|Medical Dictionary - Dictionary of Medicine and Human Biology|
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. SYN: membrana [TA] . 2. SYN: biomembrane. [L. membrana, a skin or m. that covers parts of the body, fr. membrum, a member] adamantine m. SYN: enamel cuticle. allantoid m. SYN: allantois. alveolocapillary m. the pulmonary diffusion barrier. alveolodental m. SYN: periodontium. anal m. the dorsal portion of the embryonic cloacal m. after its division by the urorectal septum. anterior atlanto-occipital m. [TA] the fibrous layer that extends from the anterior arch of the atlas to the anterior margin of the foramen magnum of the occipital bone. SYN: membrana atlanto-occipitalis anterior [TA] . arachnoid m. SYN: arachnoid mater. atlanto-occipital m. See anterior atlanto-occipital m., posterior atlanto-occipital m.. Barkan m. a theoretical tissue covering the trabecular meshwork; thought to obstruct aqueous humor outflow and be responsible for congenital glaucoma. basal m. of semicircular duct the basal m. underlying the epithelium of the semicircular duct. SYN: basal lamina of semicircular duct, membrana basalis ductus semicircularis. 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 m.), and several glycoproteins. SYN: basement lamina, basilemma. basilar m. of cochlear duct SYN: basal lamina of cochlear duct. Bichat m. the inner elastic m. of arteries. Bogros serous m. a m. of the episcleral space (of Tenon). Bowman m. SYN: anterior limiting layer of cornea. Bruch m. SYN: lamina basalis choroideae. Brunn 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 7-week-old human embryo. SYN: 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. SYN: 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. SYN: cytolemma, cytomembrane, plasma m., plasmalemma, plasmolemma, Wachendorf m. (2) . chorioallantoic m. extraembryonic m. formed by fusion of chorion and allantois. choroid m. [TA] SYN: tela choroidea. cloacal m. a transitory m. in the caudal area of the embryo, separating the proctodeum from the cloaca; it is divided into anal and genitourinary membranes that break down during the 8th to 9th week of human development to establish the external opening for the alimentary and genitourinary tracts. closing membranes thin sheets, composed of ectoderm externally and endoderm internally, which separate the pharyngeal pouches from the overlying branchial clefts in the early embryo. SYN: pharyngeal membranes. Corti m. SYN: tectorial m. of cochlear duct. cricothyroid m. one of the bilateral membranes extending between the arch of the cricoid cartilage and the inferior edge of the thyroid lamina on each side of the midline, which is occupied by the thicker median cricothyroid ligament. SEE ALSO: conus elasticus, median cricothyroid ligament. SYN: membrana cricothyroidea. cricotracheal m. SYN: cricotracheal ligament. cricovocal m. conus elasticus. croupous m. SYN: 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. SYN: caduca, decidua, Hunter m., membrana decidua. Descemet m. SYN: posterior limiting lamina 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. SYN: tympanic m.. Duddell m. SYN: posterior limiting lamina 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. SYN: 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 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. SYN: Heuser m.. external intercostal m. [TA] the m. that replaces the external intercostal muscle anteriorly, between costal cartilages. SYN: membrana intercostalis externa [TA] . extraembryonic m. SYN: fetal m.. false m. a thick, tough fibrinous exudate or slough on the surface of a mucous m. or the skin, as seen in diphtheria. SYN: croupous m., 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. SYN: embryonic m., extraembryonic m.. fibroelastic m. of larynx [TA] 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 inferiorly. SYN: membrana fibroelastica laryngis [TA] . fibrous m. of joint capsule fibrous layer of joint capsule. Fielding m. SYN: tapetum (2) . flaccid m. SYN: flaccid part of tympanic m.. germ m., germinal m. SYN: 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. SYN: 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 membranes are collectively called the pial-glial m.. SYN: membrana limitans gliae. Henle m. SYN: lamina basalis choroideae. Henle fenestrated elastic m. SYN: elastic laminae of arteries, under lamina. Heuser m. SYN: exocelomic m.. Hunter m. SYN: deciduous