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