a group or layer of similarly specialized cells that together perform certain special functions.
adipose tissue connective tissue made of fat cells in a meshwork of areolar tissue.
areolar tissue connective tissue made up largely of interlacing fibers.
brown adipose tissue
(brown fat tissue
) brown fat
(bursal equivalent tissue
) a hypothesized lymphoid tissue in nonavian vertebrates including human beings, equivalent to the bursa of Fabricius
in birds: the site of B lymphocyte
maturation. It now appears that B lymphocyte maturation occurs primarily in the bone marrow.
cancellous tissue the spongy tissue of bone.
cartilaginous tissue the substance of cartilage.
chordal tissue the tissue of the notochord.
chromaffin tissue a tissue composed largely of chromaffin cells, well supplied with nerves and vessels; it occurs in the adrenal medulla and also forms the paraganglia of the body.
the tissue that binds together and is the support of the various structures of the body; see also connective tissue
elastic tissue connective tissue made up of yellow elastic fibers, frequently massed into sheets.
endothelial tissue peculiar connective tissue lining serous and lymph spaces.
epithelial tissue a general name for tissues not derived from the mesoderm.
erectile tissue spongy tissue that expands and becomes hard when filled with blood.
fatty tissue connective tissue made of fat cells in a meshwork of areolar tissue.
fibrous tissue the common connective tissue of the body, composed of yellow or white parallel elastic and collagen fibers.
granulation tissue material formed in repair of wounds of soft tissue, consisting of connective tissue cells and ingrowing young vessels; it ultimately forms cicatrix.
gut-associated lymphoid tissue (GALT) lymphoid tissue associated with the gut, including the tonsils, Peyer's patches, lamina propria of the gastrointestinal tract, and appendix.
indifferent tissue undifferentiated embryonic tissue.
interstitial tissue connective tissue between the cellular elements of a structure.
lymphadenoid tissue tissue resembling that of lymph nodes, spleen, bone marrow, tonsils, and lymph vessels.
a latticework of reticular tissue whose interspaces contain lymphocytes
mesenchymal tissue embryonic connective tissue composed of stellate cells and a ground substance of coagulable fluid.
a jellylike connective tissue, such as occurs in the umbilical cord. Called also gelatinous tissue
muscular tissue the substance of muscle.
nerve tissue (nervous tissue) the specialized tissue forming the elements of the nervous system.
osseous tissue the specialized tissue forming the bones.
reticular tissue (reticulated tissue) connective tissue composed predominantly of reticulum cells and reticular fibers.
sclerous t's the cartilaginous, fibrous, and osseous tissues.
skeletal tissue the bony, ligamentous, fibrous, and cartilaginous tissue forming the skeleton and its attachments.
subcutaneous tissue the layer of loose connective tissue directly under the skin.
identification of tissue types for purposes of predicting acceptance or rejection of grafts
. The process and purposes of tissue typing are essentially the same as for blood typing. The major difference lies in the kinds of antigens being evaluated. The acceptance of allografts depends on the hla antigens
(HLA); if the donor and recipient are not HLA identical, the allograft is rejected, sometimes within minutes. The HLA genes are located in the major histocompatibility complex
, a region on the short arm of chromosome 6, and are involved in cell-cell interaction, immune response
, organ transplantation, development of cancer, and susceptibility to disease. There are five genetic loci, designated HLA-A, HLA-B, HLA-C, HLA-D, and HLA-DR. At each locus, there can be any of several different alleles.
Each person inherits one chromosome 6 from the mother and one from the father; that is, each parent transmits to the child one allele for each kind of antigen (A, B, C, D, and DR). If the parents are different at both alleles of a locus, the statistical chance of one sibling being identical to another is one in four (25 per cent), the chance of being identical at one allele only (half-identical) is 50 per cent, and the chance of a total mismatch is 25 per cent.
Techniques for Tissue Typing
. Histocompatibility testing involves several basic methods of assay for HLA differences. The most widely used method uses the polymerase chain reaction
to compare the DNA of the person, organ, or graft being tested with known pieces of the genes encoding MHC antigens. The variability of these regions of the genes determines the tissue type of the subject.Serologic methods
are used to detect serologically defined antigens on the surfaces of cells. In general, HLA-A, -B, and -C determinants are primarily measured by serologic techniques. A second method, involving lymphocyte reactivity in a mixed lymphocyte culture, for determining HLA-D or lymphocyte-defined antigens, is now only rarely used.
