Chapter 5 Skeletal System Axial Skeleton Vertebral Column

Functions • Surrounds/Protects spinal cord • Provides attachment sites for – Ribs – Muscles of neck and back • Axial support of the trunk (skull to pelvis) • Discs absorb shock and provide flexibility

Vertebral Column (Spine) • 26 single vertebral bones – 7 cervical vertebrae are in the neck – 12 thoracic vertebrae are in the chest region – 5 lumbar vertebrae are associated with the lower back • REMEMBER: 7, 12, 5, 1/1 • intervertebral discs separate vertebrae © 2015 Pearson Education, Inc.

Sacrum and Coccyx • 9 vertebrae fuse to form two composite bones • Sacrum formed by the fusion of 5 vertebrae • Coccyx (tailbone) formed by the fusion of 3 to 5 vertebrae (most common to have 4 fuse) © 2015 Pearson Education, Inc.

Figure 5. 16 The vertebral column. Anterior 1 st cervical vertebra (atlas) 2 nd cervical vertebra (axis) Posterior Cervical curvature (concave) 7 vertebrae, C 1 – C 7 1 st thoracic vertebra Transverse process Spinous process Thoracic curvature (convex) 12 vertebrae, T 1 – T 12 Intervertebral disc Intervertebral foramen 1 st lumbar vertebra Lumbar curvature (concave) 5 vertebrae, L 1 – L 5 Sacral curvature (convex) 5 fused vertebrae Coccyx 4 fused vertebrae

Curvatures of the Sine • Primary curvatures (present at birth) – Spinal curvatures of the thoracic and sacral regions – Present from birth – Form a C-shaped curvature as in newborns • Secondary curvatures (form after birth) – Spinal curvatures of the cervical and lumbar regions – Develop after birth – Form an S-shaped curvature as in adults © 2015 Pearson Education, Inc.

Figure 5. 17 The C-shaped spine typical of a newborn. Primary Curvature: C- Shaped Curvature of the Spine

Figure 5. 18 Abnormal spinal curvatures. (a) Scoliosis (b) Kyphosis (c) Lordosis

Anatomy of a Vertebra • Body (centrum) • Vertebral arch – Pedicle – Lamina • • Vertebral foramen Transverse processes Spinous process Superior and inferior articular processes © 2015 Pearson Education, Inc.

Figure 5. 19 A typical vertebra, superior view. Lamina Posterior Transverse process Spinous process Vertebral arch Superior articular process and facet Pedicle Vertebral foramen Body Anterior

Atlas and Axis- the neck region • Atlas (C 1) – No body – Large depressions to accommodate occipital condyles of the occipital bone • Allows head to nod • Axis (C 2) – Dens (large process) provides pivot point for atlas – Allow head rotation when articulating with atlas

Figure 5. 20 a Regional characteristics of vertebrae. (a) ATLAS AND AXIS Transverse process Posterior arch Anterior arch Superior view of atlas (C 1) Transverse process Spinous process Facet on superior articular process Dens Body Superior view of axis (C 2)

Figure 5. 20 b Regional characteristics of vertebrae. (b) TYPICAL CERVICAL VERTEBRAE Spinous process Vertebral foramen Facet on superior articular process Superior view Superior articular process Spinous process Transverse process Body Transverse process Facet on inferior articular process Right lateral view Transverse foramina of cervical vertebrae are ONLY characteristics of cervical vertebrae

Figure 5. 20 c Regional characteristics of vertebrae. (c) THORACIC VERTEBRAE Only vertebrae to articulate w/ribs Spinous process Vertebral Transverse foramen process Facet on superior Facet articular for rib process Body Facet on Superior view superior Body articular process Facet on Costal facet transverse Spinous for rib process Right lateral view

Figure 5. 20 d Regional characteristics of vertebrae. (d) LUMBAR VERTEBRAE Spinous process Vertebral Transverse foramen process Facet on superior articular process Body Superior view Superior articular process Spinous process Signature short spinous processes Body Facet on inferior articular process Right lateral view

Figure 5. 21 Sacrum and coccyx, posterior view. Sacral canal Ala Superior Auricular articular surface process Body Median sacral crest Sacrum Coccyx Sacral hiatus Posterior sacral foramina