Horse Health Glossary

Not sure what that veterinary word means? Look it up below!

Reprinted with permission from the University of California, Davis, The Book of Horses edited by Mordecai Siegal.

T LYMPHOCYTES (T CELLS):
Specialized lymphocytes that mature within the thymus; two important types are cytotoxic T cells and helper T cells.
TACHYCARDIA:
Abnormally fast heart rate.
TACHYPNEA:
Abnormally rapid breathing.
TACHYZOITES:
Actively dividing form of the parasite Toxoplasma gondii found in the tissues of an infected animal.
TAIL-CHEWING:
A stable vice exhibited primarily by yearlings and two-year-olds.
TAPETUM:
The reflective layer in the upper half of the back of the eye.
TAXONOMY:
The classification of organisms into different categories on the basis of their individual physical and biochemical relationships to each other.
TELOGEN:
The phase of hair follicle activity during which the follicle is resting and not producing new hair.
TEMPORAL REGION:
Area of the head in front of the ears and lateral to the forehead.
TENDINITIS:
Inflammation of a tendon or tendon muscle attachment; also spelled tendonitis.
TENDON:
Fibrous tissue that attaches muscle to bone.
TENOSYNOVITIS:
Inflammation of the lining membrane that surrounds the tendon sheath.
TENOTOMY:
Surgical cutting of a tendon.
TERATOGEN:
Any compound or agent that disrupts normal development in utero, producing defects in the developing embryo.
TERATOLOGY:
The study of abnormal development and congenital malformations.
TERATOMA:
Ovarian tumor characterized by the formation of cysts as well as a bizarre combination of different embryonic tissues such as bone, cartilage, teeth, and hair.
TEST CROSS:
A mating between a homozygous recessive and an animal with the phenotype of the dominant allele.
TESTES, TESTICLES:
Paired reproductive organs of the male wherein the spermatozoa (sperm) are produced.
TESTOSTERONE:
The principal male sex hormone, produced in the testes.
TETANOSPASMIN:
The neurotoxin produced in tetanus.
TETANUS:
Acute, often fatal disease caused by a neurotoxin from the bacterium Clostridium tetani, and characterized by violent muscle spasms and contractions, hyperreflexive responses, and "lockjaw" (trismus); horses are highly sensitive to the action of tetanus neurotoxin.
TETANY:
Seizurelike tremors caused most often by a decrease in circulating calcium levels.
TETRALOGY OF FALLOT:
Congenital heart defect characterized by the presence of a ventricular septal defect (VSD) and severe pulmonic stenosis, together with an abnormally positioned aorta and thickening of the right ventricle.
TETRAPLEGIA:
Paralysis of all four limbs.
THALAMUS:
Portion of the brain that serves as a relay center for sensory information coming from the rest of the body, and for nerve impulses concerned with balance and coordination arising from the cerebellum.
THEILER'S DISEASE:
Alternative name for serum hepatitis.
THERIOGENOLOGY:
Study of the physiology and pathology of animal reproduction.
THERMOCAUTERY:
Destruction of tissue using a hot point or instrument.
THORACIC:
Pertaining to the chest.
THORACOCENTESIS:
Procedure in which a sterile hypodermic needle is inserted into the chest cavity in order to remove accumulated air or fluid, or to obtain a sample of fluid or lung tissue for examination.
THORACOLUMBAR:
Pertaining to the upper trunk and back.
THOROUGHPIN:
Stress on the deep digital flexor tendon, with puffiness in the web of the hock.
THROATLATCH:
Area of the throat under which the strap of a bridle or halter passes.
THROMBOCYTOPENIA:
Abnormally decreased numbers of circulating blood platelets.
THROMBOEMBOLISM:
Obstruction of a blood vessel by a clot originating at another site.
THROMBOPHLEBITIS:
Inflammation of a vein, accompanied by the formation of a blood clot.
THROMBOPLASTIN:
A protein essential for blood clotting.
THROMBOSIS:
Formation of a blood clot (thrombus) that results in obstruction of a blood vessel at the site of clot formation; contrasts with embolism, which is a blood-borne clot that lodges at a site distant from its site of formation.
THROMBUS:
A blood clot causing obstruction of a blood vessel at the site of clot formation.
THRUSH:
Degenerative condition of the frog of the foot, characterized by infection and blackening of the affected area; usually occurs in horses housed under unsanitary conditions.
THYMUS:
Lymphoid organ located in the chest that produces hormones (thymopoietin, thymosin) and that regulates the maturation process of specialized lymphocytes known as T cells.
THYROID GLAND:
Endocrine gland located on either side of the trachea that produces hormones (thyroxine, triiodothyronine) important in regulating the body's metabolic rate.
THYROID HORMONE:
Collective name for the two major hormones produced by the thyroid gland, thyroxine (T4) and triiodothyronine (T3).
THYROIDECTOMY:
Removal of all or part of the thyroid gland.
THYROID-STIMULATING HORMONE (TSH):
Hormone elaborated by the pituitary gland that stimulates the thyroid gland to produce the hormones thyroxine (T4) and triiodothyronine (T3).
THYROXINE (T4):
One of two important iodine-containing hormones secreted by the thyroid gland that assist in regulating the cellular metabolic rate of the body.
TITER:
A quantitative measure of the concentration of an antibody or antigen in blood serum; determined in principle by making serial dilutions of serum and identifying the highest dilution at which the antibody or antigen can still be detected.
TOBIANO:
Dominantly inherited equine coat-color pattern, expressed as a white base coat with colored patches on the body. The legs are usually white, and white normally crosses the back. The colored areas are regular, usually oval or round. The head is colored as are the flanks.
TOCOPHEROLS:
General term for vitamin E.
TOLERANCE:
The normal state whereby the immune system remains nonreactive or "tolerant" to the body's own cells.
TORSION:
A twisting.
TOTAL DIGESTIBLE NUTRIENTS (TDN):
For a feed, the sum of the digestible carbohydrate, protein, fat, and fiber; also called digestible energy (DE).
TOVERO:
Equine coat-color pattern with characteristics of both tobiano and overo.
TOXEMIA:
Presence of toxins in the blood, accompanied by related signs of disease.
TOXOPLASMOSIS:
A protozoan disease caused by Toxoplasma gondii.
TRACE MINERALS:
Minerals that are required in the diet only in very minute amounts; for horses these usually include copper, iodine, iron, manganese, selenium, and zinc.
TRACHEA:
Cartilage-lined tubular airway that descends from the larynx into the chest and branches at its lower end into two bronchi that enter the lungs; it conducts air between the upper nasal passages and the lungs; colloquially known as the windpipe.
TRACHEITIS:
Inflammation of the trachea.
TRACHEOSTOMY:
Surgically created opening through the skin into the trachea, to allow for insertion of a tube for breathing and to clear airway obstructions.
TRANSMAMMARY:
Through the milk or colostrum.
TRANSPLACENTAL(LY):
By way of the placenta; across the placenta.
TRANSPORT HOST:
An animal in which part of the immature phase of a parasite's life cycle is spent, but no development occurs.
TRANSTRACHEAL WASH:
Flushing of material from the trachea and bronchi for diagnostic purposes, by needle puncture and aspiration through the skin and tracheal wall.
TREMATODES:
Flukes.
TRICHIASIS:
Condition wherein facial hair or eyelashes arising from normal sites are misdirected and contact the cornea or conjunctiva.
TRICHINOSIS:
Serious, occasionally fatal food-borne disease of humans caused by a parasitic worm, Trichinella spiralis, whose larval forms are found in muscle tissue. When the (raw or undercooked) muscle is eaten, the larvae are liberated and mature in the small intestine, where the adults reproduce and produce offspring.
TRICUSPID VALVE:
The atrioventricular valve on the right side of the heart.
TRIGLYCERIDES:
A component of fat, consisting of fatty acids linked to glycerol.
TRIIODOTHYRONINE (T3):
An important iodine-containing hormone secreted by the thyroid gland that assists in regulating the cellular metabolic rate of the body; much more powerful than its companion hormone thyroxine, it is considered to be the active form of thyroid hormone in tissue.
TRISMUS:
"Lockjaw," caused by spasm of the chewing muscles; seen in tetanus..
TROCHANTERIC BURSITIS:
Inflammation of the bursa that lies beneath the tendon of the middle gluteal muscle as it passes over the point of the hip.
TROPHOZOITES:
Motile feeding forms of the parasite Giardia; they multiply in the small intestine by means of binary fission.
TRUNCUS ARTERIOSUS:
Congenital heart defect consisting of a ventricular septal defect (VSD) and a single large arterial trunk exiting both ventricles.
TUBERCULOSIS:
An ancient disease of humans and animals, caused by bacteria belonging to the genus Mycobacterium. Most infections in horses are caused by Mycobacterium bovis and are characterized by fever, respiratory difficulty, inappetence, weight loss, and lymph node enlargement.
TUMOR:
A large nodule, or obvious cancerous mass.
TURGOR:
Skin elasticity.
TURNER'S SYNDROME:
The most common chromosomal abnormality of mares, characterized by a missing X chromosome; also called 63,X gonadal dysgenesis.
TYING-UP:
A mild form of azoturia.
TYMPANIC MEMBRANE:
Eardrum.
TYMPANY:
Distension.
TYZZER'S DISEASE:
An extremely rare and highly fatal liver disease of foals caused by a spore-forming bacterium, Bacillus piliformis.

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