Question

Which of the following is true about vertebral development -

a) The notochord forms the annulus fibrosus

b) The sclerotome forms the nucleus pulposus
c) The sclerotome surrounds the notochord only

d) The sclerotome surrounds the notochord and the neural tube

Answer 1

Correct Answer - D 

The sclerotome surrounds the notochord and the neural tube [Ref Langman's embryology 10th/e p. 140] Development of vertebral column The human nervous system develops from neuroectoderm.

 During development, behind the neuroectoderm lies the mesoderm (paraxial mesoderm) that encloses the notochord (a derivative of endoderm). 

This paraxial mesoderm give rise to somites. Somites further differentrated into : Dermatomyotome :- Give rise to skeletal muscles and dermis. 

Sclerotomes :- Give rise to vertebral column. Sclerotornes which surround notochord starts projecting posteriorly (dorsally) to surround neural tube and forms. 

Ventral sclerotomes :- Give rise to vertebral body and annulus fibrosus,

 Lateral sclerotomes :- Give rise to vertebral arch (pedicle and lamina). Dorsal sclerotomes :- Give rise to spinous process. The notochord forms the nucleus pulposus.