1. SYN: trigonum. 2. The first three dominant cusps (protocone, paracone, and metacone), taken collectively, of an upper molar tooth. [L. trigonum, fr. G. trigonon, triangle]
- t. of auditory nerve the slight prominence of the floor of the lateral recess of the fourth ventricle, corresponding to the underlying cochlear and vestibular nuclei. SYN: acoustic tubercle, trigonum nervi acustici.
- t. of bladder [TA] a triangular smooth area at the base of the bladder between the openings of the two ureters and that of the urethra. SYN: trigonum vesicae [TA], Lieutaud body, Lieutaud triangle, Lieutaud t., vesical triangle.
- collateral t. [TA] a triangular prominence of the floor of the lateral ventricle at the transition between occipital and temporal horn, continuous rostrally with the collateral eminence and, like the latter, caused by the deep penetration of the collateral sulcus from the ventral surface of the temporal lobe. SYN: trigonum collaterale [TA], t. of lateral ventricle, trigonum ventriculi, ventricular t..
- deltoideopectoral t. SYN: infraclavicular fossa.
- habenular t. [TA] a small triangular area on the dorsomedial surface of the thalamus at the caudal end of the medullary stria, corresponding to the underlying habenula. SYN: trigonum habenulae [TA], t. of habenula.
- hypoglossal t. [TA] a slight elevation in the floor of the inferior recess of the fourth ventricle, beneath which is the nucleus of origin of the twelfth cranial nerve. SYN: trigonum nervi hypoglossi [TA], t. of hypoglossal nerve, eminentia hypoglossi, hypoglossal eminence, trigonum hypoglossi, tuberculum hypoglossi.
- t. of lateral lemniscus [TA] a triangular area on the lateral surface of the caudal half of the mesencephalon, bordered caudally by the slight prominence of the lateral lemniscus, dorsally by the base of the inferior colliculus and the brachium of the superior colliculus, and ventrally by the crus cerebri. SYN: lemniscal t., Reil triangle, triangle of fillet, t. of fillet.
- left fibrous t. (of heart) the part of the fibrous skeleton of the heart located in the interval between the left side of the left atrioventricular ring and the aortic ring. SYN: trigonum fibrosum sinistrum.
- olfactory t. [TA] a grayish triangular area corresponding to the attachment of the olfactory peduncle (“olfactory nerve” or olfactory tract) to the base of the brain, at the anterior border of the anterior perforated substance. SYN: trigonum olfactorium [TA].
- right fibrous t. (of heart) [TA] part of the fibrous skeleton of the heart located between the aortic fibrous ring and rings surrounding the right and left atrioventricular ostia. SYN: trigonum fibrosum dextrum.
- vagal (nerve) t. [TA] a prominence in the floor of the inferior fovea of the fourth ventricle that overlies the dorsal motor nucleus of the vagus. SYN: trigonum nervi vagi [TA], t. of vagus nerve, trigonum vagale, ala cinerea, ashen wing, gray wing, vagi eminentia.
- ventricular t. SYN: collateral t..
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tri·gone 'trī-.gōn also tri·gon -.gän n a triangular body part specif a smooth triangular area on the inner surface of the bladder limited by the apertures of the ureters and urethra
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n.
a triangular region or tissue, such as the triangular region of the wall of the bladder that lies between the openings of the two ureters and the urethra.
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tri·gone (triґgōn) 1. triangle. 2. the first three cusps of an upper molar tooth; see hypocone, paracone, and protocone.Medical dictionary. 2011.