embryonic stem cell

embryonic stem cell

totipotent cells composing the inner cell mass of the blastocyst.

embryonic stem cell

Abbreviation: ES cell

A cell from the inner cell mass of the blastocyst (the 3-5 day old mammalian embryo) that can give rise to all the somatic cells of the body. Embryonic stem cells can be maintained as pure stem cell cultures.

See: adult stem cell

See also: cell

embryonic stem cell (ESC)

1. A cell taken from an early embryo and intended for therapeutic application of its totipotential property.

2. A cell derived from an embryo resulting from a donated egg whose nucleus has been removed and replaces by a cell from a prospective patient. During pregnancy some ESCs pass across the placental barrier and enter the mothers bloodstream. There are suggestions that these stem cells may repair damaged maternal organs, including the brain. Cells can be derived from umbilical cord blood that appear to have most of the properties of ESCs.

cell

1. the basic structural unit of living organisms.

2. a small more or less enclosed space.

All living cells arise from other cells, either by division of one cell to make two, as in mitosis and meiosis, or by fusion of two cells to make one, as in the union of the sperm and ovum to make the zygote in sexual reproduction.

All cells are bounded by a structure called the cell membrane or plasma membrane, which is a lipid bilayer composed of two layers of phospholipids. Each layer is one molecule thick with the charged, hydrophilic end of the lipid molecules on the surface of the membrane and the uncharged hydrophobic fatty acid tails in the interior of the membrane.

Cells are divided into two classes, eukaryotic cells and prokaryotic cells:

Eukaryotic cells have a true nucleus, which contains the genetic material, composed of the chromosomes, each of which is a long linear deoxyribonucleic acid (DNA) molecule associated with protein. The nucleus is bounded by a nuclear membrane, which is composed of two lipid bilayer membranes.

Prokaryotic cells, the bacteria, have no nucleus, and their genetic material, consisting of a single circular naked DNA molecule, is not separated from the rest of the cell by a nuclear membrane.

Eukaryotic cells are larger and more complex than prokaryotic cells. They also have membrane-bounded structures, such as mitochondria, chloroplasts, Golgi apparatus, endoplasmic reticulum and lysosomes, that prokaryotic cells lack.

The contents of a cell are referred to collectively as the protoplasm. In eukaryotic cells the contents of the nucleus are referred to as nucleoplasm and the rest of the protoplasm as the cytoplasm.

The lipid bilayer of eukaryotic cells is impermeable to many substances, such as ions, sugars and amino acids; however, membrane proteins selectively move specific substances through the cell membrane by active or passive transport. Water, gases such as oxygen and carbon dioxide, and nonpolar compounds pass through the cell membrane by diffusion. Materials can also be engulfed and taken into the cell enclosed in a portion of the cell membrane. This is called phagocytosis when solids are ingested and pinocytosis when liquids are ingested. The reverse process is called exocytosis. All of these processes permit the cell to maintain an internal environment different from its exterior. See also body fluids.

The cells of the body differentiate during development into many specialized types with specific tasks to perform. Cells are organized into tissues and tissues into organs. Embedded in the cell membrane are a wide range of molecules that vary with the cell type and are typically composed of proteins or glycoproteins that have a cytoplasmic transmembrane and external domains. These molecules serve as cell receptors and are involved in signal transduction for a wide range of ligands, including hormones, cytokines and incidentally serve as receptors for viruses and drugs.

See also betz cells, gaucher's cells, golgi's cells, hela cells, hürthle cell, kupffer's cells, merkel cell, mesangial cell, neuroendocrine cell.

Structure of the cell as seen by light microscopy. By permission from Guyton R, Hall JE, Textbook of Medical Physiology, Saunders, 2000

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accessory c's

macrophages involved in the processing and presentation of antigens making them immunogenic.

acinar cell, acinous cell

any of the cells lining an acinus, especially applied to the zymogen-secreting cells of the pancreatic acini.

adherent cell

one that adheres to the glass or plastic container in cell cultures, to form the monolayer. See also cell culture.

alpha c's

1. cells in the islets of Langerhans that secrete glucagon.

2. acidophilic cells of the anterior pituitary.

APUD c's

see apud cells.

argentaffin c's

enterochromaffin cells containing cytoplasmic granules capable of reducing silver compounds, located throughout the gastrointestinal tract, chiefly in the basilar portions of the gastric glands and the crypts of Lieberkühn. They secrete serotonin.

band cell

an immature neutrophil in which the nucleus is not lobulated but is in the form of a continuous band, horseshoe shaped, twisted or coiled. Called also band-form granulocyte and stab cell.

basal cell

an early keratinocyte, present in the basal layer of the epidermis.

basket c's

cells in the cerebellar cortex whose axons carry basket-like groups of fibrils which enclose the cell body of each Purkinje cell.

beta c's

1. basophilic cells in the pancreas that secrete insulin and make up most of the bulk of the islets of Langerhans; they contain granules that are soluble in alcohol.