m.. Huxley m. SYN: Huxley layer. hyaline m. 1. the thin, clear basement m. beneath certain epithelia; 2. SYN: glassy m. (2) . hyaloid m. SYN: posterior limiting lamina 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 membranes [TA] the membranous portion of the intercostal muscle layers between ribs. SYN: membranae intercostales [TA] , intercostal ligaments, ligamenta intercostalia. internal intercostal m. [TA] the m. that replaces the internal intercostal muscle posteriorly, medial to the angles of the ribs. SYN: membrana intercostalis interna [TA] . interosseous m. of forearm [TA] the dense m. that connects the interosseous margins of the radius and ulna, forming the radioulnar syndesmosis, and with those bones separating the flexor and extensor compartments of the forearm. SYN: membrana interossea antebrachii [TA] . interosseous m. of leg [TA] 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. SYN: membrana interossea cruris [TA] , ligamentum tibiofibulare medium. ivory m. SYN: membrana eboris. Jackson m. a thin vascular m. or veillike 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. SYN: Jackson veil. keratogenous m. SYN: nail matrix. limiting m. of retina one of two layers of the retina: internal limiting m., formed by the expanded inner ends of Müller fibers; outer limiting m., not a m. but a row of junctional complexes. SYN: membrana limitans (1) . medullary m. SYN: endosteum. mitochondrial m. the double biomembrane surrounding the mitochondrion. mucous membranes mucosa. mucous m. of bronchus mucosa of bronchi. mucous m. of ductus deferens mucosa of ductus deferens. mucous m. of esophagus mucosa of esophagus. mucous m. of female urethra mucosa of female urethra. mucous m. of gallbladder mucosa of gallbladder. mucous m. of large intestine mucosa of large intestine. mucous m. of larynx mucosa of larynx. mucous m. of male urethra SYN: mucosa of male urethra. mucous m. of nose mucosa of nose. mucous m. of pharyngotympanic auditory tube mucosa of pharyngotympanic (auditory) tube. mucous m. of pharynx SYN: mucosa of pharynx. mucous m. of small intestine mucosa of small intestine. mucous m. of stomach mucosa of stomach. mucous m. of tongue mucosa of tongue. mucous m. of trachea mucosa of trachea. mucous m. of tympanic cavity mucosa of tympanic cavity. mucous m. of ureter mucosa of ureter. mucous m. of urinary bladder mucosa of (urinary) bladder. mucous m. of uterine tube mucosa of uterine tube. mucous m. of vagina mucosa of vagina. Nasmyth m. SYN: enamel cuticle. nictitating m. SYN: plica semilunaris of conjunctiva (2) . Nitabuch m. a layer of fibrin between the boundary zone of compact endometrium and the cytotrophoblastic shell in the placenta. SYN: Nitabuch layer, Nitabuch stria. nuclear m. SYN: nuclear envelope. obturator m. [TA] the thin m. of strong interlacing fibers filling the obturator foramen and with the surrounding bone, giving origin to the obturator externus and internus muscles. SYN: membrana obturatoria [TA] . olfactory m. SYN: olfactory region of nose. oral m. SYN: buccopharyngeal m.. oronasal m. SYN: bucconasal m.. oropharyngeal m. SYN: buccopharyngeal m.. otolithic 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 otoliths (statoconia). SYN: membrana statoconiorum [TA] , statoconial m.. outer m. the larger of the two membranes of a double m.. ovular m. SYN: membrana vitellina (1) . Payr m. a fold of peritoneum that crosses over the left flexure of the colon. pericardiopleural m. SYN: pleuropericardial fold. peridental m. SYN: periodontium. perineal m. [TA] the layer of fascia extending between the ischiopubic rami inferior to the sphincter urethrae and the deep transverse perineal muscles. SYN: membrana perinei [TA] , Camper ligament, ligamentum triangulare, triangular ligament. periodontal m. periodontium. periorbital m. SYN: periorbita. pharyngeal membranes SYN: closing membranes. 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. SYN: mucosa of nose. 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. SYN: placental barrier. plasma m. SYN: cell m.. pleuropericardial m. SYN: pleuropericardial fold. pleuroperitoneal m. SYN: pleuroperitoneal fold. posterior atlanto-occipital m. [TA] the fibrous m. that attaches between the posterior arch of the atlas and the posterior margin of the foramen magnum. SYN: membrana atlanto-occipitalis posterior [TA] . 