口腔生理学术语(T)

    Template - an outline form which can be used to make many identical copies without being used itself. Metal templates can be used placed over a piece of clothing material, which is then cut according to the shape of the template. Many pieces can be made from the same template, and they will all be the right shape for that part of the garment. Molecular templates can guide the formation of crystals by providing a shape which is characteristic of, for example anapatite crystal. The role of templates in crystal formation is calledepitaxy.

    Temporomandibular joint - the joint between the condyle of the mandible and the glenoid fossa of the temporal bone. The joint is divided into an upper and lower compartment by a fibrous disc and surrounded by a capsule.

    Tenascin - an adhesive molecule of connective tissue related to fibronectin andlaminin.

    Thalamus - the major co-ordinating centre or sensory information in the brain.

    Threshold - the minimum level of a signal(sound. pressure, pain) which is detectable.

    Thrombin - the final chain in the series of blood clotting forms fibrin from fibrinogen. Thrombin is formed from prothrombin by a prothrombin activator, itself the end of a series of reactions. This cascade of events may begin two ways. One, is the release of tissue factors from damaged vessels. The other, is the activation of factors in blood platelets which are altered by coming into contact with collagen or an artificial surface.

    Thromboxanes - concerned with platelet clotting and a member of the eicosanoid family of hormones.

    ical - in a local area. e.g application of medication to the affected part only.

    Trabecula-bone -a description of the radiographic appearance of spongy bone. Radiographs provide an unusual opportunity to see condensations within spongy bone. These condensations form lines, or beams with are orientated so as to give the best support to loads tending to crush or fracture the bone.( the Latin word for a wooden beam was trabes, a small beam was a trabecula)

    Transcription- a process which leads to the copying of a gene's code, from a section of DNA, onto a strand of messenger RNA and which eventually leads to the synthesis of the peptide or protein which that gene codes for.

    Transforming growth factor- TGF a superfamily of cytokines secreted by a variety of cells (monocytes, T cells, platelets, fibroblasts). The family include bone morphogenic proteins, which stimulate angiogenesis, fibroblast proliferation and inhibit T cell proliferation.

    Tropocollagen - the precursor to the collagen molecule secreted by the cell. The removal of terminal peptides on the tropocollagen allows each molecule to join end to end with another to make a collagen fibril.

    Tubule - a small tube leading into a duct,or as in dentinal tubules.

    Turnover - the replacement of cells by mitosis which keeps pace with cell loss, as in epithelia and blood cells. Also refers to the continual replacement of connective tissues like bone and fibrous tissue.