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(1) A thin layer of tissue which covers a surface, lines a cavity or divides a space or organ. A pliable sheet of tissue that covers or lines or connects organs or cells of animals. A thin layer of tissue, such as the plasma membrane on the outer layer of cells.

(2) A membrane is a very thin envelope that surrounds and protects a cell. It controls the exchanges between the cell and the exterior environment: the membrane allows the passage of certain substances and prevents the passage of others. The small structures within the cell (the organelles) are also enclosed by membranes.


cell membrane - The thin membrane that forms the outer surface of the protoplasm of a cell and regulates the passage of materials in and out of the cell. It is made up of proteins and lipids and often contains molecular receptors. The membranes of organelles within the cell are made of the same basic material as the cell membrane. In plant cells, the cell membrane is surrounded by a rigid cell wall. Also called plasma membrane

trophoblast - the membrane that forms the wall of the blastocyst in early development; aids implantation in the uterine wall; “after implantation of the blastocyst in the uterine wall the trophoblast divides into two layers, the chorion and the placenta”

chorioallantoic membrane, chorioallantois - the very vascular fetal membrane composed of the fused chorion and adjacent wall of the allantois

web - membrane connecting the toes of some aquatic birds and mammals

Bowman's capsule, capsula glomeruli, glomerular capsule - thin double membrane surrounding the glomerulus of a nephron

axolemma - outer membrane covering an axon

basilar membrane - a membrane in the cochlea that supports the organ of Corti

fetal membrane - any membrane that functions for the protection or nourishment or respiration or excretion of a developing fetus

choroid, choroid coat - a highly vascular membrane in the eye between the retina and the sclera; a dark pigmentation minimizes the scattering of light inside the eye

ciliary body - the part of the tunic of the eye between the choroid coat and the iris; “the ciliary body produces aqueous humor”

cornea - the transparent dome-shaped anterior portion of the outer covering of the eye; it covers the iris and pupil and is continuous with the sclera

diaphragm, midriff - (anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration

eardrum, myringa, tympanic membrane, tympanum - the membrane in the ear that vibrates to sound

endocranium - membrane lining the inside of the skull

endosteum - vascular membrane that lines the inner surface of long bones

ependyma - thin epithelial membrane lining the ventricles of the brain and the spinal cord canal

fertilization membrane - the membrane that forms around a fertilized ovum and prevents penetration by additional spermatozoon

hyaloid, hyaloid membrane - the transparent membrane enveloping the vitreous humor of the eye and separating it from the retina

intima - the innermost membrane of an organ (especially the inner lining of an artery or vein or lymphatic vessel)


lamella - a thin membrane that is one of the calcified layers that form bones

meninges, meninx - a membrane (one of 3) that envelops the brain and spinal cord

mucosa, mucous membrane - mucus-secreting membrane lining all body cavities or passages that communicate with the exterior

periosteum - a dense fibrous membrane covering the surface of bones (except at their extremities) and serving as an attachment for tendons and muscles; contains nerves and blood vessels that nourish the enclosed bone

perithelium - tissue layer around small blood vessels

retina - the innermost light-sensitive membrane covering the back wall of the eyeball; it is continuous with the optic nerve

sarcolemma - an extensible membrane enclosing the contractile substance of a muscle fiber

semipermeable membrane - a membrane (as a cell membrane) that allows some molecules to pass through but not others

serosa, serous membrane - a thin membrane lining the closed cavities of the body; has two layers with a space between that is filled with serous fluid

synovial membrane, synovium - a thin membrane in synovial (freely moving) joints that lines the joint capsule and secretes synovial fluid

adventitia, tunic, tunica - an enveloping or covering membrane or layer of body tissue

phospholipid - any of various compounds composed of fatty acids and phosphoric acid and a nitrogenous base; an important constituent of membranes

glossary/membrane.txt · Last modified: 2012/10/16 14:40 (external edit)