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. egg m.. proligerous m. SYN: cumulus oöphorus. proper m. of semicircular duct [TA] the meshwork of connective tissue fibers between the semicircular duct and the bony semicircular canal; it forms a delicate meshwork within the otherwise perilymph-filled perilymphatic space. SYN: membrana propria ductus semicircularis, membrana propria of semicircular duct. prophylactic m. SYN: 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. SYN: membrana pupillaris, Wachendorf m. (1) . pyogenic m. a layer of pus cells lining an abscess cavity which have not yet autolyzed. SYN: prophylactic m.. quadrangular m. [TA] portion of the fibroelastic m. of the larynx that lies superior to the laryngeal ventricle; its slightly thickened inferior edge, the vestibular ligament, unlerlies the vestibular fold of the larynx; it attaches anteriorly to the epiglottis and posteriorly to the lateral margin of the arytenoid and corniculate cartilages; its upper portion underlies the mucosa of the aryepiglottic fold, which separates the laryngeal vestibule from the piriform fossa of the laryngopharynx. SYN: membrana quadrangularis [TA] , Tourtual m.. Reissner m. SYN: vestibular surface of cochlear duct. reticular m. of spinal organ the m. formed by cuticular plates of the cells of the spiral organ of Corti; it appears netlike when viewed from above. SYN: membrana reticularis organi spiralis [TA] . Rivinus m. SYN: flaccid part of tympanic m.. round window m. SYN: secondary tympanic m.. Ruysch m. SYN: capillary lamina of choroid. Scarpa m. SYN: secondary tympanic m.. schneiderian m. SYN: mucosa of nose. Schultze m. SYN: olfactory region of nasal mucosa. secondary egg m. egg m.. secondary tympanic m. [TA] the m. closing the round window (fenestra cochleae). SYN: membrana tympani secundaria [TA] , round window m., Scarpa 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. SYN: serosa. Shrapnell m. SYN: flaccid part of tympanic m.. spiral m. tympanic surface of cochlear duct. stapedial m. [TA] the delicate mucosal layer that bridges the space between the crura and base of the stapes. SYN: membrana stapedis [TA] . statoconial m. SYN: otolithic m.. sternal m. [TA] interlacing fibers from the anterior costosternal ligaments covering the anterior surface of the sternum. SYN: membrana sterni [TA] . striated m. SYN: zona striata. suprapleural m. [TA] 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. SYN: membrana suprapleuralis [TA] , Sibson aponeurosis, Sibson fascia. synovial m. [TA] 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. SYN: membrana synovialis [TA] , stratum synoviale, synovium. tectorial m. of cochlear duct [TA] a gelatinous m. that overlies the spiral organ (Corti) in the inner ear. SYN: membrana tectoria ductus cochlearis [TA] , Corti m., tectorium (2) . tectorial m. (of median atlantoaxial joint) [TA] the upward continuation of the anterior part of the posterior longitudinal ligament attached to (spanning between) 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. SYN: membrana tectoria (articulationis atlantoaxialis medianae) [TA] , apparatus ligamentosus weitbrechti, posterior occipitoaxial ligament. tertiary egg m. egg m.. thyrohyoid m. [TA] a thin, fibrous, membranous sheet filling the gap between the hyoid bone and the thyroid cartilage. SYN: membrana thyrohyoidea [TA] , membrana hyothyroidea. Toldt m. the anterior layer of the renal fascia. Tourtual m. SYN: quadrangular m.. tympanic m. [TA] 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; it is a trilaminar m. covered with skin on its external surface, mucosa in its internal surface, is covered on both surfaces with epithelium, and, in the tense part, has an intermediate layer of outer radial and inner circular collagen fibers. SYN: membrana tympani [TA] , drum m., drum, drumhead, m. of tympanum, myringa, myrinx. m. of tympanum SYN: 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 membranes, 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. SYN: urorectal fold. uteroepichorial m. rarely used term for decidua parietalis. vaginal synovial m. SYN: synovial tendon sheath. vestibular m. vestibular surface of cochlear duct. virginal m. obsolete term for hymen. vitelline m. SYN: membrana vitellina (1) . vitreous m. 1. SYN: posterior limiting lamina 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. SYN: lamina basalis choroideae. Wachendorf m. 1. SYN: pupillary m.. 2. SYN: cell m.. yolk m. SYN: membrana vitellina. Zinn m. the anterior layer of the iris.