2. basophilic cells of the anterior pituitary.

blood cell

one of the formed elements of the blood. See also blood.

cell body

the nucleus of the cell and the adjacent cytoplasm in cells which have processes, e g. neurons which consist of a cell body, an axon and dendrites.

bone cell

a nucleated cell in the lacunae of bone. Called also osteocyte.

cartilage cell

chondrocyte.

chromaffin c's

cells whose cytoplasm shows fine brown granules when stained with potassium bichromate, occurring in the adrenal medulla and in scattered groups in various organs and throughout the body.

cleavage cell

any of the cells derived from the fertilized ovum by mitosis; a blastomere.

cell count

see erythrocyte, leukocyte, milk cell counts.

cell culture

see cell culture.

cell cycle

see cell cycle.

daughter cell

a cell formed by division of a mother cell.

cell dehydration

fluid loss from cells due to elevation of the osmotic pressure of blood and tissue fluid; a potent stimulus to thirst.

dendritic cell

macrophage-like cells with long, filamentous processes located in the cortex of lymph nodes and the skin. Important in antigen trapping, processing and presentation. See also langerhans' cell.

cell differentiation

the process whereby cells become specialized usually with concurrent loss of reproductive capacity.

embryonic stem cell

a stem cell of fetal origin. See stem cell (below).

epithelioid cell

enlarged macrophages with enlarged lysosomes and much endoplasmic reticulum. May fuse to form multinucleated giant cell (below).

epsilon cell

one of the groups of acidophilic cells in the adenohypophysis. Contains granules that stain with azocarmine dye.

foam cell

a cell with a vacuolated appearance due to the presence of complex lipoids; seen in xanthoma.

cell fusion

see syncytial giant cell.

ganglion cell

a large nerve cell, especially one of those of the spinal ganglia.

germ cell

see germ cell.

giant cell

a very large, multinucleate cell; applied to megakaryocytes of bone marrow, to giant cells formed by coalescence and fusion of macrophages occurring in infectious granulomas and about foreign bodies, and to certain cancer cells.

glial c's

neuroglial cells.

goblet cell

a unicellular mucous gland found in the epithelium of various mucous membranes, especially that of the respiratory passages and intestines.

granular cell

one containing granules, such as a keratinocyte in the stratum granulosum of the epidermis, when it contains a dense collection of darkly staining granules.

gustatory cell

see taste bud.

heart failure c's, heart lesion c's

iron-containing, rust-colored macrophages found in the pulmonary alveoli in congestive heart failure.

helmet cell

schistocyte.

helper cell

a subset of T lymphocytes which cooperate with B and other T lymphocytes for the synthesis of antibodies to many antigens; they play an integral role in immunoregulation.

hybrid cell

a mononucleate cell produced from a binucleate heterokaryon after the latter undergoes mitosis. Such cells are initially unstable, tending to lose randomly some of the double complement of chromosomes. Used for mapping genes to particular chromosomes. See also heterokaryon, hybridoma.

immunologically competent cell

see immunocyte.

interstitial c's

the cells of the connective tissue of the ovary or of the testis (Leydig's cells) which furnish the internal secretion of those structures, i.e. testosterone.

islet c's

cells composing the islets of Langerhans in the pancreas. See alpha cells, beta cells (above).

juxtaglomerular c's

specialized cells, containing secretory granules, located in the tunica media of the afferent glomerular arterioles. They cause aldosterone production by secreting the enzyme renin and play a role in the regulation of blood pressure and fluid balance.

K c's, killer c's

T lymphocytes or null lymphocytes that have cytotoxic activity against target cells coated with specific IgG antibody.

lacis cell

accumulation of cells between the arterioles at the glomerular hilus. Called also granular cell.

lacunar cell

precursor of the malignant interdigitating reticular cell in Hodgkin-like lymphoma in humans.

LE cell

a mature neutrophilic polymorphonuclear leukocyte characteristic of lupus erythematosus. See also lupus erythematosus (le) cell.

Leydig's c's

interstitial cells of the testis, which secrete testosterone.

cell line

see cell culture.

lutein c's

the plump, pale-staining, polyhedral cells of the corpus luteum.

lymph cell

lymphocyte.

lymphoid c's

lymphocytes and plasma cells.

mast cell

a connective tissue cell that has basophilic, metachromatic cytoplasmic granules that contain histamine, heparin, hyaluronic acid, slow-reacting substance of anaphylaxis (SRS-A), and, in some species, serotonin. Have Fc receptors specific for IgE in the cell membrane.

cell-mediated immune reaction

see cellular immunity.

cell migration

movement of cells from their place of origin to other tissues; one of the fundamental processes of development.

microglial cell

see microglia. See also neuroglia cells (below).

milk cell count

see milk cell counts.

mother cell

a cell that divides to form new, or daughter, cells.

