Medical Terminology Glossary
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tachycardia - a rapid heartbeat or pulse rate

tactile - pertaining to the sense of touch

taenia coli - one of the three flat bands of thickened, longitudinal muscles running the length of the large intestine

tarsus - a collective term for the seven bones of the ankle

Tay-Sachs disease - inherited, progressive neuronal degeneration of the central nervous system due to a deficient lysosomal enzyme; it causes excessive accumulations of a lipid called ganglioside

tectorial membrane - gelatinous membrane projecting over, and in contact with, the hair cells of the spiral organ (organ of Corti) in the cochlear duct

telophase - final stage of mitosis, in which the daughter nuclei become established

tendon - a white fibrous cord of dense, regularly arranged connective tissue that attaches muscle to bone

tenosynovitis - inflammation of a tendon sheath and synovial membrane at a joint

tentorium cerebelli - a transverse shelf of dura mater; forms a partition between the occipital lobe of the cerebral hemisphere and the cerebellum; covers the cerebellum

teratogen - agent or factor that causes physical defects in developing embryos

terminal ganglion - cluster of postganglionic parasympathetic neuronal cell bodies, either lying very close to the visceral effectors or located within the walls of the visceral effectors supplied by those postganglionic fibers

testis - a male gonad; it produces sperm and the hormones testosterone and inhibin; also called a testicle; plural, testes

testosterone - male sex hormone (androgen) secreted by interstitial endocrinocytes (cells of Leydig) of mature testes; controls growth and development of male sex organs

tetanus - infectious disease caused by the toxin of Clostridium tetani and characterized by tonic muscle spasms, exaggerated reflexes, lockjaw, and arching of the back; a smooth, sustained contraction produced by a series of very rapid stimuli to a muscle

tetany - a nervous condition caused by hypoparathyroidism & characterized by intermittent or continuous tonic muscle contractions of the extremities

tetralogy of Fallot - combination of congenital heart defects: 1) constricted pulmonary semilunar valve, 2) interventricular septal opening, 3) emergence of aorta from both ventricles (instead of from left only), and 4) enlarged right ventricle

thalamus - large, oval structure located above the midbrain and consisting of two masses of gray matter covered by a thin layer of white matter

thalassemia - group of hereditary hemolytic anemias

thallium imaging - diagnostic procedure used to evaluate: blood flow through coronary arteries, cardiac disorders, & effectiveness of drug therapy; thallium concentrates in healthy myocardial tissue

therapy - the treatment of a disease or disorder

thermoreceptor - any receptor that detects changes in temperature

thoracic cavity - superior component of the ventral body cavity; it contains two pleural cavities, the mediastinum, and the pericardial cavity

thoracolumbar outflow - fibers of the sympathetic preganglionic neurons; they have their cell bodies in the lateral gray columns of thoracic and upper lumbar segments of the spinal cord

thorax - the chest; the upper part of the trunk between the neck and the abdomen

thrombin - the active enzyme formed from prothrombin; acts to convert fibrinogen to fibrin

thrombocyte - a fragment of cytoplasm; is enclosed in a cell membrane and lacks a nucleus; found in the circulating blood; plays a role in blood clotting; also called a platelet

thrombolytic agent - chemical injected into the blood to dissolve clots and restore circulation through direct or indirect activation of plasminogen; examples include tissue plasminogen activator (t-PA), streptokinase, & urokinase

thrombophlebitis - a disorder in which inflammation of the wall of a vein is followed by blood clot (thrombus) formation

thrombosis - formation of a clot in an unbroken blood vessel, usually a vein

thymectomy - surgical removal of the thymus gland

thymus - a bilobed organ, located in the upper mediastinum posterior to the sternum and between the lungs that plays an essential role in the immune mechanism of the body

thyroglobulin (TGB) - a large glycoprotein molecule, secreted by follicle cells of the thyroid gland, in which iodine and tyrosine are combined to form thyroid hormones

thyroid cartilage - largest single cartilage of the larynx, consisting of two fused plates that form its anterior wall; also called the Adam's apple

thyroxine (T4) - a hormone secreted by the thyroid gland; it regulates growth and development, organic metabolism, and the activity of the nervous system

tinnitus - ringing, roaring, or clicking in the ears

tonometry - a test used to measure the intraocular pressure as a screen for glaucoma

tonsil - a multiple aggregation of large lymphatic nodules, embedded in mucous membrane

topical - applied to a surface, rather than ingested or injected

torpor - state of lethargy and sluggishness preceding stupor, which precedes semicoma, which precedes coma

toxic - pertaining to poison; poisonous

trabecula - an irregular latticework of thin plate of spongy bone; fibrous cord of connective tissue serving as supporting fiber by forming a septum that extends into an organ from its wall or capsule; plural, trabeculae

trabeculae carneae - ridges and folds in the myocardium of the ventricles

trachea - a tubular air passageway, extending from the larynx to the fifth thoracic vertebra; also called the windpipe

tracheostomy - creation of an opening into the trachea through the neck (below the cricoid cartilage), with insertion of a tube to facilitate passage of air or evacuation of secretions

trachoma - chronic infectious disease of the conjunctiva and cornea of the eye, caused by Chlamydia trachomatis

transfusion - a transfer of whole blood, blood components, or bone marrow, directly into the bloodstream

transient ischemic attack - an episode of temporary, focal, nonconvulsive cerebral dysfunction, caused by interference with the blood supply to the brain

transplantation - the replacement of injured or diseased tissues with natural ones from another part or another individual

transverse colon - portion of the large intestine extending across the abdomen from right colic (hepatic) flexure to left colic (splenic) flexure

trauma - an injury, either a physical wound or a psychic disorder, caused by an external agent or force, such as a physical blow or emotional shock; the agent or force that causes the injury

tremor - rhythmic, involuntary, purposeless contraction of opposing muscle groups

treppe - the gradual increase in the amount of contraction of a muscle caused by rapid, repeated stimuli of the same strength

triad - a complex of three LETTERs in a muscle fiber (cell), composed of a transverse tubule and the segments of sarcoplasmic reticulum on both sides of it

tricuspid valve - the atrioventricular (AV) valve on the right side of the heart

trigeminal neuralgia - pain in one or more of the branches of the trigeminal (V) nerve; also called tic doloureux

triglyceride - a lipid compound formed from one molecule of glycerol and three molecules of fatty acids; used for concentrated energy storage; prime component of adipose (fat) tissue; also called a neutral fat

trigone - triangular area at the base of the urinary bladder

triiodothyronine (T3) - a hormone produced by the thyroid gland; it regulates growth and development, organic metabolism, and the activity of the nervous system

trochlea - a pulley-like surface

trophoblast - the outer covering of cells of the blastocyst

tropic hormone - a hormone whose target is another endocrine gland

tubal ligation - a sterilization procedure in which the uterine (Fallopian) tubes are tied and cut

tuberculosis - infection of the lungs and pleurae caused by Mycobacterium tuberculosis

tumor - a growth of excess tissue due to an unusually rapid division of cells

tunica albuginea - the dense layer of white fibrous tissue covering a testis or deep to the surface of an ovary

tympanic antrum - air space in the posterior wall of the middle ear; it leads into the mastoid air cells or sinus