Removal of the membranes of a subdural hematoma. [membrane + G. ektome, excision]
A minute membrane formed of fused cilia, found in certain ciliate protozoa.
Of the appearance or character of a membrane. SYN: membranoid.
1. Partly membranous and partly cartilaginous. 2. Derived from both a mesenchymal membrane and cartilage; denoting certain bones.
Relating to or of the form of a membrane. SYN: hymenoid (1) , membranaceous.
membrum, pl .membra (mem′brum, mem′bra)
A limb; a member. [L. member] m. inferius [TA] SYN: lower limb. m. muliebre obsolete term for clitoris. m. superius [TA] SYN: upper limb. m. virile SYN: penis.
1. General term for the recollection of that which was once experienced or learned. 2. The mental information processing system that receives (registers), modifies, stores, and retrieves informational stimuli; composed of three stages: encoding, storage, and retrieval. [L. memoria] affect m. the emotional element recurring whenever a significant experience is recalled. anterograde m. m. for that which occurred after an event such as a brain injury. long-term m. (LTM) that phase of the m. process considered the permanent storehouse of information which has been registered, encoded, passed into the short-term m., coded, rehearsed, and finally transferred and stored for future retrieval; material and information retained in LTM underlies cognitive abilities. remote m. m. for events of long ago as opposed to recent events. retrograde m. m. for that which occurred before an event such as a brain injury. screen m. in psychoanalysis, a consciously tolerable m. that unwittingly serves as a cover for another associated m. which would be emotionally painful if recalled. selective m. reception or retrieval of only some of the events in an experience. senile m. m. that is good for remote events, often in contrast to current events; characteristically seen in aged or demented persons. short-term m. (STM) that phase of the m. process in which stimuli that have been recognized and registered are stored briefly; decay occurs rapidly, sometimes within seconds, but may be held indefinitely by using rehearsal as a holding process by which to recycle material over and over through STM. SYN: temporary m.. subconscious m. information not immediately available for recall. temporary m. SYN: short-term m..
Abbreviation for multiple endocrine neoplasia.
Abbreviation for multiple endocrine neoplasia, type 1.
Abbreviation for multiple endocrine neoplasia, type 2A.
The period of menstrual activity in a woman's life. [G. men, month, + akme, prime]
menadiol diacetate (men-a-di′ol)
Menadiol acetylated at both hydroxyl groups; a prothrombogenic vitamin. SYN: acetomenaphthone, vitamin K4.
menadiol sodium diphosphate
A dihydro derivative of menadione, with similar vitamin K activity.
The root of compounds that are 3-multiprenyl derivatives of m. and known as the menaquinones or vitamins K2. SYN: menaphthone, vitamin K3. m. reductase SYN: NADPH dehydrogenase (quinone). m. sodium bisulfite it possesses the same action and is used for the same purposes as m. or vitamin K; it differs, however, from m. in being water-soluble.
menaquinone (MK, MQ) (men′a-kwin′on, -kwi′non)
The class name for a series of 2-methyl-3-all-trans-polyprenyl)-1,4-naphthoquinones (vitamins K2).
