membrane
a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries.
membrane-attack complex
complement components C5-C9 which form in terminal stage of either of the complement pathways and lead to cell lysis.
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.
membrane carrier
a mechanism in the cell membrane of epithelial cells in the intestinal mucosa which facilitates the rapid transport of for example glucose, into the cell and thus into the bloodstream.
cell membrane
plasma membrane (below).
membrane channels
see channel.
continuous membrane
the middle of the three membranes on the outside of the yolk of the hen egg.
cricothyroid membrane
the membrane connecting the thyroid cartilage to the cricoid cartilage. It is extensive in the horse and surgical incision through it allows access to the interior of the larynx.
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.
drum membrane
tympanic membrane (below).
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.
extravitelline membrane
the outermost of the three membranes on the outside of the yolk of the hen egg.
false membrane
a membrane similar to the pseudomembrane; fibrinous exudates readily loosened from underlying tissue, as in croupous or pseudomembranous inflammation.
fenestrated membrane
one of the perforated elastic sheets of the tunica intima and tunica media of arteries.
fetal m's
see fetal membranes. See also extraembryonic membranes (above).
fibrous membrane
the strong, fibrous support layer in a joint capsule.
Henle's membrane
see henle's membrane.
hyaline membrane
1. a membrane between the outer root sheath and inner fibrous layer of a hair follicle.
3. a homogeneous eosinophilic membrane lining alveolar ducts and alveoli, frequently found at necropsy in premature human infants. See also hyaline membrane disease.
hyoglossal membrane
a fibrous lamina connecting the under-surface of the tongue with the hyoid bone.
interosseous membrane
the membrane connecting the shaft of the fibula to the tibia.
limiting membrane
one that constitutes the border of some tissue or structure.
mucous membrane
the membrane covered with epithelium that lines many tubular organs of the body.
nictitating membrane
see membrana nictitans.
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.
periodontal membrane
see periodontium.
perivitelline membrane
the innermost of the three layers on the outside of the yolk in the hen egg.
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.
membrane potential
of a cell is the voltage difference across the cell membrane resulting from the differential concentrations of sodium and potassium on either side of the membrane. The resting potential, for example in a nerve cell, is altered by the temporary opening of the sodium channels in the membrane during an action potential, allowing a redistribution of the ions.
membrane proteins
the large number of proteins attached to a cell membrane. They include integral proteins, called also intrinsic, which are embedded in the phospholipid bi-layer of the cell membrane, and peripheral proteins, called also extrinsic, because they are loosely bound and can readily be extracted without damage to the cell membrane.
pupillary membrane
a vascular membrane which occupies the pupil in the embryo stage, completely covering the anterior surface of the lens but subsequently disappears. See also persistent pupillary membrane.
Reissner's membrane
the thin anterior wall of the cochlear duct, separating it from the scala vestibuli.
Scarpa's membrane
tympanic membrane, secondary.
semipermeable membrane
one permitting passage through it of some but not all substances.
serosal membrane
see serous membrane (below).
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.
shell membrane
the membrane on the outside of the soft contents of the hen egg and just inside the shell. It consists of two membranes close together, with an air cell in between.
synovial membrane
see synovial membrane.
membrane transport
transport of electrolytes across semipermeable membranes with the aid of a transporter.
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.
wing membrane
the membrane comprising the wing of the bat.
yolk membrane
the membrane investing the yolk of the hen egg; it includes (from the inside out) the perivitelline, the continuous and the extravitelline membranes.
serous
1. pertaining to serum; thin and watery, like serum.
2. producing or containing serum.
serous atrophy
see serous atrophy.
serous cells
one of the two kinds of cells in the acinar portions of salivary glands. Contain secretory granules the precursors of salivary amylase. Their secretion is serous and of low specific gravity.
serous membrane
see serous membrane.
serous membrane inflammation
see serositis.
serous ovarian inclusion cysts
may be mistaken for cystic follicles but play no part in ovarian activity.
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