| axis, crystallographic | <microscopy> One of several imaginary lines assumed in describing the positions of the planes by which a crystal is bounded, the positions of the atoms in the structure of the crystal and the directions associated with vectorial and tensorial physical properties. (05 Aug 1998) |
|---|---|
| axis, optic | <microscopy> The direction, or directions in an anisotropic crystal along which light is not doubly refracted. (05 Aug 1998) |
| axis, optical | <microscopy> Usually refers to the axis on which several principal lens axes may lie. It also refers to the axis of the eye which extends through the centre of the eye lens. The line formed by the coinciding principal axes of a series of optical elements comprising an optical system. It is the line passing through the centres of curvature of the optical surfaces. (05 Aug 1998) |
| axis, principal | <microscopy> A line conceived as passing through the centre of a lens to connect the centres of curvature of the lens surfaces. The focal points of a lens lie on the principal axis. (05 Aug 1998) |
| axis-traction forceps | Obstetrical forceps provided with a second handle so attached that traction can be made in the line in which the head must move in the axis of the pelvis. (05 Mar 2000) |
| axisymmetry | <radiobiology> Geometric property of a system which is symmetric about an axis of rotation. For example: an ideal circular torus is symmetric about the axis running through the centre of the torus (like the axle of a wheel). (09 Oct 1997) |
| condylar axis | A line through the two mandibular condyles around which the mandible may rotate during a part of the opening movement. Synonym: condyle cord. (05 Mar 2000) |
|---|---|
| conjugate axis | Distance from the promontory of the sacrum to the upper posterior edge of the pubic symphysis. Synonym: anteroposterior diameter of the pelvic inlet, conjugata vera, conjugate axis, conjugate diameter of pelvic inlet, diameter mediana, internal conjugate, true conjugate. (05 Mar 2000) |
| craniofacial axis | A straight line passing through the mesethmoid, presphenoid, basisphenoid, and basioccipital bones. (05 Mar 2000) |
| sagittal axis | In dentistry, the line in the frontal plane around which the working side condyle rotates during mandibular movement. (05 Mar 2000) |
| principal optic axis | A line passing through the centre of the lens of a refracting system at right angles to its surface. (05 Mar 2000) |
| Helmholtz' axis ligament | <anatomy> A ligament forming the axis about which the malleus rotates; it consists of two portions extending from the anterior and the posterior border, respectively, of the tympanic notch to the malleus. Synonym: axis ligament of malleus. (05 Mar 2000) |
| hinge axis | An imaginary line around which the mandible may rotate through the horizontal plane. Synonym: hinge axis, mandibular axis. (05 Mar 2000) |
| secondary axis | Any ray passing through the optical centre of a lens. (05 Mar 2000) |
| pupillary axis | A line perpendicular to the surface of the cornea, passing through the centre of the pupil; the "direction of gaze." (05 Mar 2000) |
| neural axis | The central nervous system; the brain and spinal cord. Synonym: encephalomyelonic axis, neural axis. (05 Mar 2000) |
| neutral axis of straight beam | The axis perpendicular to the plane of loading of a beam at stresses within the proportional limit; it lies at the gravity axis of the cross-section of the beam. (05 Mar 2000) |
| normal electrical axis | A mean electrical axis of the heart situated between -30 |
| symmetry axis | <radiobiology> The straight line (usually vertical) through the centre of a configuration, when the configuration is symmetric to all (axisymmetric, like the tokamak) or some (periodic, like the stellarator) rotations about this line. Usually the z-axis. (09 Oct 1997) |
| instantaneous electrical axis | The resultant axis of the electromotive forces developing in the heart at any given moment. (05 Mar 2000) |
| internal axis of eye | <anatomy> That part of the optic axis from the midpoint of the posterior surface of the cornea to the anterior surface of the retina opposite the posterior pole. Synonym: axis bulbi internus. (05 Mar 2000) |