NOTES ON THE STRUCTURE OF THE RACHIS

The vertebral column, also called rachis, is composed of 33-34 vertebrae. On the basis of the different configuration of the vertebrae it can be divided into four sections which, named in the cranio-caudal sense are: cervical, dorsal, lumbar, sacred. The first and third under physiological conditions form lordotic curves (curves of the column to posterior concavity) , while the other two form kyphotic curves (curves of the column with anterior concavity).

In the fetus, the spine appears as a single C-shaped curve. Even before birth, a cervical countercurve begins to appear (cervical lordosis), which will then develop after birth in parallel with the stages of acquisition of the ability to extend the head^[1]Bagnall, K. M., P. F. Harris, and P. R. Jones. “A radiographic study of the human fetal spine. 1. The development of the secondary cervical curvature.” Journal of anatomy 123.Pt 3 1977: … Continue reading ^[2]Been, Ella, Sara Shefi, and Michalle Soudack. “Cervical lordosis: the effect of age and gender.” The Spine Journal 17.6 2017: 880-888.. At the lumbar countercurve (lumbar lordosis) it develops in relation to the achievement of the upright position and walking.

The lordoses (cervical and lumbar), also called secondary curves, they allow to recover the horizontality of the gaze by counterbalancing the inclination given by the kyphotic curves. (dorsal and sacral), also called primary curves due to the fact which preserve the original trend of the first large fetal C, among other things they have the task of welcoming and protecting in their heart concavity, lungs and pelvic organs. The alternation of the primary and secondary curves gives the structure of the spine the ability to cushion the weight and to bear considerable levels of load stress.