membrane (mem'bran?) [L. membrana, parchment]
1. A thin, pliable layer of tissue that lines a tube or cavity, covers an organ or structure, or separates one part from another.
2. A very thin sheet of polymer, ceramics, glass, or metal.
The structures and substances through which gases must pass as they diffuse from air to blood (oxygen) or blood to air (carbon dioxide), including the alveolar fluid and surfactant, cell of the alveolar wall, interstitial space (tissue fluid), and cell of the capillary wall. Synonym: respiratory membrane See: illustration
The delicate middle membrane of the three meninges, which enclose the brain and spinal cord. The arachnoid membrane is 5–6 cells thick. It adheres to the inner surface of the dura and is connected to the pia by a spiderweb of thin connections. Thee space between the arachnoid and pia (the subdural space) is filled with cerebrospinal fluid. Synonym: arachnoid; arachnoid mater
A single midline ligamentous structure that extends from the arch of the atlas to the borders of the foramen magnum.
A two-part extracellular layer found at the interface between some tissues, e.g., skin and dermis. . The basement membrane is made of a basal lamina along the cell surfaces, coated by a stronger collagen-rich layer, the reticular lamina
The membrane extending from the tympanic lip of the osseous spiral lamina to the crest of the spiral ligament in the cochlea of the ear. It separates the tympanic canal from the cochlear duct and supports the organ of Corti. See: illus. under organ of Corti
An artificially constructed membrane made of lipids arranged in a bilayer.
Bowman membrane See: Bowman, Sir William
Bruch membrane See: Bruch, Karl
In the embryo, the membrane that separates the oral cavity from the foregut until the fourth week of development. Synonym: pharyngeal membrane
The membrane that forms the outer boundary of a cell; it is made of phospholipids, protein, and cholesterol, with carbohydrates on the outer surface. Synonym: plasma membraneillustration
choroid membrane See: choroid
The dense fascia between the pectoralis minor and subclavius muscles.
The membrane connecting the thyroid and cricoid cartilages of the larynx.
croupous membraneFalse membrane.
Debove membrane See: Debove membrane
One of the membranes formed in the endometrium of a pregnant uterus. See: decidua
Demours membrane See: Demours membrane
Descemet membrane See: Descemet membrane
The fibrinous false membrane on the mucous surfaces in diphtheria.
dural membraneDura mater.
Any of the protective membranes or envelopes enclosing an ovum. It may be primary (formed by egg itself, as in vitelline membrane), secondary (formed by follicle cells, as in zona pellucida), or tertiary (formed by oviduct or uterus, as in albumin and shell of hen's egg).
Any of several membranes formed of elastic connective tissue fibers.
1. Nasmyth membrane.
2. The thin internal layer of cells of the enamel organ.
An excessive proliferation of retinal pigment epithelial cells and extracellular proteins on the retinal surface. This condition, which can distort vision, is typically found in people older than 50. Marked visual blurring caused by epiretinal membranes occurs in macular pucker. See: macular pucker
external limiting membrane
1. The outer layer of cells of the embryonic neural tube.
2. The membrane in the retina of the eye through which the receptor portions of the rods and cones protrude.
Fibrinous exudate on a mucous surface of a membrane, as in croup or diphtheria. Synonym: croupous membrane
A layer of elastic connective tissue possessing minute round or oval openings. It is found in the tunica intima and tunica media of medium-sized and large arteries.
Any of the membranous structures that protect and support the embryo and provide its nutrition, respiration, and excretion. The structures are yolk sac, allantois, amnion, chorion, decidua, and placenta.
A membrane composed entirely of fibrous connective tissue. Examples include the fasciae, aponeuroses, perichondrium, periosteum, dura mater, and the capsules of some organs.
1. The transparent capsule that separates membrana granulosa from the theca of the graafian follicle.
2. The internal layer of a hair follicle separating the epithelial and connective tissues.
glial cell membrane
An extremely delicate membrane, formed of foot plates of astrocytes, that surrounds all the blood vessels in the brain, spinal cord, and the lining of the pia mater, separating these vessels from the nervous tissue proper. This membrane is thought to be one of the components of the blood-brain barrier.
A fine membrane covering villi of the placenta.
Huxley membrane See: Huxley, Thomas H.
The membrane between the outer root sheath of a hair follicle and the inner fibrous layer.
The membrane that envelops the vitreous humor.
A transverse fibrous membrane uniting tongue to hyoid bone.
internal limiting membrane
1. The inner layer of ependymal cells lining the embryonic neural tube.
2. The glial membrane forming the innermost layer of the retina and the iris.
1. A fibrous membrane in the arm connecting ulna to radius.
2. A fibrous membrane in the leg connecting tibia to fibula.
laryngeal mucous membrane
The mucous membrane, glands, and cilia that characterize the lining of the larynx.
lingual mucous membrane
The mucosa covering the tongue.
masticatory mucous membrane
The mucosa of the mouth involved in the masticatory process. It is characterized by a keratinized surface epithelium, and includes the hard palate, gingiva, and dorsum of the tongue.
Any of the membranes that line passages and cavities communicating with the air, consisting of epithelium, a basement membrane, and an underlying layer of connective tissue (lamina propria). Mucus-secreting cells or glands are usually present in the epithelium but may be absent. In humans, mucous membranes and the skin prevent the entry of pathogens. Mucous membranes are normally colonized with nonpathogenic organisms that discourage colonization by pathogens because the resident organisms compete for the nutrients essential to their survival. Some mucosal surfaces in the digestive tract have special characteristics that tend to repel or kill organisms, such as the extremely high acid level on the mucosa of the stomach.
