The last lumbar vertebra (L5) articulates (moves) with the sacrum. The sacrum fits between the two hipbones connecting the spine to the pelvis. Five bones (abbreviated S1 through S5) fused into a triangular shape, form the sacrum. The vertebrae are composed of many elements that are critical to the overall function of the spine, which include the intervertebral discs and facet joints.įunctions of the Vertebral or Spinal Column Include: Protection The natural curves in the spine, kyphotic and lordotic, provide resistance and elasticity in distributing body weight and axial loads sustained during movement. Upper body weight is distributed through the spine to the sacrum and pelvis. The intervertebral foramen (neural passageways) are relatively large but nerve root compression is more common than in the thoracic spine.Īlthough vertebrae range in size cervical the smallest, lumbar the largest, vertebral bodies are the weight bearing structures of the spinal column. The spinous processes are horizontal and more squared in shape. The pedicles are longer and wider than those in the thoracic spine. These vertebrae bear much of the body's weight and related biomechanical stress. The lumbar vertebrae graduate in size from L1 through L5. At T11 and T12, the ribs do not attach and are so are called "floating ribs." The thoracic spine's range of motion is limited due to the many rib/vertebrae connections and the long spinous processes. The rib cage is joined to the thoracic vertebrae. They are characterized by small pedicles, long spinous processes, and relatively large intervertebral foramen (neural passageways), which result in less incidence of nerve compression.ġ-Vertebral Body 2-Spinous Process 3-Transverse FacetĤ-Pedicle 5-Foramen 6-Lamina 7-Superior Facet The thoracic vertebrae increase in size from T1 through T12. The dens provides a type of pivot and collar allowing the head and atlas to rotate around the dens. It is also referred to as the ‘dens’ (Latin for ‘tooth’) or odontoid process. It is a blunt tooth–like process that projects upward. The Axis is the second cervical vertebra or C2. The atlas is a ring of bone made up of two lateral masses joined at the front and back by the anterior arch and the posterior arch. Its appearance is different from the other spinal vertebrae. The Atlas is the first cervical vertebra and therefore abbreviated C1. The Occiput (CO), also known as the Occipital Bone, is a flat bone that forms the back of the head. The cervical spine is further divided into two parts the upper cervical region (C1 and C2), and the lower cervical region (C3 through C7). The vertebrae are stacked on top of each other group into four regions: The spinal column (or vertebral column) extends from the skull to the pelvis and is made up of 33 individual bones termed vertebrae.