Embryonic Development of the Vertebral Column

Question 1

4 natural curves

Answer 1

Cervical (secondary)
Thoracic (primary)
Lumbar (secondary)
Sacral (primary)

Question 2

5 sections

Answer 2

Cervical (7)
Thoracic (12)
Lumbar (5)
Sacral (5 fused bones)
Coccyx

Question 3

Embryonic development of the vertebral column

Answer 3

Develops during the 4th week from the sclerotomes of somites

Forms from specialisations of the mesoderm

Question 4

Specialisation of embryonic mesoderm

Answer 4

The notocord triggers the intraembryonic mesoderm to form the 3 bends
Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm

Question 5

Paraxial mesoderm

Answer 5

Segments to form somites
Somites differentiate into 2 parts, sclerotome and dermomyotome
Dermotome differentiates into dermotome and myotome
Sclerotome later forms vertebral column

Question 6

Stages of vertebral column development

Answer 6

Mesenchymal stage
Chondrification stage
Ossification stage

Question 7

Mesenchymal stage

Answer 7

4th week of dev, sclerotome cells start to migrate medially to envelop the neural tube and notocord
Each sclerotome will segment into the cranial part (less condensed) and the caudal part (more condensed)
The line between these segments is the Von Ebner’s Fissure
Re-segmentation
Formation of intervertebral discs
Formation of neural arches

Question 8

Resegmentation

Answer 8

Spinal nerves transverse through the sclerotome at Von Ebner’s Fissure
Caudal part of one sclerotome and cranial part of the other fuse to form the vertebral body
Segmented again by spinal nerves

Question 9

Formation of intervertebral discs

Answer 9

The densely packed cells of the caudal part of the sclerotome migrates upwards to the middel of the segment to form the pericaudal disc which later forms the annulus fibrosis
The nucleus pulposus is a gel-like material in the middle, remnant of notocord

Question 10

Development of neural arches

Answer 10

Sclerotome cells will migrate from the centrum on both sides of the neural tube to form neural arches
Neural arches fuse posteriorly to form neural spine
Sclerotomes extend laterally from both sides of the centrum to form lateral and costal processes
(lateral process remains in adults)

Question 11

Chondrification stage

Answer 11

Formation of cartilage from mesenchyme
2 chondrification centers will form in the centrum and then fuse with each other
2 other centers will form in the neural arches and later also fuse with each other
Then spreads throughout entire vertebra so that it is made up of cartilage by then end of the 6th week

Question 12

Ossification stage

Answer 12

3 primary ossification centers form during 8th week
- 1 in centrum
- 2 in neural arches
5 secondary ossification centers will form after puberty

Question 13

5 secondary ossification centers

Answer 13

Superior rim of vertebral body (annular epiphysis)
Inferior rim of vertebral body (annular epiphysis)
Tip of spinous process
Tip of each transverse process

Question 14

Fate of notochord

Answer 14

Degenerates to form nucleus pulposus of intervertebral disc

Question 15

Fate of costal processes

Answer 15

Cervical region degenerates to form ant and lat boundary of transverse foramina
Thoracic region elongates to form ribs
Lumbar region fuses with transverse process to form its ant part
Upper sacral region forms ant portion of the alar of the sacrum

Question 16

Congenital abnomalities

Answer 16

Abnormal number
Abnormal curve
Abnormal fusion

Question 17

Abnormal number

Answer 17

Sacralization
Lumbarization
Klippel-Feil syndrome

Question 18

Abnormal curve

Answer 18

Scoliosis
Lordosis
Kyphosis

Question 19

Abnormal fusion

Answer 19

Spina bifida

Question 20

Klippel-Feil Syndrome

Answer 20

Fewer number of cervical vertebrae
Shortness of neck, low hairline, restricted neck movements
Lack of segmentation of cervical region
Number of cervical nerve roots are normal but smaller