| horizontal part of facial canal | First portion of facial canal, between beginning of canal (at the introitus of the facial canal at the end of the internal auditory meatus) and the point at which it turns to descend, beginning the descending part. There are two components (crura) of the horizontal part: the medially-located, anteriorly-directed medial crus and the laterally-placed, posteriorly-directed lateral crus, the two being continuous at a sharp bend, the genu of the facial canal. This lateral part is where the genicular ganglion is located and which communicates with the middle cranial fossa via the hiatus of the facial canal, through which the greater superficial petrosal nerve passes. (05 Mar 2000) |
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| horizontal plane | A plane across the body at right angles to the coronal and sagittal plane's. Synonym: horizontal plane. (05 Mar 2000) |
| horizontal plate of palatine bone | The part of the palatine bone that forms the posterior part (approximately one third) of the bony palate. Synonym: lamina horizontalis ossis palatini. (05 Mar 2000) |
| horizontal resorption | A progressive loss of alveolar and supporting bone surrounding the teeth, beginning at the most coronal level of the bone. Synonym: horizontal resorption. (05 Mar 2000) |
| horizontal survey | <epidemiology> A study of a community, perhaps stratified by age, sex, ethnicity etc., but at one point in time or over a short time interval. Although a snapshot, horizontal surveys of prevalence and intensity within different age classes of a community can nevertheless provide valuable information on the rate at which hosts acquire infection through time, provided that the host and parasite populations have remained approximately stable for a period of time (i.e. Stable endemicity). Same as cross-sectional study , converse of longitudinal study. (05 Dec 1998) |
| horizontal transmission | <epidemiology> Transmission occurring generally within a population, but not including vertical transmission. (05 Dec 1998) |
| horizontal vertigo | Dizziness experienced on lying down. (05 Mar 2000) |
| disease transmission, horizontal | The transmission of infectious disease or pathogens from one individual to another in the same generation. (12 Dec 1998) |
| transverse horizontal axis | An imaginary line around which the mandible may rotate through the horizontal plane. Synonym: hinge axis, mandibular axis. (05 Mar 2000) |
| lateral crus of horizontal part of the facial canal | Laterally-placed, posteriorly-directed second portion of the horizontal part of the facial canal. See: horizontal part of facial canal. Synonym: lateral crus of horizontal part of the facial canal. (05 Mar 2000) |
| Frankfort horizontal plane | A standard craniometric reference plane passing through the right and left porion and the left orbitale; drawn on the profile radiograph or photograph from the superior margin of the acoustic meatus to the orbitale. Synonym: auriculo-infraorbital plane, eye-ear plane, Frankfort horizontal plane, Frankfort plane, infraorbitomeatal plane. (05 Mar 2000) |
| abdominal fissure | Congenital failure of the ventral body wall to close. See: celosomia, gastroschisis. (05 Mar 2000) |
| Ammon's fissure | A pearl-shaped opening in the sclera during early embryogenesis. (05 Mar 2000) |
| anal fissure | A tear or superficial laceration that can occur in the mucosa that lines the anal canal. (27 Sep 1997) |
| anterior median fissure of medulla oblongata | The longitudinal groove in the midline of the anterior aspect of the medulla oblongata; it is the medullary equivalent of the anterior median fissure of the spinal cord and ends at the foramen caecum posterius; its caudal part is obliterated by the decussation of the pyramids. Synonym: fissura mediana anterior medullae oblongatae, anteromedian groove. (05 Mar 2000) |