| frontal sinus aperture | One of a pair of openings in the floor of the frontal sinuses in the nasal part of the frontal bone, through which the frontal sinuses communicate with the ethmoidal infundibulum via the frontonasal duct. Synonym: apertura sinus frontalis. (05 Mar 2000) |
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| frontal sinusitis | Inflammation of the frontal sinus; in most cases the infection is caused by the bacteria streptococcus pneumoniae and haemophilus influenzae. This condition may be acute or chronic. (12 Dec 1998) |
| frontal squama | The tabular or squamous portion of occipital bone. Synonym: squama occipitalis, occipital squama, frontal squama. (05 Mar 2000) |
| frontal suture | The suture between the two halves of the frontal bone, usually obliterated by about the sixth year; if persistent it is called a metropic suture. Synonym: sutura frontalis. (05 Mar 2000) |
| frontal tuber | The most prominent portion of the frontal bone on either side. Synonym: tuber frontale, eminentia frontalis, frontal tuber. (05 Mar 2000) |
| frontal veins | The superficial veins draining the frontal cortex and emptying into the superior sagittal sinus. Synonym: supratrochlear veins. (05 Mar 2000) |
| frontal zone contraction theory | Model proposed to account for the movement of giant amoebae in which cytoplasmic contraction at the front of the leading pseudopod (fountain zone) pulls viscoelastic cytoplasm forward in the centre of the cell and forms a tube of more rigid cytoplasm immediately below the plasma membrane behind the active region. The peripheral contracted cytoplasm relaxes into a weaker gel at the rear and is pulled forward in its turn. Contrasts with the ectoplasmic tube contraction model. (18 Nov 1997) |
| anal triangle | The posterior portion of the perineal region through which the anal canal opens; bounded by a line through both isehial tuberosities, the sacrotuberous ligaments and the coccyx. Synonym: regio analis, anal region. (05 Mar 2000) |
| anterior triangle of neck | The area of the neck bounded by the mandible, the anterior border of the sternocleidomastoid muscle, and the anterior midline of the neck; it is subdivided into carotid, muscular, submandibular, and submental triangles. Synonym: anterior region of neck, regio cervicalis anterior, trigonum cervicale anterius. (05 Mar 2000) |
| Assezat's triangle | A triangle formed by lines connecting the nasion with the alveolar and nasal point; used to indicate prognathism in comparative craniology. (05 Mar 2000) |
| auricular triangle | A triangle formed by the base of the auricle and by lines drawn from the true tip of the auricle to the extremities of the base. (05 Mar 2000) |
| axillary triangle | A triangular area embracing the medial aspect of the arm, the axilla, and the pectoral region which is one of the seats of predilection for the petechial initial rash of smallpox. (05 Mar 2000) |
| Beclard's triangle | Area bounded by the posterior border of the hyoglossus muscle, the posterior belly of the digastric and the greater horn of the hyoid bone. (05 Mar 2000) |
| Bonwill triangle | An equilateral triangle formed by lines from the contact points of the lower central incisors, or the medial line of the residual ridge of the mandible, to the condyle on either side and from one condyle to the other. (05 Mar 2000) |
| Bryant's 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) |