| interscalene triangle | Triangular gap bounded by the scalenus anterior and scalenus medius muscles and the first rib to which the muscles attach; the hiatus provides passage for the subclavian artery and the roots of the brachial plexus. Compression of the structures passing through the hiatus by any means is manifest as "thoracic outlet syndrome." Synonym: interscalene triangle. (05 Mar 2000) |
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| occipital triangle | A triangle of the neck bounded by the trapezius, the sternocleidomastoid, and the omohyoid muscles. See: inferior occipital triangle. (05 Mar 2000) |
| omoclavicular triangle | The triangle bounded by the clavicle, the omohyoid muscle, and the sternocleidomastoid muscle; it contains the subclavian artery and vein. Synonym: fossa supraclavicularis major, trigonum omoclaviculare, greater supraclavicular fossa, omoclavicular triangle, subclavian triangle. (05 Mar 2000) |
| omotracheal triangle | The triangle bounded by the sternocleidomastoid muscle, the superior belly of the omohyoid muscle, and the anterior midline of the neck; the infrahyoid muscles occupy most of it. Synonym: trigonum musculare, trigonum omotracheale, inferior carotid triangle, omotracheal triangle, tracheal triangle. (05 Mar 2000) |
| Einthoven's triangle | An imaginary equilateral triangle with the heart at its centre, its equal sides representing the three standard limb leads of the electrocardiogram. (05 Mar 2000) |
| Elaut's triangle | Triangle formed by the iliac arteries and the promontory of the sacrum. (05 Mar 2000) |
| tracheal triangle | The triangle bounded by the sternocleidomastoid muscle, the superior belly of the omohyoid muscle, and the anterior midline of the neck; the infrahyoid muscles occupy most of it. Synonym: trigonum musculare, trigonum omotracheale, inferior carotid triangle, omotracheal triangle, tracheal triangle. (05 Mar 2000) |
| Tweed triangle | A triangle defined by facial and dental landmarks on a lateral cephalometric film, using the Frankfort horizontal plane as a base and intended for use as a guide in the evaluation and planning of orthodontic treatment. (05 Mar 2000) |
| facial triangle | A triangle formed by lines connecting the basion, the prosthion, and the nasion. (05 Mar 2000) |
| Farabeuf's triangle | The triangle formed by the internal jugular and facial veins and the hypoglossal nerve. (05 Mar 2000) |
| umbilicomammillary triangle | A triangle with its apex at the umbilicus and its base at the line joining the nipples. (05 Mar 2000) |
| Killian's triangle | <anatomy> The triangular-shaped area of the cervical oesophagus bordered by the oblique fibres of the inferior constrictor muscle of the pharynx and the transverse fibres of the cricopharyngeus muscle through which Zenker's diverticulum occurs, and the A-V nodal triangle between the coronary sinus orifice and the ventricular crest. Synonym: laimer triangle. (05 Mar 2000) |
| femoral triangle | A triangular space at the upper part of the thigh, bounded by the sartorius and adductor longus muscles and the inguinal ligament, with a floor formed laterally by the iliopsoas muscle and medially by the pectineus muscle; the branches of the femoral nerve are distributed within the femoral triangle; it is bisected by the femoral vessels, which enter the adductor canal at its apex. Synonym: trigonum femorale, fossa scarpae major, Scarpa's triangle, subinguinal triangle. (05 Mar 2000) |
| Koch's triangle | A triangular area of the wall of the right atrium of the heart, that marks the situation of the atrioventricular node. (05 Mar 2000) |
| urogenital triangle | The anterior portion of the perineal region containing the openings of the urethra and vagina in the female and the urethra and root structures of the penis in the male. Synonym: regio urogenitalis, urogenital region. (05 Mar 2000) |