axis

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axis

 [ak´sis] (pl. ax´es)
1. a line through a center of a body, or about which a structure revolves.
the second cervical vertebra. adj., adj ax´ial.
2. the position of the cylindrical part of a lens, used for correcting astigmatism; the range of values is from 0° to 180°.
celiac axis celiac trunk.
dorsoventral axis one passing from the posterior to the anterior surface of the body.
electrical axis of heart the preponderant direction of current flow through the heart, a consequence of the electromotive forces within the heart. It may be computed on either an instantaneous basis or a mean basis.
frontal axis an imaginary line running from right to left through the center of the eyeball.
axis of heart a line passing through the center of the base of the heart to the apex.
instantaneous electrical axis the electrical axis of the heart determined at a given point in time.
lead axis the imaginary direct line between the two electrodes of the bipolar leads or between the positive electrode and the reference point of the unipolar leads.
mean electrical axis the average direction of the activation or repolarization process during the cardiac cycle; it may be determined for any deflection (P, QRS, ST-T) and in the frontal, transverse, or sagittal plane.
optic axis
1. a line connecting the center of the anterior curvature of the cornea (anterior pole) with that of the posterior curvature of the sclera (posterior pole).
2. the hypothetical straight line passing through the centers of curvature of the front and back surfaces of a simple lens.
phlebostatic axis a point located by drawing an imaginary line from the fourth intercostal space at the sternum and finding its intersection with an imaginary line drawn down the center of the chest below the axillae.
Phlebostatic axis.
sagittal axis an imaginary line extending through the anterior and posterior poles of the eye.
visual axis an imaginary line passing from the midpoint of the visual field to the fovea centralis.
Axes of the eye. From Dorland's , 2000.

ax·is (ax),

, pl.

ax·es

(ak'sis, ak'sēz), Do not confuse this word with access.
1. A straight line joining two opposing poles of a spheric body, about which the body may revolve.
2. The central line of the body or any of its parts.
3. The second cervical vertebra.
5. The central nervous system.
6. An artery that divides, immediately on its origin, into a number of branches, for example, celiac axis.
[L. axle, axis]

axis

(ăk′sĭs)
n. pl. axes (ăk′sēz′)
1. A straight line about which a body or geometric object rotates or may be conceived to rotate.
2. A center line to which parts of a structure or body may be referred.
3. Anatomy
a. The second cervical vertebra on which the head turns.
b. Any of various central structures, such as the spinal column, or standard abstract lines used as a positional referent.

axis

Anatomy 
The second bone of the vertebrae (C2), which contains a distinct bony protuberance, the odontoid process (dens), on which the first cervical vertebra (C1, the atlas), which carries the head, rotates.

Significance, execution
During judicial hangings, the odontoid process typically breaks off and is forced into the medulla oblongata, which contains the cardiac, respiratory and vasomotor centres that control involuntary functions (e.g., breathing, heart rate and blood pressure), usually resulting in instant death.

Medpspeak
(1) A central or straight line between two structures.
(2) A functional centre between two or more physiologically related activities—e.g., brain-gut axis, hypothalamic-pituitary-adrenal axis.

axis

Medtalk A central or straight line between two structures. See Brain-gut axis, Hypothalamic-pituitary-adrenal axis.

ax·is

, pl. axes (ak'sis, ak'sēz)
1. A straight line joining two opposing poles of a spheric body, about which the body may revolve.
2. The central line of the body or any of its parts.
3. The vertebral column.
4. The central nervous system.
5. The second cervical vertebra.
Synonym(s): epistropheus, vertebra C2, vertebra dentata.
6. An artery that divides, immediately on its origin, into a number of branches, e.g., celiac axis.
See: trunk

axis

1. The second of the vertebrae of the spine, upon which the skull and first vertebra (ATLAS) can rotate. The axis bone has a short, stout vertical peg called the odontoid process around which the atlas can rotate.
2. An imaginary central line of a part or of the body.
3. The meridian in a CYLINDRICAL LENS that possesses no optical power. The curve of maximal power is at right angles to the axis.

Axis

A line that passes through the center of the body or body part.
Mentioned in: Fractures

axis 

A real or imaginary straight line about which a body or system can rotate, or about which a body or system is symmetrical.
achromatic axis A line in the eye along which light passes through all the optical elements and emerges without chromatic dispersion. Although it may lie close to the optical axis it does not necessarily coincide with it. See chromostereopsis; dispersion; chromatic parallax.
anteroposterior axis A line passing through the anterior and posterior poles and the centre of rotation of the eye. It is perpendicular to the transverse (or x-axis) and the vertical (or z-axis). Torsional movements occur around this axis. Syn. sagittal axis; y-axis. See centre of rotation of the eye; poles of the eyeball; torsion.
cylinder axis 1. A line of zero curvature on a cylindrical surface. 2. That principal meridian of a planocylinder in which the power is zero. See astigmatic lens.
axis's of Fick Three mutually perpendicular axes which intersect at the centre of rotation of the eye. They are the x-, y-, and z-axes. Syn. primary axes of Fick. See vertical transverse anteroposterior axis; sagittal plane; xy listing's; yz plane.
fixation axis The line joining the object of regard to the centre of rotation of the eye. Syn. line of fixation.
geometrical axis The line passing through the anterior and posterior poles of the eye. If the refractive surfaces are symmetrical about that axis, it will then coincide with the optical axis.
horizontal axis See transverse axis.
axis notation See standard axis notation.
axis notation, standard The accepted axis notation for cylinders, the same for each eye, whereby the specified axis direction denotes the angle of the cylinder axis with the horizontal measured anticlockwise from 0º to 180º, the front surface of the lens being viewed (British Standard). (Fig. A23) Syn. TABO notation (although the TABO notation specifies the axis direction from 0º to 360º); OCA notation.
optical axis 1. The line joining the optical centres of the refractive surfaces of the eye (a theoretical concept in the eye). A close approximation of this axis is represented by aligning the Purkinje images of a test object (Fig. P14, page 284). 2. The line normal to the surfaces of a lens along which light passes undeviated. See Purkinje-Sanson images.
orbital axis The line from the middle of the orbital opening to the centre of the optic canal. The orbital axes of a normal adult make an angle of approximately 45º with each other. See orbit.
principal axis A line passing through the centre of curvature of a surface and through its vertex.
pupillary axis The line passing through the centre of the entrance pupil of the eye and the pole of the cornea. Syn. pupillary line. See poles of the eyeball.
sagittal axis See anteroposterior axis.
transverse axis A horizontal line passing through the centre of rotation of the eye and lying in Listing's plane. Syn. x-axis. See anteroposterior axis; Listing's plane.
vertical axis A vertical line passing through the centre of rotation of the eye. Syn. z-axis.
visual axis The line joining the object of regard to the foveola and passing through the nodal points which are often considered as coincident, as they are very close to each other. Strictly, this axis is not a single straight line as it consists of two parts: one line connecting the object of regard to the first nodal point and the other line parallel and connecting the second nodal point to the foveola. Syn. visual line. See line of sight.
x-axis See transverse axis.
y-axis See anteroposterior axis.
z-axis See vertical axis.
Fig. A23 Illustration of the standard cylinder axis notationenlarge picture
Fig. A23 Illustration of the standard cylinder axis notation

ax·is

, pl. axes (ak'sis, ak'sēz)
1. [TA] Straight line joining two opposing poles of a spheric body, about which the body may revolve.
2. Central line of the body or any of its parts.
3. [TA] Second cervical vertebra.
4. Vertebral column.
5. Central nervous system.
6. Artery that divides, immediately on its origin, into a number of branches, e.g., celiac axis.