Vertebral Column Development

Question 1

What part of the paraxial mesoderm develops into axial skeleton?

What 3 areas are cells from this part found in mainly during the precartilaginous stage of development?

Answer 1

Sclerotome

• around notochord
• surrounding neural tube
• in body wall

Question 2

Describe cell arrangement in a sclerotome.

What happens/forms when this cell arrangement shifts?

Answer 2

loosely packed cells cranially, densely packed cells caudally

• densely packed cells move cranially and form the intervertebral disc
• other densely packed cells fuse w/ loose cells and form centrum, primordium of vertebral body

Question 3

What gene plays an essential role in vertebral development?

Answer 3

Pax-1

Question 4

What happens to the notochord during vertebral column development?

Answer 4

it is surrounded by the developing centrums, becomes the nucleus pulposus and is later surrounded by circularly arranged fibers to form anulus fibrosus

Question 5

What mesenchyme from which areas form the various vertebral features?

Answer 5

vertebral arch - mesenchyme around neural tube

costal process - mesenchyme in body wall

Question 6

What are the 2 stages of vertebral development?

Answer 6

cartilaginous

bony

Question 7

Describe the 1st stage of vertebral column development.

Answer 7

Cartilaginous Stage

• **Chondrification Centers **appear in mesenchymal vertebrae (week 6)
• **Centers fuse **to form cartilaginous centrum (end of embryonic period)
• Vertebral arch centers fuse w/ each other and centrum of body
• Spinous + Transverse Processes develop from extensions of centers in arch
• **Chondrification Spreads **until entire column is formed

Question 8

Describe the 2nd stage of vertebral development.

Answer 8

Bony Stage

• 2 Centrum Ossification Centers (dorsal/ventral) fuse to form one
• 3 centers present: 1 centrum, 2 vertebral arch (end of embryonic period)
• Vertebral Arches Fuse within 3-5 years from birth lumbocranially
• Neurocentral Joints btwn arch + centrum allow arch growth w/ spinal cord enlargement
• Centrum Fuses with Arch at year 3-6
• **Secondary Ossification Centers Appear **after puberty
• Secondary Centers Unite w/ Rest around 25

Question 9

What are the 5 secondary ossification centers that appear in vertebrae after puberty?

Answer 9

• 1 in spinous process tip
• 1 in each transverse process tip (2)
• anular epiphyses on sup./inf. rim of body (2)

Question 10

What vertebrae are exceptions to the normal vertebral ossification?

Answer 10

Atlas, Axis, Prominens, Lumbar, Sacrum and Coccyx