Mott cell

a plasma cell with large, clear cytoplasmic pockets.

natural killer c's, NK c's

cells capable of mediating cytotoxic reactions without themselves being specifically sensitized against the target.

nerve cell

any cell of the nervous system; a neuron.

cell nests

see isogenous groups.

neuroglia c's, neuroglial c's

see neuroglia.

null c's

lymphocyte-like cells that lack specific antigen receptors and other surface markers characteristic of B and T lymphocytes; they include K and NK cells; their numbers are elevated in active systemic lupus erythematosus and other disease states.

olfactory c's

a set of specialized cells of the mucous membrane of the nose; the receptors for smell.

parafollicular c's

see c cell.

Pick's c's

round, oval or polyhedral cells with foamy, lipid-containing cytoplasm found in the bone marrow and spleen in Niemann-Pick disease.

plasma cell

a spherical or ellipsoidal cell with a single, eccentrically placed nucleus containing dense masses of chromatin in a wheel-spoke arrangement, an area of perinuclear clearing which contains the Golgi apparatus, and generally abundant cytoplasm. Plasma cells are produced by cell division of B lymphocytes following antigen stimulation and are involved in the synthesis and release of antibody. Called also plasmacyte and plasmocyte.

prickle cell

a dividing keratinocyte of the prickle-cell layer of the epidermis, with delicate radiating process connecting with other similar cells.

prokaryotic cell

see prokaryote.

Purkinje's c's

large branching cells of the middle layer of the cerebellar cortex.

red cell, red blood cell

erythrocyte.

Reed-Sternberg c's

giant histiocytic cells, typically multinucleate, which are the common histological characteristic of Hodgkin's disease in humans.

reticular c's

the cells forming the reticular fibers of connective tissue; those forming the framework of lymph nodes, bone marrow and spleen. They are weakly phagocytic, stromal in origin and are distinct from the monocyte-macrophage system.

reticuloendothelial cell

a cell of the reticuloendothelial system.

Schwann cell

any of the large nucleated cells whose cell membrane spirally enwraps the axons of myelinated peripheral neurons supplying the myelin sheath between two nodes of Ranvier.

Sertoli c's

elongated cells in the tubules of the testes to which the spermatids become attached; they provide support, protection and, apparently, nutrition until the spermatids are transformed into mature spermatozoa.

sickle cell

a crescentic or sickle-shaped erythrocyte seen in some humans and deer. The abnormal shape caused by the presence of varying proportions of hemoglobin S.

signet-ring cell

a cell in which the nucleus has been pressed to one side by an accumulation of intracytoplasmic mucin.

somatic c's

the cells of the body other than the germ cells.

cell sorting

see fluorescence-activated cell sorter.

cell specialization

conversion of a simple cell type into a specialized cell type capable of a special function, e.g. a secretory cell; a major part of the growth of an embryo and the differentiation of basic mesenchymal tissue into specialized organs.

spindle cell

spindle shaped cells of the dermis or subcutis; principal component of spindle cell tumors.

spur cell

spiculed mature erythrocyte.

squamous c's

flat, scalelike epithelial cells.

stab cell

see band cell (above).

stellate cell

any star-shaped cell, as a Kupffer cell or astrocyte, having many filaments extending in all directions.

stem cell

1. any precursor cell.

2. a primitive hematopoietic cell that is capable of self-replicating or differentiating into precursor cells of erythrocytes or any of the leukocytes.

stipple cell

an erythrocyte containing granules that take a basic or bluish stain with Wright's stain.

suppressor c's

a not well defined subset of T lymphocytes that are reported to inhibit antibody and cell-mediated immune responses. They may play a role in immunoregulation, and are believed to be abnormal in various autoimmune and other immunological disease states. See also T lymphocytes.

target cell

1. an abnormally thin erythrocyte showing, when stained, a dark center and a peripheral ring of hemoglobin, separated by a pale, unstained zone containing less hemoglobin; seen in various anemias and other disorders. Called also codocyte.

2. any cell selectively affected by a particular agent, such as a hormone or drug.

3. cell containing nonself antigens in its cell membranes that is a target for nonimmune and immune cytolysis, e.g. virus-infected or tumor cell.

taste c's

cells in the taste buds associated with the nerves of taste.

cell therapy

see glandular therapy.

totipotential cell

an embryonic cell that is capable of developing into any type of body cell.

Türk's cell

a lymphocyte with increased basophilia.

visual c's

the neuroepithelial elements of the retina.

white cell, white blood cell

leukocyte.

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embryonic

emanating from or pertaining to embryo. See also embryo.

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embryonic death

see early embryonic mortality (below).

embryonic disk

larger cells of the mammalian blastocyst which develop into the embryo.

early embryonic mortality

death of the embryo, i.e. before it becomes a fetus; a principal cause of temporary infertility in farm livestock. Amongst causes are errors in timing of insemination, chromosomal defects, asynchronous development of the endometrium.

embryonic period

see embryo.

embryonic regulation

ability of embryonic tissues to recognize changes in their size and location and to make the necessary adjustments to form the disk-shaped assembly of appropriate structures.

embryonic stem cell

stem cell of fetal origin.

embryonic vesicle

see chorionic vesicle.