germ cell
(redirected from Primordial germ cells)Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia.
sex cell
a sperm or an oocyte.
Synonym(s): germ cell
germ cell
n.
An ovum or a sperm cell or one of its developmental precursors.
germ cell
1 a sexual reproductive cell in any stage of development, from the primordial embryonic form to the mature gamete.
2 an ovum or spermatozoon or any of their preceding forms.
sex cell
(seks sel)A sperm or an oocyte.
Synonym(s): germ cell.
Synonym(s): germ cell.
germ cell
see GAMETE.Germ cell
One of the cells that ordinarily develop into eggs or sperm (also sperm and eggs).
Mentioned in: Choriocarcinoma
sex cell
(seks sel)Sperm or oocyte.
Synonym(s): germ cell.
Synonym(s): germ cell.
germ cell,
n a sexual reproductive cell in any stage of development; that is, an ovum or spermatozoon or any of their preceding forms.
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
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
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.
germ
1. old-fashioned and lay term for a pathogenic microorganism.
2. living substance capable of developing into an organ, part or organism as a whole; a primordium. Commonly used to refer to the embryos of wheat grains which are removed during milling and sold separately as wheat germ.
germ cell
direct descendants of the primordial cells which originate from the yolk sac endoderm and migrate to the gonadal ridges of the embryo, where they give rise to either ova or spermatozoa. Called also gonocytes, sex cells.
germ cell tumor
a rare tumor in dogs, similar to more common lesions in humans. Similar to pituitary adenomas in distribution and cellular characteristics.
germ line
the genetic material as it is transferred via the gametes, before being modified by somatic recombination or mutation.
germ line cells
gametes.
germ line transmission
a mode of transmission, particularly of retroviruses, whereby the genome of the virus is integrated into the chromosomal DNA and transmitted via gametes to offspring.
germ plasma evaluation program
a planned investigative, large scale breeding program aimed at accumulating comparative information on the relative performance of various breeds and crossbreeds of agricultural animals.
germ theory
1. all organisms are developed from a cell.
2. infectious diseases are of microbial origin.
germ tube
a tube-like structure that develops during the growth of some fungi and becomes a hypha; a feature of the yeast, Candida albicans.
wheat germ
see wheat germ.