1- The vertebrae
The spine (or rachis) consists of 26 bones and 33 vertebrae. Of the 33 vertebrae, 9 are fused together to form 2 bones: the sacrum and the coccyx.
The spine measures approximately 70 cm in adults and can be divided into five main sections of vertebrae:
- 7 cervical vertebrae
- 12 dorsal vertebrae
- 5 lumbar vertebrae
- 5 sacral (fused together to form the sacrum)
- 4/5 coccygeal (fused together to form the coccyx)
Every human being has the same number of cervical vertebrae. However, for about 5% of us, the number of other vertebrae may be different.
2- Formation, balance, and curve
Spinal curves control balance. They are formed as a result of the loads imposed by standing and sitting.
Four curves can be observed:
- Cervical
- Thoracic
- Lumbar
- Sacrococcygeal
Since the spine’s ability to withstand stress depends on the ossification of the vertebrae, its final configuration can be observed after puberty.
At birth, the spine has only two of the four curves. Gradually, the cervical curve develops as the baby straightens its head.
- 13 months: The spine is almost aligned.
- 3 years: the lumbar curve is forming correctly.
- 5 years: the dorsal curve is forming and will continue to develop until the age of 20 in boys.
- 8 years: the lumbar curve is more pronounced and obvious.
- At 15 years for girls and 20 years for boys: the curves are permanent.
It should be noted that the development of curvature depends on muscle strength, more specifically the abdominal muscles. Thus, to maintain balance, children adopt a posture, but this posture will not necessarily be the best one for avoiding health problems and back pain.
3- Did you know?
The body’s center of gravity is located 3 cm in front of S2, while the axis of gravity passes through the vertebrae C1, C6 and L3.
The spine can support a load of 1,322.77 pounds.
Image : Häggström, Mikael. “Medical gallery of Mikael Häggström 2014”. WikiJournal of Medicine 1 (2). DOI: 10.15347/wjm/2014.008. ISSN 20018762. Public Domain.
References and additional information:
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