cell membrane (redirected from Cell membranes)

cell membrane

n.

The semipermeable membrane that encloses the cytoplasm of a cell. Also called cytomembrane, plasmalemma, plasma membrane.

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cell membrane.

See plasma membrane.

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cell, centrioles of (sen´trēōls),

n.pl cylinder-shaped organelles that contain microtubules. Function is to organize spindle fibers during cell division.

cell, connective tissue,

n the fibroblast, which for purposes of clarity is characterized by such terms as
perivascular connective tissue cell or
young connective tissue cell.

cell count,

n the number of cells contained in a unit volume; usually refers to red and/or white blood cells in a unit volume of blood.

cell culture,

n living cells that are maintained in vitro in artificial media of serum and nutrients for the study and growth of certain strains, experiments in controlling diseases, or study of the reaction to certain drugs or agents.

cell cycle,

n the sequence of events that occur during the growth and division of tissue cells.

cell, cytoplasm of

n the aqueous part of the cell in which are suspended all the organelles and inclusions. Site of all metabolic activities in the cell.

cell death,

n the point in the process of dying at which vital functions have ceased at the cellular level. It precludes the use of tissue or organs as transplant donors.

cell, defense,

n a cell, mobilized within inflamed, irritated, or otherwise diseased tissue, that acts as a protective element to neutralize or wall off the foreign irritant. Defense cells include plasma cells, polymorphonuclear leukocytes, and the cells of the reticuloendothelial system.

cell, dendritic (sel dendrit´ik),

n the immune cells involved in the activation of T cells and B cells. They are primarily found in exposed tissue such as skin, the lungs, the stomach and intestines, and the membranes of the nose, but they are also found in blood. Not to be confused with dendrites.

cell differentiation,

n the development of the cells into the various basic cell units of tissue: the epithelial cell and the nerve cell, which arise from the ectodermal tissue layer of the embryo; and the blood, muscle, bone, cartilage, and other connective tissue cells, which arise from the mesodermal tissue of the embryo. The mature tissue cell has many intermediary, transitional forms that are sequential in their development from the primitive, less differentiated anlage cell forms. These intermediary forms are evident clinically in disease in blood dyscrasias, tumors, and inflammation and in health in the normal processes of growth, development, healing, and repair.

cell, endoplasmic reticulum of,

n See endoplasmic reticulum.

cell, endosteal,

n a reticular cell that is modified and identified by its location; the endosteum is a condensation of the stroma of the bone marrow.

cell, filaments of,

n.pl threadlike structures the function of which is to support the cytoskeleton; also integral parts of intercellular junctions.

cell, germ,

n a cell of an organism the function of which is to reproduce an entity similar to the organism from which the germ cell originated. Germ cells are characteristically haploid.

cell, giant,

n a large cell frequently having several nuclei.

cell, Golgi complex in,

n See Golgi apparatus.

cell homeostasis,

n See homeostasis, cell.

cell, homeostasis of

n See homeostasis, cell.

cell, inclusions of,

n.pl nonliving bodies, by-products of cellular metabolism present in the cytoplasm.

cell, Langerhans,

n.pr star-shaped cells of unknown function that appear to be permanent residents of the epithelium.

cell, lysosomes in

n.pl membranous organelles produced from the Golgi complex; contain hydrolytic enzymes, which aid intracellular digestion.

cell membrane,

n the outer covering of a cell. The membrane controls the exchange of materials between the cell and its environment.

cell, membrane of, transport through,

n the movement of biomolecules into and out of cells. See diffusion, osmosis, active transport, phagocytosis.

cell, mesenchymal

n an embryonic connective tissue cell with an outstanding capacity for proliferation and capable of further differentiation into reticular cells or osteoblasts. When persisting in the adult organism, the cells are usually arranged in loose connective tissue along the small blood vessels or in reticular fibers. They are identified by their location and capacity to differentiate into other cell types, such as smooth muscle cells in the formation of new arteries, phagocytes in inflammatory processes, and bone cells in the formation of new bone tissue.

cell, microtubules of,

n.pl See microtubule.

cell, mitochondria of,

n.pl See mitochondria.

cell, mucous,

n a mucous-secreting cell.

cell, nucleus of,

n See nucleus.

cell, outer, of the dental papillae,

n an outer cell of the dental papilla within the concavity of the enamel organ that will differentiate into dentin-secreting cells or odontoblasts.

cell, plasma,

n a cell of disputed origin (lymphatic versus undifferentiated mesenchymal cell) that is seen in chronic inflammation and certain disease states and tumors but not normally in the circulating blood. The cell is larger than a lymphocyte and has a cartwheel-like, eccentric nucleus with basophilic nuclear chromatin peripherally located. The cells synthesize antibodies (immunoglobulins).

cell, progenitor,

n a cell that is able to transform into different types of cells through replication and differentiation.

cell, replication,

n See mitosis.

cell, reticular,

n a cell of reticular connective tissue, such as in the stroma of the bone marrow, that retains both osteogenic and hematopoietic potencies; it is identified by its location, morphology, potency, and direct origin from mesenchymal cells.

cell, serous,

n a specialized glandular epithelial cell that produces enzymatic secretions. These cells have a rounded nucleus and special secretory granules, or vesicles, in their cytoplasm. Serous cells include the acinar cells of the salivary glands and pancreas, gastric chief cells, and intestinal Paneth cells.

cell, somatic

n a cell that forms parts of the body, including the cells of the skin, bone, blood, connective tissue, and internal organs. From the Greek word
soma, meaning “body.”

cell, stem,

n.pl the cells in the bone marrow from which all blood cells originate.

cell, typical,

n See cell.

cell wall,

n See cell membrane.

