9) The Axial Skeleton: The Vertebral Column
Vertebral Arch
Composed of pedicles, laminae, and a spinous process, it represents the junction of all posterior extensions from the vertebral body
Sacrum
Composite bone formed from the fusion of five vertebrae Superiorly articulates with L5, and inferiorly connects with coccyx Concave, forms posterior border of pelvis
Sacral Hiatus
Large opening where sacrum terminates
Sacral Promontory
Anterior border of the body of S1 Important landmark for obstetricians
Vertebrae
Each single bone in the vertebral column (24)
Vertebral Column
Extending from skull to pelvis to form the body's major axial support Surrounds and protects spinal cord while allowing spinal nerves to emerge from the cord
Cervical Vertebrae
First 7 vertebrae Small, wide body Short, bifid spinous process that projects posteriorly Triangular vertebral foramen Transverse process contains foramina Superior articulating processes facets directed superoposteriorly Inferior facets directed inferoanteriorly Flexion and extension allowed, lateral flexion, rotation, spine region with greatest range of movement
Coccyx
Formed by a fusion of three to five irregularly shaped vertebrae Attached to sacrum by ligaments Human tailbone
Lumbar Vertebrae
Last 5 vertebrae Massive kidney shaped body Spinous process is short, blunt, and projects directly posteriorly Triangular vertebral foramen Thin and tapered transverse processes Superior articulating processes facets directed posteromedially Inferior facets directed anterolaterally Flexion and extension allowed, some lateral flexion, no rotation
Thoracic Vertebrae
Middle 12 vertebrae Larger than cervical body, heart shaped, bears costal facets Spinous process is long, sharp, and projects inferiorly Vertebral foramen is circular Transverse processes bear facets for ribs (except T11 and T12) Superior articulating processed facets directed posteriorly Inferior facets directed anteriorly Rotation allowed, lateral flexion possible but limited by ribs, flexion and extension prevented
Vertebral (spinal) Foramen
Opening enclosed by the body and vertebral arch A passageway for the spinal cord
Intervertebral Discs
Pads of fibrocartilage that separate the vertebrae, that cushion the vertebrae and absorb shocks Each has a central gelatinous nucleus pulposus (behaves like a rubber ball) and outer ring of encircling collagen fibers called the anulus fibrosus
Superior and Inferior Articular processes
Paired projections lateral to the vertebral foramen that enable articulation with adjacent vertebrae Superior _______________ typically face posteriorly, whereas the Inferior __________ face anteriorly
Median sacral crest
Part of sacrum Remnant of spinous processes of fused vertebrae
Sacral formina
Part of sacrum located at either side of ridges of sacrum to allow blood vessels and nerves to pass
Sacral canal
Part of sacrum that vertebral canal continues through
Intervertebral Foramina
Right and left pedicles have notches on their inferior and superior surfaces that create openings, the intervertebral foramina, for spinal nerves to leave the spinal cord between adjacent
Body (Centrum)
Rounded central portion of the vertebra, which faces anteriorly in the human vertebral column
Spinous Process
Single medial and posterior projection from the vertebral arch
Transverse Processes
Two lateral projections from the vertebral arch
Alae
Winglike part of sacrum Formed by fusion of transverse processes Articulate laterally with hips