Lumbar.—There are five lumbar vertebrae.Located in the small of the back, these vertebrae are thelarger and stronger segments of the vertebral column.Sacrum.—The sacrum is the triangular boneimmediately below the lumbar vertebrae. It iscomposed of five separate vertebrae that graduallyfuse together between 18 and 30 years of age. Thesacrum is connected on each side with the hip bone andwith the coccyx to form the posterior wall of the pelvis.THORAX.—This cone-shaped bony cage isabout as wide as it is deep (fig. 1-20). The thorax isformed by 12 ribs on each side and articulatesposteriorly with the thoracic vertebrae. The first set ofribs are attached to the manubrium, a flat irregularbone atop the sternum. The first seven pairs of ribs arecalled true ribs. The remaining five pairs are calledfalse ribs. They are called false ribs because theircartilages do not reach the sternum directly. Theeighth, ninth, and tenth ribs are united by theircartilages and joined to the rib above. The last two ribpairs, also known as floating ribs , have nocartilaginous attachments to the sternum. Thesternum is an elongated flat bone, forming the middleportion of the upper half of the chest wall in front. Thexiphoid process, located at the inferior aspect of thesternum, serves as a landmark in the administration ofcardiopulmonary resuscitation.1-11HM3F0118SPINOUSPROCESSLAMINATRANSVERSEPROCESSSUPERIORARTICULARPROCESSPEDICLEBODYPEDICLEBODYINTERVERTEBRALFORAMENINFERIORARTICULATINGPROCESSSUPERIORARTICULATINGPROCESSTRANSVERSEPROCESSFACET FORTUBERCLEOF RIBSPINOUSPROCESSABFigure 1-18.—Typical vertebra: A. Lateral view of a typicalvertebra; B. Superior view of a typical thoracic vertebra.INTERVERTEBRALFORAMEN3RD TO 7THCERVICALVERTEBRAEHM3F0119AXISATLASFigure 1-19.—Cervical vertebrae.
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