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membrane

a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.

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alveolocapillary membrane

a thin tissue barrier through which gases are exchanged between the alveolar air and the blood in the pulmonary capillaries.

membrane-attack complex

complement components C5-C9 which form in terminal stage of either of the complement pathways and lead to cell lysis.

basilar membrane

the lower boundary of the scala media of the ear.

Bowman's membrane

a thin layer of basement membrane between the outer layer of stratified epithelium and the substantia propria of the cornea.

Bruch's membrane

the inner layer of the choroid, separating it from the pigmented layer of the retina.

membrane carrier

a mechanism in the cell membrane of epithelial cells in the intestinal mucosa which facilitates the rapid transport of for example glucose, into the cell and thus into the bloodstream.

cell membrane

plasma membrane (below).

membrane channels

see channel.

continuous membrane

the middle of the three membranes on the outside of the yolk of the hen egg.

cricothyroid membrane

the membrane connecting the thyroid cartilage to the cricoid cartilage. It is extensive in the horse and surgical incision through it allows access to the interior of the larynx.

Descemet's membrane

the posterior lining membrane of the cornea; it is a thin hyaline membrane between the substantia propria and the endothelial layer of the cornea.

drum membrane

tympanic membrane (below).

extraembryonic m's

those that protect the embryo or fetus and provide for its nutrition, respiration and excretion; the yolk sac (umbilical vesicle), allantois, amnion, chorion, decidua and placenta.

extravitelline membrane

the outermost of the three membranes on the outside of the yolk of the hen egg.

false membrane

a membrane similar to the pseudomembrane; fibrinous exudates readily loosened from underlying tissue, as in croupous or pseudomembranous inflammation.

fenestrated membrane

one of the perforated elastic sheets of the tunica intima and tunica media of arteries.

fetal m's

see fetal membranes. See also extraembryonic membranes (above).

fibrous membrane

the strong, fibrous support layer in a joint capsule.

Henle's membrane

see henle's membrane.

hyaline membrane

1. a membrane between the outer root sheath and inner fibrous layer of a hair follicle.

2. basement membrane.

3. a homogeneous eosinophilic membrane lining alveolar ducts and alveoli, frequently found at necropsy in premature human infants. See also hyaline membrane disease.

hyoglossal membrane

a fibrous lamina connecting the under-surface of the tongue with the hyoid bone.

interosseous membrane

the membrane connecting the shaft of the fibula to the tibia.

limiting membrane

one that constitutes the border of some tissue or structure.

mucous membrane

the membrane covered with epithelium that lines many tubular organs of the body.

nictitating membrane

see membrana nictitans.

nuclear membrane

1. either of the membranes, inner and outer, comprising the nuclear envelope.

2. nuclear envelope.

olfactory membrane

the olfactory portion of the mucous membrane lining the nasal fossa.

periodontal membrane

see periodontium.

perivitelline membrane

the innermost of the three layers on the outside of the yolk in the hen egg.

placental membrane

the membrane that separates the fetal from the maternal blood in the placenta.

plasma membrane

the membrane that encloses a cell; it is composed of phospholipids, glycolipids, cholesterol and proteins. The primary structure is a lipid bilayer. Phospholipid molecules have an electrically charged 'head' that attracts water and a hydrocarbon 'tail' that repels water; they line up side by side in two opposing layers, with their heads on the inner or outer surface of the membrane and their tails in the core, from which water is excluded. The other lipids affect the structural properties of the membrane. Proteins embedded in the membrane transport specific molecules across the membrane, act as hormone receptors, or perform other functions.

membrane potential

of a cell is the voltage difference across the cell membrane resulting from the differential concentrations of sodium and potassium on either side of the membrane. The resting potential, for example in a nerve cell, is altered by the temporary opening of the sodium channels in the membrane during an action potential, allowing a redistribution of the ions.

membrane proteins

the large number of proteins attached to a cell membrane. They include integral proteins, called also intrinsic, which are embedded in the phospholipid bi-layer of the cell membrane, and peripheral proteins, called also extrinsic, because they are loosely bound and can readily be extracted without damage to the cell membrane.

pupillary membrane

a vascular membrane which occupies the pupil in the embryo stage, completely covering the anterior surface of the lens but subsequently disappears. See also persistent pupillary membrane.

Reissner's membrane

the thin anterior wall of the cochlear duct, separating it from the scala vestibuli.

Scarpa's membrane

tympanic membrane, secondary.

semipermeable membrane

one permitting passage through it of some but not all substances.

serosal membrane

see serous membrane (below).

serous membrane

the membrane lining the walls of the body cavities and enclosing the contained organs; it consists of mesothelium lying upon a connective tissue layer and it secretes a watery fluid.

shell membrane

the membrane on the outside of the soft contents of the hen egg and just inside the shell. It consists of two membranes close together, with an air cell in between.

synovial membrane

see synovial membrane.

membrane transport

transport of electrolytes across semipermeable membranes with the aid of a transporter.

unit membrane

the trilaminar structure of all cellular membranes (such as the plasma membrane, nuclear membranes, mitochondrial membranes, endoplasmic reticulum, lysosomes) as they appear in electron micrographs. The biochemical structure is a lipid bilayer.

wing membrane

the membrane comprising the wing of the bat.

yolk membrane

the membrane investing the yolk of the hen egg; it includes (from the inside out) the perivitelline, the continuous and the extravitelline membranes.