| 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 triangle | A triangle bounded above by the maximum frontal diameter and laterally by lines joining the extremities of this diameter with the glabella. (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) |
| alveolobuccal sulcus | The upper and lower half of the buccal vestibule on each side. Synonym: alveolobuccal sulcus, gingivobuccal groove, gingivobuccal sulcus. (05 Mar 2000) |
| alveololabial sulcus | The upper and lower half of the labial vestibule, in the embryo, the groove formed by the deepening of the labial sulcus; its inner wall becomes incorporated with the alveolar process of the mandible or the maxilla, and its outer wall with the lips and cheeks. Synonym: alveololabial sulcus, gingivolabial groove, gingivolabial sulcus. (05 Mar 2000) |
| alveololingual sulcus | That part of the oral cavity proper, on each side of the frenulum linguae, between the tongue and the mandibular alveolar process or ridge, in the embryo, the groove on each side between the lingual primordium and the alveolar elevations of the mandible. Synonym: alveololingual sulcus, gingivolingual groove, gingivolingual sulcus. (05 Mar 2000) |
| ampullary sulcus | The groove on the external surface of the ampulla of each saemicircular duct where the nerve enters the crista ampullaris. Synonym: sulcus ampullaris. (05 Mar 2000) |
| anterior intermediate sulcus | A furrow occasionally seen in the adult between the anterior median fissure and the anterior lateral sulcus of the spinal cord but usually present only in the foetus. It indicates the lateral border of the anterior corticospinal fasciculus. Synonym: anterior intermediate groove, sulcus intermedius anterior. (05 Mar 2000) |
| anterior parolfactory sulcus | A fissure marking the anterior border of the parolfactory area. Synonym: sulcus parolfactorius anterior. (05 Mar 2000) |
| anterolateral sulcus | An indistinct furrow on the ventral surface of the spinal cord and medulla oblongata, on either side marking the line of exit of the anterior nerve roots. Synonym: sulcus lateralis anterior, anterolateral groove. (05 Mar 2000) |