| olfactory pits | The paired depressions formed when the nasal placodes come to lie below the general external contour of the developing face as a result of the rapid growth of the adjacent nasal elevations; the pit's are the primordia of the rostral portions of the nasal chambers. Synonym: olfactory pits. (05 Mar 2000) |
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| olfactory placodes | Paired ectodermal placode's which come to lie in the bottom of the olfactory pits as the pits are deepened by the growth of the surrounding medial and lateral nasal processes. Synonym: nasal placodes. (05 Mar 2000) |
| olfactory pyramid | A small area of gray matter situated between the roots of the olfactory tracts; it is continuous caudally with the anterior perforated substance. (05 Mar 2000) |
| olfactory receptor cells | Very slender nerve cell's, with large nuclei and surmounted by six to eight long, sensitive cilia in the olfactory epithelium at the roof of the nose; they are the receptors for smell. Synonym: olfactory cells, Schultze's cells. (05 Mar 2000) |
| olfactory receptor neurons | Neurons in the olfactory epithelium with proteins (receptors, odourant) that bind, and thus detect, odourants. Olfactory receptor neurons are bipolar. They send to the surface of the epithelium apical dendrites with non-motile cilia from which project odourant receptor molecules. Their unmyelinated axons synapse in the olfactory bulb of the brain. Unlike other neurons, they can be generated from precursor cells in adults. (12 Dec 1998) |
| olfactory roots | Three distinct fibre bands (stria medialis, stria intermedia, stria lateralis) that caudally extend the olfactory tract beyond its attachment to the olfactory trigone. The medial stria curves dorsally into the tenia tecta; the intermediate, often barely visible, extends straight back and terminates in the olfactory tubercle; the lateral olfactory stria, the largest of the three, passes along the lateral side of the olfactory tubercle, curving laterally as far as the limen insulae, then sharply medially to reach the uncus of the parahippocampal gyrus where it terminates in the plexiform layer of the olfactory cortex. See: medial longitudinal stria. Synonym: striae olfactoriae, olfactory roots. (05 Mar 2000) |
| olfactory striae | Three distinct fibre bands (stria medialis, stria intermedia, stria lateralis) that caudally extend the olfactory tract beyond its attachment to the olfactory trigone. The medial stria curves dorsally into the tenia tecta; the intermediate, often barely visible, extends straight back and terminates in the olfactory tubercle; the lateral olfactory stria, the largest of the three, passes along the lateral side of the olfactory tubercle, curving laterally as far as the limen insulae, then sharply medially to reach the uncus of the parahippocampal gyrus where it terminates in the plexiform layer of the olfactory cortex. See: medial longitudinal stria. Synonym: striae olfactoriae, olfactory roots. (05 Mar 2000) |
| olfactory tract | A nervelike, white band composed primarily of nerve fibres originating from the mitral cells and tufted cells of the olfactory bulb but also containing the scattered cells of the anterior olfactory nucleus. The tract is closely applied to the ventral surface of the frontal lobe, and attaches itself to the base of the cerebral hemisphere at the olfactory trigone, beyond which it extends in the form of the olfactory striae which distribute their fibres to the olfactory tubercle and, in largest number, to the olfactory cortex on and around the uncus of the parahippocampal gyrus. See: olfactory nerves. Synonym: tractus olfactorius, olfactory peduncle. (05 Mar 2000) |
| olfactory trigone | A grayish triangular area corresponding to the attachment of the olfactory peduncle ("olfactory nerve" or olfactory tract) to the base of the brain, at the anterior border of the anterior perforated substance. Synonym: trigonum olfactorium. (05 Mar 2000) |
| olfactory tubercle | A small, oval area at the base of the cerebral hemisphere, between the diverging medial and lateral olfactory striae, in the anteromedial part of the anterior perforated substance; it is formed by a small area of allocortex characterised by the presence of the islands of Calleja. Corresponding to a much more prominent structure in nonprimate mammals (especially rodents and insectivores), the olfactory tubercle receives fibres from the olfactory bulb by way of the intermediate olfactory stria; it has efferent connections with the hypothalamus and the mediodorsal nucleus of the thalamus. Synonym: tuberculum olfactorium. (05 Mar 2000) |
| 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) |