Noninvasive examination of membranes should reveal the degree of moisture, cyanosis, pallor, hyperemia, pigmentation, lesions or their absence, and hemorrhage. Pallor is seen in all anemias. If the pallor is temporary, it may indicate shock or vasomotor spasm, or it may occur in severe hemorrhages. Blanching and flushing alternately accompany aortic regurgitation.
Hyperemia of the mucous membranes is indicative of certain pathological changes in particular tissues, e, g., of the buccal mucous membrane, due to decayed teeth, traumatism, or stomatitis; of the nasal mucosa, due to ulceration of the nose, rhinitis, or inflammation; of the eyes (local irritation), due to a foreign body, ulcer, inflammation. Dryness is seen in fevers, chronic gastritis, some liver disturbances, excitement, shock, prostration, fatigue, thirst, and certain drugs.
nasal mucous membrane
The mucosa lining the nasal cavity and characterized by pseudostratified ciliated columnar epithelium with goblet cells.
Nasmyth membrane See: Nasmyth membrane
A third eyelid present in lower vertebrates and represented in humans by a fold of the conjunctiva, the plica semilunaris.
The two-layered membrane surrounding the chromosomes of a cell. The membrane has pores and its outer layer is continuous with the endoplasmic reticulum of the cell. See: nuclear envelope
A fibrous membrane closing the obturator foramen.
The membrane in the upper part of the nasal cavity that contains olfactory receptors.
oral membraneBuccopharyngeal membrane.
A double epithelial layer separating the nasal pits from the embryonic oral cavity.
A layer of gelatinous substance containing otoconia or otoliths, found on the surface of maculae in the inner ear.
palatal mucous membrane
The lining of the mouth on the hard and soft palates. The hard palate has heavily keratinized epithelium and copious mucous glands or fat in the submucosa. The mobile soft palate contains muscle in addition to mucous glands, and is much less keratinized on the surface.
An obsolete term for the periodontal ligament.
A membrane that permits passage of water and certain substances in solution. See: osmosis; selectively permeable membrane; semipermeable membrane
persistent pupillary membrane See: pupillary membrane
pharyngeal membraneBuccopharyngeal membrane.
pharyngeal mucous membrane
The lining of the pharynx. The mucosa of the nasopharynx is pseudostratified ciliated epithelium; the mucosa of the oropharynx and laryngopharynx is stratified squamous epithelium.
pial membranePia mater.
The membrane of the placenta that separates the maternal blood from fetal blood.
plasma membraneCell membrane.
A membrane resembling a serous membrane but differing in structure as the endothelium.
The transparent membrane closing the fetal pupil. If it persists after birth, it is called persistent pupillary membrane.
The granular lining of an abscess or fistula.
The lining membrane of an abscess cavity separating it from healthy tissue.
The upper portion of the elastic membrane of the larynx extending from the aryepiglottic folds to the level of the ventricular folds below.
Reissner membrane See: Reissner membrane
respiratory membraneAlveolocapillary membrane.
The membrane formed by the cuticular plates of the distal ends of supporting cells in the organ of Corti.
Ruysch membrane See: Ruysch membrane
Scarpa membrane See: Scarpa membrane
The nasal mucosa.
Schwann membrane See: Schwann, Theodore
selectively permeable membrane
A membrane that allows one substance, such as water, to pass through more readily than another, such as salt or sugar.
A membrane that allows passage of water but not substances in solution. See: osmosis
A membrane consisting of mesothelium lying on a thin layer of connective tissue that lines the closed cavities (peritoneal, pleural, and pericardial) of the body and is reflected over the organs in the cavity. Serous fluid, similar to lymph, decreases friction between the two layers.
Shrapnell membrane See: Shrapnell membrane
submucous membrane See: submucosa.
The membrane lining the capsule of a joint and secreting synovial fluid. The synovial membrane is pink, smooth, and shiny and is made of an intima lining a stronger, vascular fibrous membrane. The intima contains synoviocytes (fibroblast- and macrophage-like cells), which remove debris from the synovial fluid and synthesize some of the mucin (specifically, hyaluronic acid) of the synovial fluid. Most of the synovial fluid is filtered from the blood vessels of the outer fibrous layer of the synovial membrane. Synonym: synovium
The thin, jelly-like membrane projecting from the vestibular lip of the osseous spiral lamina and overlying the spiral organ of Corti of the ear.
The membrane joining the hyoid bone and the thyroid cartilage.
See: ear thermometry; tympanum
The three-layered membrane at the inner (medial) end of the external auditory canal, forming the lateral boundary of the middle ear cavity. The outer layer of the tympanic membrane is keratinized skin, continuous with the skin lining the external ear canal. Synonym: drum
The phospholipid bilayer first described as the typical cell membrane, then as the membrane of intracellular structures.
A membrane, usually transparent, that is permeable to oxygen and water vapor. It may be prepared with an adhesive backing that will stick only to dry skin. This type of membrane has been used in covering wounds. The membrane must be applied properly without wrinkles and changed as often as necessary to prevent excess accumulation of fluid and bacteria under it.
The membrane in the cochlea of the inner ear that separates the cochlear duct from the vestibular canal.
vestibular mucous membrane
The mucosa of the oral vestibule with its nonkeratinized stratified squamous epithelium, elastic lamina propria, and seromucous labial glands.
An obsolete term for the hymen.
The membrane that forms the surface layer of an ovum. Synonym: yolk membrane
; zona pellucida
1. The inner membrane of the choroid.
2. The innermost layer of the connective tissue sheath surrounding a hair follicle.
Wachendorf membrane See: Wachendorf membrane
yolk membraneVitelline membrane.
Medical Dictionary, © 2009 Farlex and Partners