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Rotation of body parts may be internal or external, that is, towards or away from the center of the body. [22] Internal rotation (medial rotation or intorsion) is rotation towards the axis of the body, [22] carried out by internal rotators. External rotation (lateral rotation or extorsion) is rotation away from the center of the body, [22 ...
A sphere rotating (spinning) about an axis. Rotation or rotational motion is the circular movement of an object around a central line, known as an axis of rotation.A plane figure can rotate in either a clockwise or counterclockwise sense around a perpendicular axis intersecting anywhere inside or outside the figure at a center of rotation.
Rotation around a fixed axis or axial rotation is a special case of rotational motion around an axis of rotation fixed, stationary, or static in three-dimensional space. This type of motion excludes the possibility of the instantaneous axis of rotation changing its orientation and cannot describe such phenomena as wobbling or precession .
Specifically, the body is free to change position as forward/backward (surge), up/down (heave), left/right (sway) translation in three perpendicular axes, combined with changes in orientation through rotation about three perpendicular axes, often termed yaw (normal axis), pitch (transverse axis), and roll (longitudinal axis).
The atlas and axis are specialized to allow a greater range of motion than normal vertebrae. They are responsible for the nodding and rotation movements of the head. The atlanto-occipital joint allows the head to nod up and down on the vertebral column. The dens acts as a pivot that allows the atlas and attached head to rotate on the axis, side ...
In anatomy, the axis (from Latin axis, "axle") is the second cervical vertebra (C2) of the spine, immediately inferior to the atlas, upon which the head rests. The spinal cord passes through the axis. The defining feature of the axis is its strong bony protrusion known as the dens, which rises from the superior aspect of the bone.
An anatomical plane is a hypothetical plane used to transect the body, in order to describe the location of structures or the direction of movements. In human and non-human anatomy, three principal planes are used: The sagittal plane or lateral plane (longitudinal, anteroposterior) is a plane parallel to the sagittal suture. It divides the body ...
Therefore, the instant center of rotation P of body BAC is the point where the lines through P 1-A and P 2-B cross. Since this instant center of rotation P is the center for all points on the body BAC for any random point, say point C, the speed and direction of movement may be determined: connect P to C.