Question

Describe the embryonic development of vertebrae, intervertebral discs and myomeres. Must be more than 100 words.

Answer 1

Sclerotome is migrated to the neural tube. outer to the sclerotome is dermatome and myotome.The nerves need to enter the dermatome and myotome. There are fissure through called as Von Ebners fissure in the scelerotome.These fissure allow nerves to pass to myotome and dermatome . the scleotome of neighbour join to form the actual vertebra.The portion of the adjacent vertebra is called intervertebra disc. At the core of theinterveertebral disc is the nucleus pulposus which is the remaining part of the notochord acts as shock absorber and thete is outerlayer of the intervertebral disc called as annular fibrosus. Annular fibrosus arises from sclereotome.There is mesenchymal vertebrae which is converted into cartilagenous vertebra through chondrification centres which are present at vertebral body and the pedicels from where they extend outwards. The cartilagenous vertebra is then ossified to form the bone.The last portion to be ossified is the spinous process and by that time there are secondary ossificaton centres.The secondary ossification centres is present around the vertebral body called transverse process.The spinous process is connected to spina bifida. The vertebral dfevelopment is endochondral ossification.

Development of myomere takes place from the presomitic mesodem. For the formation of myofibre fusion is important of individual myoblast to form a myofibre.The position of the nuclei is peripheral and is present throughout the myofibre. There is presence of Slit1 derived from sceleotome which helps in the migration and differentiation of the myogenic cell.Vertebral muscle is surrounded by connective tissuecontaing fibroblasts that are embedded  in extracellular matrix.