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The first two cervical vertebrae, the axis and atlas, are shaped differently from the remaining five. The atlas and axis are responsible for movement of the skull from side to side (cervical rotation to the right and left); also moving forward and backward (cervical flexion and extension). Excessive extension and flexion can disrupt the vertebrae.
Extension is the opposite of flexion, a straightening movement that increases the angle between body parts. [12] For example, when standing up, the knees are extended. When a joint can move forward and backward, such as the neck and trunk, extension is movement in the posterior direction. [ 10 ]
The movement of nodding the head takes place predominantly through flexion and extension at the atlanto-occipital joint between the atlas and the occipital bone. However, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself.
(b) slight lateral motion, lateroflexion, to one or other side around the anteroposterior axis. Flexion is produced mainly by the action of the longi capitis and recti capitis anteriores ; extension by the recti capitis posteriores major and minor , the obliquus capitis superior , the semispinalis capitis , splenius capitis ...
This type of connection permits a wide range of motion in most directions, while still protecting the underlying nerve cord. The central point of rotation is located at the midline of each centrum, and therefore flexion of the muscle surrounding the vertebral column does not lead to an opening between vertebrae. [27]
Those in the lateral compartment only have weak participation in plantar flexion though. The range of motion for plantar flexion is usually indicated in the literature as 30° to 40°, but sometimes also 50°. The nerves are primarily from the sacral spinal cord roots S1 and S2. Compression of S1 roots may result in weakness in plantarflexion ...
In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed (bent) elbow. Straightening of the arm would require extension at the elbow joint.
A functional spinal unit (FSU), or motion segment, is the smallest physiological motion unit of the spine to exhibit biomechanical [1] characteristics similar to those of the entire spine. [ 2 ] A FSU consists of two adjacent vertebrae , the intervertebral disc and all adjoining ligaments between them and excludes other connecting tissues such ...