The range of motion as well as the direction of motion for the various regions of the spine differs. for example the lumbar spine is capable of flexion and extension but little rotational movement. while the thoracic spine rotates with little flexion or extension. this is due to variation in

a. the thickness of the intervertebral disc
b. the arrangement of muscular attachment to the spinous processes
c. the composition of the intervertebral disks
d. the orientation of the superior and inferior articular facets

The correct answer will be option-D

Explanation:

A Facet joint is a synovial joint present between the inferior articular process of one vertebra to the superior articular process of another vertebra.

The facet joints form articular pillars which provide the structural stability and can have different orientation depending on the plane or angle they form.

1. When the articulating facets lie parallel to the frontal plane and form 45° angle to the transverse plane then it allows all the movements in the cervical spine.

2.  When the articulating facets 20° to the frontal plane and 60° to the transverse plane then it allows the lateral flexion and rotation in the thoracic spine region.

3. When the articulating facets form 45° to the frontal plane and they are at right angles to the transverse plane then it allows only flexion and extension in the lumbar region.

Thus, option-D is the correct answer.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.

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