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(memʹbrānʺ) [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.

alveolocapillary m. The membrane 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. SYN: respiratory membrane. SEE: illus.





arachnoid m. The delicate middle membrane of the three meninges, which enclose the brain and spinal cord. The arachnoid membrane is 5–6 cells thick. It is adherent to the inner surface of the dura by dural border cells. It is connected to the pia mater by a spiderweb of thin connections, owing to their common embryological origin as the leptomeninges. The space between the arachnoid and pia (the subdural space) is filled with cerebrospinal fluid. SYN: arachnoid; arachnoid mater.

atlanto-occipital m. A single midline ligamentous membrane that extends from the arch of the atlas to the borders of the foramen magnum.

basement m. A two-part extracellular membrane 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 (reticular lamina).

basilar m. 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.

black m. An artificially constructed membrane made of lipids arranged in a bilayer.

Bowman m. SEE: under Bowman, Sir William.

Bruch m. SEE: under Bruch, Karl.

buccopharyngeal m. In the embryo, the membrane that separates the oral cavity from the foregut until the fourth week of development. SYN: oral membrane; pharyngeal membrane.

cell m. The membrane that forms the outer boundary of a cell. It is made of phospholipids, protein, and cholesterol, with carbohydrates on the outer surface. SYN: plasma membrane. SEE: illus.

choroid m. SEE: choroid.

cricothyroid m. The membrane connecting the thyroid and cricoid cartilages of the larynx.

decidual m. Any of the membranes formed in the endometrium of a pregnant uterus. SEE: decidua.

Descemet m. SEE: Descemet membrane.

diphtheritic m. The fibrinous false membrane on the ...

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