Development of Vertebral Column and Ribs

Question 1

Vertebrae form from…

Answer 1

Sclerotome

Question 2

4th week sclerotome migrates around…

Answer 2

The spinal Cord and notochord

Question 3

Future vertebral body

Answer 3

Mesenchymal tissue formed by the fusion of the remaining densely packed cells with the loosely arranged cells of the immediately caudal sclerotome

Question 4

Intervertebral disc

Answer 4

formed by densely packed cells which move cranially, opposite the center of the myotome

Question 5

Nucleus pulposus

Answer 5

It emerges when the notochord degenerates and disappears where it is surrounded by the
developing vertebral bodies.

Question 6

Anulus fibrosus

Answer 6

formed by circularly-arranged fibers (intersegmental mesenchyme) that surround the nucleus pulposus

Question 7

IV Disc

Answer 7

Anulus fibrosus + Nucleus pulposus

Question 8

6th week

Answer 8

Chondrification centers appear in each mesenchymal vertebra
* two chondrification centers fuse to form a cartilaginous central region.
* Also, the centers in the vertebral arches fuse with each other and become primary ossification centers

Question 9

8th week

Answer 9

Vertebral ossification begins
* Vertebral body ossification centers:
* Two primary ossification centers (ventral and dorsal) for the vertebral body which then fuse to form one center.
* Vertebral arch ossification centers:
* Two primary ossification centers one in each half of the vertebral arch.

Question 10

At birth

Answer 10

Bony halves of the vertebral arch usually fuse between ages 3-5
* Fusion starts in the lumbar region and then progresses cranially
* Neurocentral joints
cartilaginous articulation between the vertebral arch and the centrum
* permit the vertebral arches to grow as the spinal cord enlarges
* vertebral arches fuse with the body during ages 3-6

Question 11

Puberty:

Answer 11

• Five-second ossification centers appear:
  one at the tip of the spinous process
• one at the tip of each transverse process
• two annular epiphyses (superior and inferior rim of the vertebral body)
• All secondary centers fuse around age 25

Question 12

Ribs Development

Answer 12

Develop from the mesenchymal costal processes of the thoracic vertebrae.
* They become cartilaginous during the embryonic period and ossify during the fetal period.
The original site of the union of the
costal processes with the vertebrae
is replaced by costovertebral
joints. (surgen de costovertebral synchondrosis)

Question 13

Clinical Correlations

Answer 13

Hemivertebra
Rachischisis

Question 14

Hemivertebra

Answer 14

• Failure of one of the chondrification centers to appear as a consequence there is failure of half of the vertebra to form
  (Failure of formation of vertebra, failure of segmentation or mixed)
• Scoliosis produced by this vertebral defect

Question 15

Rachischisis

Answer 15

Vertebral abnormality produced by the failure of the neural folds to fuse
Etiology: lack of proper induction by notochord or exposure to teratogenic agents