Development of the Spine

Question 1

Function of Spine

Answer 1

Flexibility
Shock absorption
support for extremities and cranium
structural support for respiratory function

Question 2

Stages of Fetal Development

Answer 2

Pre-embryonic Period: first 3 weeks after fertilization

Embryonic Period: lasts from week 3 to week 8, development of organs

Fetal period: week 8 until term, maturation and growth of all structures

Question 3

Early Development

Answer 3

Skeletal, muscular, and neural development is related to the notochord

Cell proliferation occurs at 3 weeks–formation of ectoderm, mesoderm, and endoderm

Proliferation of Mesoderm- formation of 29 pairs of somites, formed in 4th and 5th weeks
–Somites = pair of block like segments that give rise to mm and vertebrae on each side of notochord

Differentiation of Somites = 4 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 8-10 coccygeal somites

Proliferation of Somites- development of 3 areas

1. Dorsal: cells become dermatomes = skin
2. Medially: deep migration = skeletal mm
3. Ventral and Medial: cells migrate to neural tube = sclerotome

Sclerotome- proliferate and differentiate giving rise to vertebral structures including rib buds
– Chrondification begins at CT level, extending cranially to caudally, allows for formation of solid cartilage model of vertebra with no line of demarcation btwen body, neural arch or rib rudiments

Question 4

Ossification

Answer 4

Ossification- primary and secondary centers

• begins during late fetal period and continues after birth
  1. Primary: extend to spinous, transverse, and articular processess
  2. Secondary: develop at the upper and lower portions of vertebral body, tip of spinous process, and each transverse process
• • continues through adolesence, includes ribs

Ossification of axis, atlas, and sacrum:
Atlas: 2 primary and 1 secondary
Axis: 5 primary and 2 secondary, begins near the end of gestation with fusion of odontoid centers, completed in second decade of life
Sacrum: fusion begins in adolescence and completed in 3rd decade of life

Question 5

Spinal Growth

Answer 5

Occurs throughout adolescence

Does not proceed in a uniform linear pattern, however it is linear between 3 y/o to puberty

2 periods of rapid spinal growth:

1. Birth-age 3
2. Adolescent growth spurt

Spinal pubertal growth spurt occurs at different chronologic and tanner ages.
Females: Tanner 2, 8-14 y/o, max growth at 12 y/o, growth spurt lasts 2.5-3 years
Males: Tanner 3, 11-16 years, max growth at 14