Hexaprenylmenaquinone; prenylmenaquinone-6;isolated from putrified fish meal; potency is about 60% of that of phylloquinone (vitamin K1). SYN: farnoquinone, vitamin K2, vitamin K2(30).
Menaquinone-6 with a 3-heptaprenyl side chain. SYN: vitamin K2(35).
Establishment of the menstrual function; the time of the first menstrual period. [G. men, month, + arche, beginning]
menarcheal, menarchial (me-nar′ke-al)
Pertaining to the menarche.
Gregor J., Austrian geneticist, 1822–1884. See mendelian character, mendelian inheritance, mendelian ratio, M. first law, M. second law.
Kurt, German neurologist, 1874–1946. See M. instep reflex, Bechterew-M. reflex.
Dimitri (Dmitri) I., Russian chemist, 1834–1907. See mendelevium, M. law.
mendelevium (Md) (men-de-le′ve-um)
An element, atomic no. 101, atomic wt. 258.1, prepared in 1955 by bombardment of einsteinium with alpha particles. [D. Mendeléeff]
Attributed to or described by Gregor Mendel; usually referring to the behavior and the mechanism of the genetic transmission of single-locus traits.
Mendelian Inheritance in Man (MIM)
A standard, comprehensive, regularly updated reference source for traits in humans that have been shown to be mendelian or that are thought on reasonable grounds to be so. Each entry has a six-digit catalog number. Those securely established (by molecular biology or by extensive clinical studies) are marked with an asterisk.
The hereditary principles of single gene traits derived from Mendel laws.
Denoting a pattern of inheritance of a trait that corresponds phenotypically to the segregation of known or putative genes at one genetic locus.
Curtis L., U.S. physician, *1913.
Pierre E., French physician, 1859–1935. See M. disease, M. syndrome.
Karl, German gynecologist, 1864–1945. See M. pessary.
Prosper, French physician, 1799–1862. See M. disease, M. syndrome.
meningeal (me-nin′je-al, men′in-je′al)
Relating to the meninges.
Suture of the cranial or spinal meninges or of any membrane. [G. meninx (mening-), membrane, + rhaphe, suture]
meninges (me-nin′jez) [TA]
Plural of meninx.
Proliferation of vessels and meningothelial cells, associated with epilepsy and neurofibromatosis.
A benign, encapsulated neoplasm of arachnoidal origin, occurring most frequently in adults; most frequent form consists of elongated, fusiform cells in whorls and pseudolobules with psammoma bodies frequently present; meningiomas tend to occur along the superior sagittal sinus, along the sphenoid ridge, or in the vicinity of the optic chiasm; in addition to meningothelial m., fibrous, transitional, metaplastic, psammomatous, secretory, clear cell, papillary, chordoid, and lymphoplasmocytic varieties are recognized. [mening- + G. -oma, tumor] cutaneous m. a lesion in the skin and subcutis composed of meningeal cells; occurs as a developmental lesion in children or as an extension of an intracranial m. in adults. malignant m. m. that either invades brain parenchyma or metastasizes. psammomatous m. a firm cellular neoplasm derived from fibrous tissue of the meninges, choroid plexus, and certain other structures associated with the brain, characterized by the formation of multiple, discrete, concentrically laminated, calcareous bodies (psammoma bodies); most of these neoplasms are histologically benign, but may lead to severe symptoms as a result of compressing the brain. SYN: sand tumor, Virchow psammoma.
The presence of multiple meningiomas, sometimes seen in von Recklinghausen disease.
meningism (men′in-jizm, me-nin′jizm)
A condition in which the symptoms simulate a meningitis, but in which no actual inflammation of these membranes is present. SYN: pseudomeningitis.
Relating to or characterized by meningitis.
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