Vertebral Column Transmits weight of trunk to lower

Vertebral Column • Transmits weight of trunk to lower limbs • Surrounds and protects spinal cord • Flexible curved structure containing 26 irregular bones (vertebrae) • Cervical vertebrae (7)—vertebrae of the neck • Thoracic vertebrae (12)—vertebrae of the thoracic cage • Lumbar vertebrae (5)—vertebra of the lower back • Sacrum—bone inferior to the lumbar vertebrae • Coccyx—terminus of vertebral column Copyright © 2010 Pearson Education, Inc.

Vertebral Column: Curvatures • Increase the resilience and flexibility of the spine • Two posteriorly concave curvatures • Cervical and lumbar • Two posteriorly convex curvatures • Thoracic and sacral • Abnormal spine curvatures • Scoliosis (abnormal lateral curve) • Kyphosis (hunchback) • Lordosis (swayback) Copyright © 2010 Pearson Education, Inc.

C 1 Cervical curvature (concave) 7 vertebrae, C 1–C 7 Spinous process Transverse processes Thoracic curvature (convex) 12 vertebrae, T 1–T 12 Intervertebral discs Intervertebral foramen Lumbar curvature (concave) 5 vertebrae, L 1–L 5 Sacral curvature (convex) 5 fused vertebrae sacrum Anterior view Copyright © 2010 Pearson Education, Inc. Coccyx 4 fused vertebrae Right lateral view Figure 7. 16

Intervertebral Discs • Cushionlike pad composed of two parts 1. Nucleus pulposus • Inner gelatinous nucleus that gives the disc its elasticity and compressibility 2. Anulus fibrosus • Outer collar composed of collagen and fibrocartilage Copyright © 2010 Pearson Education, Inc.

Supraspinous ligament Transverse process Sectioned spinous process Ligamentum flavum Interspinous ligament Intervertebral disc Anterior longitudinal ligament Intervertebral foramen Posterior longitudinal ligament Anulus fibrosus Nucleus pulposus Inferior articular process Sectioned body of vertebra Median section of three vertebrae, illustrating the composition of the discs and the ligaments Copyright © 2010 Pearson Education, Inc. Figure 7. 17 a

Vertebral spinous process (posterior aspect of vertebra) Spinal cord Spinal nerve root Transverse process Herniated portion of disc Anulus fibrosus of disc Nucleus pulposus of disc (c) