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ANATOMY AND PHYSIOLOGY OF THE BACKBONE: CURVATURE
Let us now look at the vertebral column as a whole. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae and 5 sacral vertebrae, which fuse completely between 25 to 30 years of age. The total length of the vertebral column of an adult averages 28 inches.The vertebrae do not form a straight and rigid structure. If you look at the spine from the side (see Figure on page 61) you will see that it has several curves, namely (1) the cervical curve, (2) the thoracic curve, (3) the lumbar curve and (4) the sacral curve.The thoracic and sacral curves are called primary curves as they appear by the end of foetal development and are present in the newborn. They are also called ‘accommodation curves’ as they accommodate the thoracic organs (lungs, heart and other related structures) and abdominal and pelvic organs (large intestines, small intestines, uterus, kidney, bladder, rectum etc). These organs are voluminous and they need space, so the spine in the thoracic and sacral regions curves out (convex) to accommodate these organs. In the case of the sacrum, the weight of the abdominal organs tends to push them downwards into the pelvic region where they need ample space to be accommodated.*65\330\8*
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