| accessory thyroid gland | An isolated mass, or one of several such masses, of thyroid tissue, sometimes present in the side of the neck, or just above the hyoid bone (suprahyoid accessory thyroid gland), or even as low as the arch of the aorta. Synonym: glandula thyroidea accessoria, accessory thyroid, prehyoid gland, suprahyoid gland, thyroidea accessoria, thyroidea ima, Wolfler's gland. (05 Mar 2000) |
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| accessory tragus | Small nodules present at birth, anterior to the tragus, derived from first branchial arch remnants and often containing central cartilage. (05 Mar 2000) |
| accessory tubercle | A small apophysis at the posterior part of the base of the transverse process of each of the lumbar vertebrae. Synonym: processus accessorius, accessory tubercle. (05 Mar 2000) |
| accessory vertebral vein | <anatomy, vein> A vein that accompanies the vertebral vein but passes through the foramen of the transverse process of the seventh cervical vertebra and opens independently into the brachiocephalic vein. Synonym: vena vertebralis accessoria. (05 Mar 2000) |
| accessory visual apparatus | The eyelids, with lashes and eyebrows, lacrimal apparatus, conjunctival sac, and extrinsic muscles of the eyeball. Synonym: organa oculi accessoria, accessory organs, accessory visual apparatus, adnexa oculi, appendages of eye. (05 Mar 2000) |
| accessory volar ligaments | The fibrocartilaginous plates, one located on the anterior aspect of each metacarpophalangeal and interphalangeal joint, that are firmly attached to the bases of the phalanges and the heads of the next proximal bones; they are grooved to accommodate the long flexor tendons. Synonym: ligamenta palmaria, accessory volar ligaments. (05 Mar 2000) |
| Gantzer's accessory bundle | <anatomy> An accessory muscle extending from the superficial flexor of the digits to the deep flexor of the digits. (05 Mar 2000) |
| medial accessory olivary nucleus | A detached part of the olivary nucleus medial to the latter's main body, against the lateral side of the medial lemniscus and pyramidal tract. Synonym: nucleus olivaris accessorius medialis. (05 Mar 2000) |
| placenta, accessory | An extra placenta separate from the main placenta. Also called a succenturiate or supernumerary placenta. Placenta accreta: the abnormal adherence of the chorionic villi to the myometrium. The vascular processes of the chorion (a foetal membrane that enters into the formation of the placenta) grow directly in the myometrium (the muscular portion of the uterus). Normally there is tissue intervening between the chorionic villi and the myometrium. Here there is not. The word accreta comes from the latin accretio from ad meaning to or toward + crescere meaning to grow. Placenta accreta can progress to placenta percreta. (12 Dec 1998) |
| dorsal accessory olivary nucleus | A detached part of the olivary nucleus dorsal to the latter's main body. Synonym: nucleus olivaris accessorius dorsalis. (05 Mar 2000) |
| inferior accessory fissure | The fissure that commonly separates the medial basal segment of the right lower lobe of the lung from the other basal segments, seen as an oblique line near the right heart border on chest radiographs. (05 Mar 2000) |
| abducens nerve | <anatomy, nerve> The 6th cranial nerve. The abducens nerve originates in the abducens nucleus of the pons and sends motor fibres to the lateral rectus muscles of the eye. Damage to the nerve or its nucleus disrupts horizontal eye movement control. (12 Dec 1998) |
| abducent nerve | <anatomy> The abducent nerve enervates a muscle which moves the eyeball. Lesions of the sixth cranial nerve result in deviation of the eyeball outward and double vision. Synonym: cranial nerve VI. (27 Sep 1997) |
| accommodation of nerve | <anatomy, nerve> The property of a nerve by which it adjusts to a slowly increasing strength of stimulus, so that its threshold of excitation is greater than it would be were the stimulus strength to have risen more rapidly. (05 Mar 2000) |
| accompanying vein of hypoglossal nerve | Runs with the hypoglossal nerve below and lateral to the hyoglossus muscle, emptying usually into the lingual vein. Synonym: accompanying vein of hypoglossal nerve. (05 Mar 2000) |