Vertebral  Column
   The vertebral column consists of 26 bones including 24 vertebrae, the sacrum and the coccyx.
  Spinal Curves
   The adult vertebral column shows four spinal curves, cervical, thoracic, lumbar and sacral curves.
      primary curves (accommodation curves) -  these include the thoracic and sacral curves. They appear in fetal development and accommodates the thoracic and abdominopelvic organs.
     secondary curves (compensation curves) - these include the lumbar and cervical curves. They gradually appear after birth and serve to shift weight over the legs as bipedal locomotion develops (walking and running).
 Vertebral Anatomy
   Vertebral body (centrum)
     The weight bearing part of the vertebrae. The vertebral bodies are attached by ligaments and intervertebral discs.
   Vertebral arch (neural arch)
     The vertebral arch forms the vertebral foramen that surrounds the spinal cord. The vertebral arch consists of:
       pedicles - walls of arch that arise from dorsolateral  margins of the body.
       laminae - roof of arch that extend from the top of the pedicles and fuse along the midline.
     Processes that extend from the arch serve as attachment sites for ligaments and muscles. These include:
       spinous process - projects dorsally from midline of arch.
       transverse processes - project laterally or dorsolaterally from the point where pedicles join laminae.
       articular processes - these processes support the joints between neighboring arches. They are:
         superior articular processes - projects cranially (toward the head).
         inferior articular processes - project caudally (toward the tail bone, coccyx).
   Vertebral articulation
      Synovial joints are present where the superior and inferior articular processes interlock. The points of contact, articular facets, are relatively flat surfaces that in the living bone are lined by articular cartilage.
     The vertebral arches together form the vertebral canal that encases the spinal cord. Gaps between the pedicles of successive arches form intervertebral foramina that permit the passage of spinal nerves.
 Vertebral Regions
   Cervical vertebrae
     These 7 vertebrae are the smallest with with small bodies that bear the weight of the skull and large vertebral foramina to accommodate the larger cervical spinal cord. The first two cervical vertebrae have unique features:
     Atlas (C1)
       The atlas articulates with the occipital condyles at a joint that permits nodding. Distinguishing features are:
         Lack of a body.
         Possession of semicircular anterior and posterior vertebral arches.
         Oval superior articular facets and round inferior articular facets.
     Axis (C2)
       During development, the body of C1 fuses to C2 to produce the dens or odontoid process. The dens forms the "axis" around which C1 can pivot to permit rotation of the head from side to side. 
       The cervical vertebrae, as a group, have their own unique features which include: 
         Spinous processes that have a notch on their tips. This results in the processes being described as bifid.
         Transverse processes fuse to costal processes. The fused processes encircle an opening called the transverse foramina that permits the passage of vertebral arteries and veins. 
     Vertebra prominens (C7)
       The last cervical vertebra has some unique features that include a long slender spinous process that ends in a broad tubercle. An elastic ligamentum nuchae extends from the spinous process to the external occipital crest and helps to maintain the upright position of the head. 
   Thoracic Vertebrae
     These 12 vertebrae have heart-shaped bodies and round vertebral foramina. The spinous process project dorsocaudally (downward). All thoracic vertebrae articulate with the ribs and bear evidence of this articulation. These articulations include:
       Costal facets or demifacets are found on the bodies of the vertebrae. The distinction between facet and demifacet (half a facet) rests upon whether the head of the rib articulates on only one body (facet) or overlaps two (demifacet).
       Transverse costal facets are where the tuberculum of the ribs articulates with the transverse processes of the vertebra. These are only on T1 to T10. 
   Lumbar Vertebrae 
     The 5 lumbar vertebrae bear the most weight and are the largest. The large bodies are oval and the vertebral foramen is triangular. The spinous process is stumpy and projects dorsally.
     The sacrum represent the fusion of 5 vertebrae. Transverse lines mark where the bodies of the vertebrae fused. The bone is curved when viewed from the side with a convex dorsal surface. Features include:
       apex - narrow caudal (towards the tailbone) portion.
       base - broad superior portion where there is an articulation with L5.
       sacral promontory - prominent bulge on anterior side of base.
       superior articular processes - articulates with inferior articular processes of L5.
       sacral canal - continuation of vertebral canal through fused arches of sacral vertebrae.
       median sacral crest - fused spinous processes of the first four sacral vertebrae.
       sacral cornua - processes that result from failure of laminae of S5 to form and fuse.
       sacral hiatus - opening that results from failure of laminae of S5 to form and fuse.
       sacral forminae - openings that correspond to intervertebral formina. There are anterior and posterior foramina.
       ala - wing-like extensions on either side of base.
       lateral sacral crest - ridges on either side of median sacral crest.
       auricular surface - ear-shaped surface of the sacroiliac joint.
       sacral tuberosity - roughened area dorsal to auricular surface where ligaments that stabilize the sacroiliac joint attach.
      The coccyx consists of 3-5 fused vertebrae. The coccyx is that attachment site for a number of ligaments and a muscle that constricts the anal opening.
  Thoracic Cage
   The thoracic cage consists of thoracic vertebrae, ribs or costae, and the sternum. It protects organs in the thoracic cavity and serves as attachment site for muscles.
        There are 12 pairs of ribs which include:
         true ribs - connect to the sternum by separate costal cartilages.
         false ribs - do not attach directly to the sternum. Ribs 8-10 have costal cartilages that fuses to the costal cartilage of superior ribs. Ribs 11 and 12 have no connection to the sternum and are called floating ribs.
       Features of ribs include:
         head (capitulum) - slightly enlarged end that lies on or between the bodies of the vertebrae.
         neck - short, narrow section next to the head.
         tubercle - process that articulates with the transverse processes of vertebrae T1 to T10.
         angle - bend where rib curves toward the sternum.
         costal groove - groove on inferior surface that accommodates the blood vessels and nerves.
       The sternum is the flat bone that forms the anterior midline of the thoracic wall. It has three components:
         manubrium - widest and most superior portion of sternum. The notch along the superior border is the jugular notch.
         body - longest and largest portion articulates with ribs 2 to 7.
         xiphoid process - smallest part of sternum. Attached to inferior border of body.