| 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) |
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| 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) |
| 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) |