| Grocco's triangle | A triangular patch of dullness at the base of the chest alongside the spinal column, on the side opposite a pleural effusion. Synonym: paravertebral triangle. (05 Mar 2000) |
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| Grynfeltt's triangle | A triangular space bounded above by the end of the last rib and the serratus posterior inferior muscle, anteriorly by the internal oblique, and posteriorly by the quadratus lumborum; lumbar hernia occurs in this space. Synonym: Lesshaft's triangle. (05 Mar 2000) |
| Petit's lumbar triangle | An area in the posterior abdominal wall bounded by the edges of the latissimus dorsi and external oblique muscles and the iliac crest; herniations occasionally occur here. Synonym: trigonum lumbale, Petit's lumbar triangle. (05 Mar 2000) |
| Philippe's triangle | See: semilunar fasciculus. (05 Mar 2000) |
| Ward's triangle | An area of diminished density in the trabecular pattern of the neck of the femur evident by X-ray as well as by direct inspection. (05 Mar 2000) |
| Weber's triangle | On the sole of the foot, an area indicated by the heads of the first and fifth metatarsal bone and the centre of the plantar surface of the heel. (05 Mar 2000) |
| Pirogoff's triangle | A triangle formed by the intermediate tendon of the digastric muscle, the posterior border of the mylohyoid muscle, and the hypoglossal nerve. (05 Mar 2000) |
| colour triangle | A graph on which chromaticity coordinates are plotted. (05 Mar 2000) |
| Wilde's triangle | A triangular area at the anterior inferior part of the tympanic membrane, running from the umbo to the periphery, where there is seen a bright reflection of light. Synonym: cone of light, light reflex, Politzer's luminous cone, red reflex, Wilde's triangle. Malacarne's pyramid, a lobule on the undersurface of the cerebellum, the posterior portion of the vermis. (05 Mar 2000) |
| muscular 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) |
| 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) |
| 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) |