1. A thin sheet or layer of pliable tissue, serving as a covering or envelope of a part, as the lining of a cavity, as a partition or septum, or to connect two structures. 2. biomembrane [L. membrana, a skin or membrane that covers parts of the body, fr. membrum, a member]
adamantine m. enamel cuticle
allantoid m. allantois
alveolocapillary m. the pulmonary diffusion barrier.
alveolodental m. periodontal ligament
anal m. the dorsal portion of the embryonic cloacal m. after its division by the urorectal septum.
anterior atlanto-occipital m. the fibrous layer that extends from the anterior arch of the atlas to the anterior margin of the foramen magnum.membrana atlanto-occipitalis anterior [NA];
arachnoid m. arachnoid
atlanto-occipital m. See anterior atlanto-occipital m., posterior atlanto-occipital m.
basal m. of semicircular duct the basal m. underlying the epithelium of the semicircular duct.membrana basalis ductus semicircularis [NA], basal lamina of semicircular duct;
basement m. an amorphous extracellular layer closely applied to the basal surface of epithelium and also investing muscle cells, fat cells, and Schwann cells; thought to be a selective filter and to serve both structural and morphogenetic functions. It is composed of three successive layers (lamina lucida, lamina densa, and lamina fibroreticularis), a matrix of collagen (of which type IV is unique to this membrane), and several glycoproteins.basement lamina, basilemma;
basilar m. the m. extending from the bony spiral m. to the basilar crest of the cochlea; it forms the greater part of the floor of the cochlear duct separating the latter from the scala tympani and it supports the organ of Corti.lamina basilaris cochleae [NA], basal lamina of cochlear, basilar lamina, membrana basilaris;
Bichat's m. the inner elastic m. of arteries.
Bogros' serous m. a m. of the episcleral space (of Tenon).
Bowman's m. anterior limiting layer of cornea
Bruch's m. lamina basalis choroideae
Brunn's m. the epithelium of the olfactory region of the nose.
bucconasal m. a thin, transient epithelial sheet separating the primitive nasal cavity from the stomodeum in the seven-week-old human embryo.oronasal m;
buccopharyngeal m. a bilaminar (ectoderm and endoderm) m. derived from the prochordal plate; after the embryonic head fold has evolved it lies at the caudal limit of the stomodeum.oral m., oropharyngeal m;
cell m. the protoplasmic boundary of all cells that controls permeability and may serve other functions through surface specializations; e.g., active ion transport absorption by formation of pinocytotic vesicles; receptor-mediated antigen recognition, etc..; its fine structure is trilaminar and consists of the electron-dense lamina externa and lamina interna with an electron-lucent lamina intermedia.cytolemma, cytomembrane, plasma m., plasmalemma, plasmolemma, Wachendorf's m. (2);
chorioallantoic m. extraembryonic m. formed by fusion of chorion and allantois.
cloacal m. a transitory m. in the caudal area of the ventral wall of the embryo, separating the endodermal from the ectodermal cloaca; it is divided into anal and genitourinary m.'s that break down during the eighth to ninth week to establish the external opening for the alimentary and genitourinary tracts.
closing m.'s thin sheets, composed of ectoderm externally and endoderm internally, which separate the pharyngeal pouches from the overlying branchial clefts in the early embryo.pharyngeal m.'s;
Corti's m. tectorial m. of cochlear duct
cricothyroid m. one of the bilateral m.'s extending between arch and the inferior edge of the thyroid lamina one each side of the midline, occupied by the thicker cricothyroid ligament. See also conus elasticus, cricothyroid ligament.membrana cricothyroidea;
cricotracheal m. cricotracheal ligament
cricovocal m. conus elasticus (1)
croupous m. false m
deciduous m. the mucous m. of the pregnant uterus that has already undergone certain changes, under the influence of the ovulation cycle, to fit it for the implantation and nutrition of the ovum; so-called because the m. is cast off after labor.membrana decidua [NA], caduca, decidua, Hunter's m;
Descemet's m. posterior limiting layer of cornea
diphtheritic m. the false m. forming on the mucous surfaces in diphtheria.
double m. two biomembrane layers, with an intermembranal space, surrounding certain organelles (e.g., mitochondria) or structures.
drum m. tympanic m
Duddell's m. posterior limiting layer of cornea
dysmenorrheal m. a m., resembling the decidua, cast off in cases of membranous dysmenorrhea.
