| crural triangle | An area of predilection for the petechial initial rash of smallpox; it occupies the lower abdominal, inguinal, and genital regions and the inner aspects of the thighs, the base of the triangle traversing the umbilicus. (05 Mar 2000) |
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| posterior triangle of neck | The region of the neck bounded by the sternocleidomastoid muscle, the trapezius muscle, and the upper border of the clavicle, including the omoclavicular triangle. Synonym: lateral region of neck, regio cervicalis lateralis, trigonum cervicale posterius. (05 Mar 2000) |
| sacral triangle | The surface area over the sacrum. (05 Mar 2000) |
| Scarpa's 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) |
| Hesselbach's triangle | The triangular area in the lower abdominal wall bounded by the inguinal ligament below, the border of the rectus abdominis medially and the inferior epigastric vessels (lateral umbilical fold) laterally. It is the site of direct inguinal hernia. Synonym: trigonum inguinale, Hesselbach's triangle, inguinal trigone. (05 Mar 2000) |
| pubourethral triangle | A triangle in the perineum bounded by the transversus perinei, the ischiocavernosus, and the bulbocavernosus muscles. (05 Mar 2000) |
| sternocostal triangle | A muscular defect in the diaphragm between the costal and the sternal portions. Synonym: Larrey's cleft, sternocostal triangle. (05 Mar 2000) |
| subclavian 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) |
| subinguinal 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) |
| submandibular triangle | The triangle of the neck bounded by the mandible and the two bellies of the digastric muscle; it contains the submandibular gland. Synonym: trigonum submandibulare, digastric triangle, submaxillary triangle. (05 Mar 2000) |
| submaxillary triangle | The triangle of the neck bounded by the mandible and the two bellies of the digastric muscle; it contains the submandibular gland. Synonym: trigonum submandibulare, digastric triangle, submaxillary triangle. (05 Mar 2000) |
| submental triangle | A triangle bounded by the anterior belly of the digastric muscles, and the hyoid bone; the mylohyoid muscle forms its floor. Synonym: trigonum submentale. (05 Mar 2000) |
| suboccipital triangle | A deep triangle bounded by the obliquus capitis inferior, the obliquus capitis superior, and the rectus capitis posterior major muscles. (05 Mar 2000) |
| superior carotid triangle | A space bounded by the superior belly of the omohyoid muscle, anterior border of the sternocleidomastoid, and posterior belly of the digastric; it contains the bifurcation of the common carotid artery. Synonym: trigonum caroticum, fossa carotica, Gerdy's hyoid fossa, Malgaigne's fossa, Malgaigne's triangle, superior carotid triangle. (05 Mar 2000) |
| superior triangle sign | In chest radiology, widening of the superior mediastinum, usually on the right, associated with collapse of the lower lobe producing traction on the mediastinal pleura. (05 Mar 2000) |