Four curves
Seen from the side, the vertebral column curves four times. The neck and the small of the back curve forward, the chest and the sacrum curve backward. The curves bring the weight of the head and trunk over the feet and let the column give a little at each step. The discs between the vertebrae add to the give.
The curves of the vertebral column seen from the side, region by regionWikimedia Commons, William Crochot (Medium69), vsion and Jmarchn, Public domain (Spinal column curvature-en.svg)
A newborn's spine has a single C-shaped curve, the shape it had in the womb. The neck curve forms in the first months, when the baby starts to hold its head up, and the lumbar curve when it starts to sit and walk.
A column can also bend too far. Scoliosis is a sideways bend with a twist, most often first seen in children around puberty. Kyphosis is an increased forward bend of the upper back.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapter on the back.
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