| 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) |
| triangle | 1. <geometry> A figure bounded by three lines, and containing three angles. A triangle is either plane, spherical, or curvilinear, according as its sides are straight lines, or arcs of great circles of a sphere, or any curved lines whatever. A plane triangle is designated as scalene, isosceles, or equilateral, according as it has no two sides equal, two sides equal, or all sides equal; and also as right-angled, or oblique-angled, according as it has one right angle, or none; and oblique-angled triangle is either acute-angled, or obtuse-angled, according as all the angles are acute, or one of them obtuse. The terms scalene, isosceles, equilateral, right-angled, acute-angled, and obtuse-angled, are applied to spherical triangles in the same sense as to plane triangles. 2. An instrument of percussion, usually made of a rod of steel, bent into the form of a triangle, open at one angle, and sounded by being struck with a small metallic rod. 3. A draughtsman's square in the form of a right-angled triangle. 4. A kind of frame formed of three poles stuck in the ground and united at the top, to which soldiers were bound when undergoing corporal punishment, now disused. 5. <astronomy> A small constellation situated between Aries and Andromeda. A small constellation near the South Pole, containing three bright stars. <zoology> Triangle spider, a small American spider (Hyptiotes Americanus) of the family Ciniflonidae, living among the dead branches of evergreen trees. It constructs a triangular web, or net, usually composed of four radii crossed by a double elastic fibre. The spider holds the thread at the apex of the web and stretches it tight, but lets go and springs the net when an insect comes in contact with it. Origin: L. Triangulum, fr. Triangulus triangular; tri- (see Tri-) + angulus angle: cf. F. Triangle. See Angle a corner. Source: Websters Dictionary (01 Mar 1998) |
| triangle bandage | <orthopaedics> A cloth (muslin) bandage in the shape of an equilateral triangle. Two triangle bandages can be made by cutting a 36-40 inch cloth square diagonally corner to corner. The triangle bandage is an excellent first aid dressing for scalp wounds and can also be used as a shoulder sling. (19 Jan 1998) |
| triangle of auscultation | Space bounded by the lower border of the trapezius, the latissimus dorsi, and the medial margin of the scapula, where the absence of musculature allows respiratory sounds to be heard clearly with a stethoscope. (05 Mar 2000) |
| triangle of elbow | The fossa in front of the elbow, bounded laterally and medially by the humeral origins of the extensors and flexors of the forearm, respectively, and superiorly by an imaginary line connecting the humeral condyles. Synonym: fossa cubitalis, antecubital space, chelidon, triangle of elbow. (05 Mar 2000) |
| triangle of fillet | 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. Synonym: Reil's triangle, triangle of fillet, trigone of fillet, trigonum lemnisci. (05 Mar 2000) |
| triangle of safety | The area at the lower left sternal border where the pericardium is not covered by lung (pericardial notch); preferred site for aspiration of pericardial fluid. (05 Mar 2000) |
| triangle of vertebral artery | <anatomy, artery> Triangular area in the root of the neck bounded laterally by the scalenus anterior and medially by the longus coli muscles; the two muscles meet at the triangle's apex, formed by the anterior (carotid) tubercle of the transverse process of vertebra C6; the vertebral artery arises from the subclavian artery at the base of the triangle, bisecting the triangle as it ascends to the apex to enter the transverse foramen of vertebra C6. (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) |