Essentially, the serologic method is performed by incubating target lymphocytes (isolated from fresh peripheral blood) with antisera that recognize all known HLA antigens. The cells are spread in a tray with microscopic wells containing various kinds of antisera and are incubated for 30 minutes, followed by an additional 60-minute complement incubation. If the lymphocytes have on their surfaces antigens recognized by the antibodies in the antiserum, the lymphocytes are lysed. A dye is added to show changes in the permeability of the cell membrane and cellular death. The proportion of cells destroyed by lysis indicates the degree of histologic incompatibility. If, for example, the lymphocytes from a person being tested for HLA-A3 are destroyed in a well containing antisera for HLA-A3, the test is positive for this antigen group.
white adipose tissue (yellow adipose tissue) the adipose tissue composing the bulk of the body fat.
tissue (tish'oo) [Fr. tissu, from L. texere, to weave]
A group or collection of similar cells and their intercellular substance that perform a particular function. The four major groups are epithelial, connective, muscular, and nervous tissues.
A form of loose connective tissue consisting of fibroblasts in a matrix of tissue fluid and collagen and elastin fibers. Many white blood cells are present. It is found subcutaneously and beneath the epithelium of all mucous membranes. See: connective tissue
bone tissueOsseous tissue.illustration
bronchus-associated lymphoid tissue Abbreviation: BALT
Lymph nodules that contain clusters of T and B lymphocytes and macrophages within the mucosa of the bronchial wall; a component of the mucosal immune system that defends all mucosal surfaces against pathogens. See: mucosal immune system
brown adipose tissue Abbreviation: BAT
Spongy bone with many marrow cavities. It is present at the ends of long bones and in the interior of most flat bones.
Tissue of the notochord or derived from it. The nucleus pulposus is derived from the notochord.
chromaffin tissueChromaffin system.
Tissue that supports and connects other tissues and parts of the body. Connective tissue has comparatively few cells. Its bulk consists of intercellular substance or matrix, whose nature gives each type of connective tissue its particular properties. The vascular supply varies: cartilage, none; fibrous, poor; adipose, good; and bone, abundant. Connective tissue includes the following types: areolar, adipose, fibrous, elastic, reticular, cartilage, and bone. Blood may also be considered a connective tissue. illustration
A form of connective tissue in which yellow elastic fibers predominate. It is found in certain ligaments, the walls of blood vessels, esp. the larger arteries, and around the alveoli of the lungs.
Any tissue that arises from the fertilization of an ovum and has not become differentiated or specialized.
Spongy tissue, the spaces of which fill with blood, causing it to harden and expand. It is found in the penis, clitoris, and nipples.
Connective tissue consisting principally of collagen fibers. Also called white fibrous or dense connective tissue; may be regular (parallel fibers) or irregular.
Tissue from which gelatin may be obtained by treating it with hot water.
A group of epithelial cells capable of producing secretions.
The newly formed vascular and connective tissue produced in the early stages of wound healing.
In dentistry, the term used to denote any of the three calcified tissue components of the tooth: enamel, dentin, and cementum.
Tissues that are identical in structure.
Tissue composed of undifferentiated cells as in embryonic tissue.
Connective tissue that forms a network with the cellular portions of an organ.
Aggregates of lymphatic tissue found in the spleen and lymph nodes.
Collections of lymphocytes in all stages of development found in the spleen, thymus, lymph nodes, lymph nodules of the digestive tract (tonsils, Peyer's patches), and the respiratory, urinary, and reproductive tracts.
The embryonic mesenchyme.
mucosa-associated lymphoid tissue Abbreviation: MALT
Aggregates of T and B lymphocytes found in all mucous membranes, a line of defense against infection. Examples include Peyer's patches in the small intestine and lymph nodules in the colon, trachea, and bronchi. MALT contains CD4+ and CD8+ T cells and activated B cells and may occasionally undergo malignant transformation into lymphomas. See: mucosal immune system
The jellylike connective tissue of the umbilical cord.
The bone marrow in which most blood cells are formed.
The neurons and neuroglia of the nervous system. See: neuron
Bone, a connective tissue with a matrix of calcium phosphate and calcium carbonate surrounding osteocytes Synonym: bone tissue See: bone
A type of connective tissue consisting of delicate fibers forming interlacing networks. Fibers stain selectively with silver stains and are called argyrophil fibers. Reticular tissue supports blood cells in lymph nodes, bone marrow, and the spleen.
Firm connective tissue such as bone and cartilage.
Any noncalcified tissue in the body. This term is especially used in relation to muscles, tendons, ligaments, skin, fat, and other connective tissues that are occasionally the source of pain when they are injured. Unlike bones or joints, which can be fractured or dislocated, soft tissues are bruised or inflamed by trauma. In surgery, soft tissues are dissected. By contrast, components of the (hard) bony skeleton are sawed, chiselled, or drilled. Soft tissues include all types of tissue except bone, i.e., all epithelial, muscle, and nerve tissue, as well as connective tissue excluding bone.
The highly vascular splenic pulp.
subcutaneous tissueSuperficial fascia.