egg m. the investing envelope of the ovum; a primary egg m. is produced from ovarian cytoplasm (e.g., a vitelline m.); a secondary egg m. is the product of the ovarian follicle (e.g., the zona pellucida); a tertiary egg m. is secreted by the lining of the oviduct (e.g., a shell).
elastic m. a m. formed of elastic connective tissue, present as fenestrated lamellae in the coats of the arteries and elsewhere.
embryonic m. fetal m
enamel m. the internal layer of the enamel organ formed by the enamel cells.
epipapillary m. 1. a congenital m. covering the optic disk; 2. the glial remnants of Bergmeister's papilla.
epiretinal m. a m., usually acquired, covering a portion of the retina and composed of fibrous tissue from metaplasia of retinal pigment epithelial cells or glia.
exocelomic m. a layer of cells delaminated from the inner surface of the blastocystic cytotrophoblast and from the envelope of the primary yolk sac during the second week of embryonic life.Heuser's m;
external intercostal m. the m. that replaces the external intercostal muscle anteriorly between costal cartilages.membrana intercostalis externa [NA];
extraembryonic m. fetal m
false m. a thick, tough fibrinous exudate on the surface of a mucous m. or the skin, as seen in diphtheria.croupous m., neomembrane, plica (2), pseudomembrane;
fenestrated m. an elastic m., as in elastic laminae of arteries.
fertilization m. a viscous m. formed on the inner surface of the vitelline m. from the cytoplasm of the egg cell after entry of the sperm, preventing the entry of additional sperm.
fetal m. a structure or tissue that develops from the fertilized ovum but does not form part of the embryo proper.embryonic m., extraembryonic m;
fibroelastic m. of larynx a layer of fibrous and elastic fibers, taking the place of the submucosa in the larynx. It is divided by the laryngeal ventricle into two parts: the quadrangular m. superiorly and the conus elasticus (1) inferiorly.membrana fibroelastica laryngis [NA];
fibrous m. fibrous articular capsule
Fielding's m. tapetum (2)
flaccid m. flaccid part of tympanic membrane
germ m. , germinal m. blastoderm
glassy m. 1. the basement m. present between the stratum granulosum and the theca interna of a vesicular ovarian follicle; it becomes very prominent in large atretic follicles; 2. the basement m. and associated connective tissue of the hair follicle.hyaline m. (2);
glial limiting m. a dense, resilient m. forming the true capsule of the brain and spinal cord, composed of the processes of astrocytes (macroglia cells) and covered throughout by the pia mater, which firmly adheres to it; the two m.'s are collectively called the pial-glial m.membrana limitans gliae;
Henle's m. lamina basalis choroideae
Henle's fenestrated elastic m. elastic laminae of arteries, under lamina
Heuser's m. exocelomic m
Hunter's m. deciduous m
Huxley's m. Huxley's layer
hyaline m. 1. the thin, clear basement m. beneath certain epithelia; 2. glassy m. (2)
hyaloid m. posterior limiting layer of cornea
hyoglossal m. posterior widening of the lingual septum connecting the root of the tongue to the hyoid bone; the inferior fibers of the genioglossus are attached to it and by this means to the upper anterior body of the hyoid bone near the midline.
inner m. the smaller of a double m.
intercostal m.'s the membranous layers between ribs.membranae intercostalia [NA], intercostal ligaments, ligamenta intercostalia;
internal intercostal m. the m. that replaces the internal intercostal muscle posteriorly, medial to the angles of the ribs.membrana intercostalis interna [NA];
interosseous m. of forearm the dense m. that connects the interosseous margins of the radius and ulna, forming the radioulnar syndesmosis, and with the bones separating the flexor and extensor compartments of the forearm.membrana interossea antebrachii [NA];
interosseous m. of leg the dense fibrous layer that connects the interosseous margins of the tibia and fibula, forming the upper portion of the tibiofibular syndesmosis and, with the bones and intermuscular septa, creating anterior and posterior comparments of the leg.membrana interossea cruris [NA], ligamentum tibiofibulare medium;
ivory m. membrana eboris
Jackson's m. a thin vascular m. or veil-like adhesion, covering the anterior surface of the ascending colon from the cecum to the right flexure; it may cause obstruction by kinking of the bowel.Jackson's veil;
keratogenous m. nail bed
limiting m. of retina one of two layers of the retina: internal limiting m. , formed by the expanded inner ends of Müller's fibers; outer limiting m. , not a m. but a row of junctional complexes.membrana limitans (1);
medullary m. endosteum
mitochondrial m. the double biomembrane surrounding the mitochondrion.
