| 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) |
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| 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 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) |
| supraclavicular 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) |
| suprameatal triangle | A triangle formed by the root of the zygomatic arch, the posterior wall of the bony external acoustic meatus, and an imaginary line connecting the extremities of the first two lines; used as a guide in mastoid operations. Synonym: Macewen's triangle. (05 Mar 2000) |
| deltoideopectoral triangle | A triangular depression bounded by the clavicle and the adjacent borders of the deltoid and pectoralis major muscles. Synonym: fossa infraclavicularis, deltoideopectoral triangle, deltoideopectoral trigone, infraclavicular triangle, Mohrenheim's fossa, Mohrenheim's space, regio infraclavicularis, trigonum deltoideopectorale. (05 Mar 2000) |
| digastric 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) |
| iliofemoral triangle | In fracture of the neck of the femur to determine upward displacement of the trochanter, lines are drawn on the body to form a triangle: line a is drawn around the body at the level of the anterior superior iliac spines; line b, perpendicular to line a, is drawn to the great trochanter of the femur; line c is drawn from the trochanter to the iliac spine; upward displacement is measured along line b. Synonym: iliofemoral triangle. (05 Mar 2000) |