| IRV | inferior radicular vein; inspiratory reserve volume; inverse ratio ventilation |
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| ITA | inferior temporal artery; internal thoracic artery; International Tuberculosis Association |
| ITQ | inferior temporal quadrant |
| ITV | inferior temporal vein |
| IVC | inferior vena cava; inspiratory vital capacity; integrated vector control; intravascular coagulation... |
| cornua of thyroid cartilage | See: inferior horn of thyroid cartilage, superior horn of thyroid cartilage. Cornu uteri, the portion of the uterus to which the intramural section of the uterine tube enters on either the right or left. Synonym: uterine horn, horn of uterus. (05 Mar 2000) |
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| posterior branch of superior thyroid artery | <anatomy, artery> Branch of superior thyroid artery which descends to supply the apical portion of the ipsilateral lobe of the thyroid, continuing along the posterior border of the gland to anastomose with the inferior thyroid artery. Synonym: ramus posterior arteriae thyroideae superioris. (05 Mar 2000) |
| hormone, thyroid | Chemical substance made by the thyroid gland which is located in the front of the neck. The thyroid gland uses iodine to make thyroid hormones. The two most important thyroid hormones are thyroxine (t4) and triiodothyronine (t3). (12 Dec 1998) |
| hormone, thyroid stimulating | A hormone produced by the pituitary gland (at the base of the brain) that promotes the growth of the thyroid gland (in the neck) and stimulates it to produce its thyroid hormones. Normally, the rate of thyroid hormone production is controlled by the pituitary. When there are insufficient thyroid hormones in the body for normal functioning of the cells, the pituitary releases tsh. Tsh in turn stimulates the thyroid gland to produce more thyroid hormones. In contrast, when there is excessive amount of thyroid hormones, the pituitary gland stops producing tsh. The tsh level then falls and thyroid hormone production is reduced. This mechanism maintains a relatively constant level of thyroid hormones circulating in the blood. This phenomenon is analogous to a thermostat used for temperature regulation in a room: when the temperature rises, the thermostat shuts the heater off and the room temperature falls back to normal. High levels of thyroid hormones cause the tsh level to fall, resulting in no further stimulation of the thyroid gland. In hyperthyroidism, there are continuously elevated levels of the thyroid hormones. Tsh is also known as thyrotropin. (12 Dec 1998) |
| horns of thyroid cartilage | See: inferior horn of thyroid cartilage, superior horn of thyroid cartilage. (05 Mar 2000) |
| hot thyroid nodule | <radiology> Almost always hyperfunctioning adenoma, vast majority benign, up to 50% are autonomous see also: thyroid carcinoma, cold thyroid nodule (12 Dec 1998) |
| pyramidal lobe of thyroid gland | <anatomy> An inconstant narrow lobe of the thyroid gland that arises from the upper border of the isthmus and extends upward, sometimes as far as the hyoid bone; it marks the point of continuity with the thyroglossal duct. Synonym: lobus pyramidalis glandulae thyroideae, Lallouette's pyramid, Morgagni's appendix, pyramid of thyroid. (05 Mar 2000) |
| pyramid of thyroid | <anatomy> An inconstant narrow lobe of the thyroid gland that arises from the upper border of the isthmus and extends upward, sometimes as far as the hyoid bone; it marks the point of continuity with the thyroglossal duct. Synonym: lobus pyramidalis glandulae thyroideae, Lallouette's pyramid, Morgagni's appendix, pyramid of thyroid. (05 Mar 2000) |
| sheath of thyroid gland | Covering of the thyroid gland external to its capsule formed by a splitting of the pretracheal layer of deep cervical fascia at the gland's posterior border; the anterior lamina covers the gland anterolaterally, attaching to the arch of the cricoid cartilage superior to the isthmus of the gland (causing it to move with the trachea during elevation/depression of the larynx); the posterior lamina passes posterior to the oesophagus to blend with the buccopharyngeal fascia; inferiorly, the sheath extends along the inferior thyroid veins to open into the superior mediastinum (hence, expansion of the thyroid, as by goiter, can take this direction). (05 Mar 2000) |
| sternocleidomastoid branch of superior thyroid artery | <anatomy, artery> Branch of superior thyroid artery to sternocleidomastoid muscle. Synonym: ramus sternocleidomastoideus arteriae thyroideae superioris. (05 Mar 2000) |
| stroma of thyroid gland | The connective tissue that supports the lobules and follicles of the thyroid gland. Synonym: stroma glandulae thyroideae. (05 Mar 2000) |
| superior horn of thyroid cartilage | One of the pair of upward prolongations from the thyroid cartilage to which the lateral hyothyroid ligament attaches. Synonym: cornu superius cartilaginis thyroideae. (05 Mar 2000) |
| superior thyroid artery | <anatomy, artery> Origin, external carotid; branches, infrahyoid, superior laryngeal, sternocleidomastoid, cricothyroid, and two terminal branches. Synonym: arteria thyroidea superior. (05 Mar 2000) |
| superior thyroid plexus | An autonomic plexus on the artery of the same name, derived from the external carotid plexus. Synonym: plexus thyroideus superior. (05 Mar 2000) |
| superior thyroid tubercle | A blunt projection on the lamina of the thyroid cartilage on either side at the superior end of the oblique line. Synonym: tuberculum thyroideum superius. (05 Mar 2000) |