mucous m.'s mucosa
mucous m. of tympanic cavity mucosa of tympanic cavity
Nasmyth's m. enamel cuticle
nictitating m. plica semilunaris conjunctivae (2)
Nitabuch's m. a layer of fibrin between the boundary zone of compact endometrium and the cytotrophoblastic shell in the placenta.Nitabuch's layer, Nitabuch's stria;
nuclear m. nuclear envelope
obturator m. the thin m. of strong interlacing fibers filling the obturator foramen.membrana obturatoria [NA];
olfactory m. that part of the nasal mucosa having olfactory receptor cells and glands of Bowman.
oral m. buccopharyngeal m
oronasal m. bucconasal m
oropharyngeal m. buccopharyngeal m
otolithic m. statoconial m
outer m. the larger of the two m.'s of a double m.
ovular m. membrana vitellina (1)
Payr's m. a fold of peritoneum that crosses over the left flexure of the colon.
pericardiopleural m. pleuropericardial fold
peridental m. periodontal ligament
perineal m. inferior fascia of urogenital diaphragm
periodontal m. periodontal ligament
periorbital m. periorbita
pharyngeal m.'s closing m.'s
pial-glial m. the dual outer lining of the brain and spinal cord, composed of the glial limiting m. and the pia mater.
pituitary m. nasal mucosa
placental m. the semipermeable layer of fetal tissue separating the maternal from the fetal blood in the placenta; composed of: 1) endothelium of the fetal vessels in the chorionic villi, 2) stromata of the villi, 3) cytotrophoblast (negligible after the fifth month of gestation), and 4) syncytial trophoblast covering the villi; the placental m. acts as a selective m. regulating passage of substances from the maternal to the fetal blood.placental barrier;
plasma m. cell m
pleuropericardial m. pleuropericardial fold
pleuroperitoneal m. pleuroperitoneal fold
posterior atlanto-occipital m. the fibrous membrane that attaches between the posterior arch of the atlas and the posterior margin of the foramen magnum.membrana atlanto-occipitalis posterior [NA];
postsynaptic m. that part of the plasma m. of a neuron or muscle fiber with which an axon terminal forms a synaptic junction; in many instances, at least part of such a small postsynaptic m. patch shows characteristic morphological modifications such as greater thickness and higher electron-density, believed to correspond to the transmitter-sensitive receptor site of such synapses.
presynaptic m. that part of the plasma m. of an axon terminal that faces the plasma m. of the neuron or muscle fiber with which the axon terminal establishes a synaptic junction; many synaptic junctions exhibit structural presynaptic characteristics, such as conical, electron-dense internal protrusions, that distinguish it from the remainder of the axon's plasma m. See also synapse.
primary egg m. See egg m.
proligerous m. cumulus oöphorus
prophylactic m. pyogenic m
pupillary m. remnants of the central portion of the anterior layer of the iris stroma (the iridopupillary lamina) which occludes the pupil in fetal life, and normally atrophies about the seventh month of gestation. Persistent strands usually stretch across the pupil from one iris collarette to the other, without touching the pupillary margin. Failure to regress is a rare cause of congenital blindness.membrana pupillaris [NA], Wachendorf's m. (1);
pyogenic m. a layer of pus cells lining an abscess cavity which have not yet autolyzed.prophylactic m;
quadrangular m. the elastic fibra m. that extends from the ventricular fold of the larynx upward to the aryepiglottic fold; it attaches anteriorly to the epiglottis and posteriorly to the lateral margin of the arytenoid and corniculate cartilages.membrana quadrangularis [NA], Tourtual's m;
Reissner's m. vestibular m
reticular m. the m. formed by cuticular plates of the cells of the spiral organ of Corti; it appears netlike when viewed from above.membrana reticularis [NA];
Rivinus' m. flaccid part of tympanic membrane
Ruysch's m. choriocapillary layer
Scarpa's m. secondary tympanic m
schneiderian m. nasal mucosa
Schultze's m. region of olfactory mucosa
secondary egg m. See egg m.
