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Chapter 5Skeletal System
Axial SkeletonVertebral 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
© 2015 Pearson Education, Inc.
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)
Figure 5.16 The vertebral column.
1st lumbar vertebra
Intervertebral foramen
Intervertebral disc
Spinous process
Transverse process
1st thoracic vertebra
1st cervical vertebra(atlas)
2nd cervical vertebra(axis)
Anterior Posterior
Cervical curvature (concave)7 vertebrae, C1 – C7
Thoracic curvature (convex)12 vertebrae, T1 – T12
Lumbar curvature (concave)5 vertebrae, L1 – L5
Sacral curvature (convex)5 fused vertebrae
Coccyx4 fused vertebrae
© 2015 Pearson Education, Inc.
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
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
© 2015 Pearson Education, Inc.
Anatomy of a Vertebra
• Body (centrum)• Vertebral arch– Pedicle– Lamina
• Vertebral foramen• Transverse processes• Spinous process• Superior and inferior articular processes
Figure 5.19 A typical vertebra, superior view.
LaminaPosterior
Vertebralarch
Transverseprocess
Spinousprocess
Vertebralforamen
Body
Anterior
Pedicle
Superiorarticularprocessandfacet
Atlas and Axis- the neck region
• Atlas (C1)– No body– Large depressions to accommodate occipital
condyles of the occipital bone• Allows head to nod
• Axis (C2)– Dens (large process) provides pivot point for atlas– Allow head rotation when articulating with atlas
Figure 5.20a Regional characteristics of vertebrae.
Transverseprocess
(a) ATLAS AND AXIS
Posteriorarch
Superior view of axis (C2)
Anterior arch
Superior view of atlas (C1)
Transverseprocess
Spinous process
DensBody
Facet onsuperiorarticularprocess
Figure 5.20b Regional characteristics of vertebrae.
(b) TYPICAL CERVICAL VERTEBRAE
Right lateral view
Spinous processFacet onsuperiorarticularprocess
Vertebralforamen
Transverseprocess
Superior view
Body
Facet on inferiorarticular process
Transverseprocess
Superior articularprocessSpinousprocess
Transverse foramina of cervical vertebrae are ONLY characteristics of cervical vertebrae
Figure 5.20c Regional characteristics of vertebrae.
(c) THORACIC VERTEBRAE
Right lateral view
Transverseprocess
Body
Body
Spinous process
Facetfor rib
Vertebralforamen
Facet on transverseprocess
Spinous process
Costal facetfor rib
Superior view
process
Facet onsuperiorarticular
Facet on superiorarticular process
Only vertebrae to articulate w/ribs
Figure 5.20d Regional characteristics of vertebrae.
(d) LUMBAR VERTEBRAE
Right lateral view
Transverseprocess
Vertebralforamen
Facet on superiorarticular processBody
BodySuperior articularprocess
Spinousprocess
Facet on inferiorarticular process
Superior view
Spinous process
Signature short spinous processes
Figure 5.21 Sacrum and coccyx, posterior view.
Ala
Sacrum
CoccyxSacralhiatus
Posteriorsacralforamina
Mediansacralcrest
Body
Auricularsurface
SuperiorarticularprocessSacral
canal