secondary tympanic m. the m. closing the fenestra cochleae or rotunda.membrana tympani secundaria [NA], Scarpa's m;
semipermeable m. a m. that is relatively permeable to the solvent but relatively impermeable to all or at least some of the solutes in either or both of the solutions separated by the m.
serous m. serosa
Shrapnell's m. flaccid part of tympanic membrane
spiral m. tympanic wall of cochlear duct
stapedial m. the delicate mucosal layer that bridges the space between the crura and base of the stapes.membrana stapedis [NA];
statoconial m. a gelatinous m. supported by the hairs of the hair cells of the maculae of the saccule and utriculus of the inner ear; adhering to the surface are numerous crystalline particles called statoconia.membrana statoconiorum [NA], otolithic m;
sternal m. interlacing fibers from the anterior costosternal ligaments covering the anterior surface of the sternum.membrana sterni [NA];
striated m. zona striata
suprapleural m. the thickened portion of endothoracic fascia extending over the cupola of the pleura and reinforcing it; it attaches to the inner border of the first rib and to the transverse process of the seventh cervical vertebra.membrana suprapleuralis [NA], Sibson's aponeurosis, Sibson's fascia;
synovial m. the connective tissue m. that lines the cavity of a synovial joint and produces the synovial fluid; it lines all internal surfaces of the cavity except for the articular cartilage of the bones.membrana synovialis [NA], stratum synoviale [NA], synovium;
tectorial m. the upper continuation of the anterior part of the posterior longitudinal ligament attached to the upper surface of the basilar portion of the occipital bone and the bodies of the second and third cervical vertebrae; it forms a "roof" over the median atlantoaxial joint.membrana tectoria [NA], apparatus ligamentosus weitbrechti, posterior occipitoaxial ligament;
tectorial m. of cochlear duct a gelatinous m. that overlies the spiral organ (Corti) in the inner ear.membrana tectoria ductus cochlearis [NA], Corti's m., tectorium (2);
tertiary egg m. See egg m.
thyrohyoid m. a thin, fibrous, membranous sheet filling the gap between the hyoid bone and the thyroid cartilage.membrana thyrohyoidea [NA], membrana hyothyroidea;
Toldt's m. the anterior layer of the renal fascia.
Tourtual's m. quadrangular m
tympanic m. a thin tense m. forming the greater part of the lateral wall of the tympanic cavity and separating it from the external acoustic meatus; it constitutes the boundary between the external and middle ear, is covered on both surfaces with epithelium, and in the tense part has an intermediate layer of outer radial and inner circular collagen fibers.membrana tympani [NA], drum m., drum, drumhead, eardrum, m. of tympanum, myringa, myrinx;
m. of tympanum tympanic m
undulating m. , undulatory m. a locomotory organelle of certain flagellate (trypanosome and trichomonad) parasites, consisting of a finlike extension of the limiting m. with the flagellar sheath; wavelike rippling of the undulating m. produces a characteristic movement.
unit m. the trilaminar structure of the plasmalemma and other intercellular m.'s, when seen in cross-section with the electron microscope, composed of two electron-dense laminae approximately 20 Å thick separated by a less dense lamina 35 Å thick.
urogenital m. the ventral portion of the embryonic cloacal m. after its division by the urorectal septum.
urorectal m. in the embryo, urorectal septum separating the cloaca into urogenital sinus and rectum.urorectal fold;
uteroepichorial m. rarely used term for decidua parietalis.
vaginal synovial m. synovial tendon sheath
vestibular m. the m. separating the cochlear duct from the vestibular canal; it consists of squamous epithelial cells with microvilli toward the ductus, a basement m., and a thin layer of connective tissue toward the scala.membrana vestibularis [NA], paries vestibularis ductus cochlearis [NA], Reissner's m., vestibular wall of cochlear duct;
virginal m. obsolete term for hymen.
vitelline m. membrana vitellina (1)
vitreous m. 1. posterior limiting layer of cornea 2. a condensation of fine collagen fibers in places in the cortex of the vitreous body; formerly thought to form a m. or capsule at its periphery; 3. lamina basalis choroideae
Wachendorf's m. 1. pupillary m 2. cell m
yolk m. membrana vitellina
Zinn's m. the anterior layer of the iris.
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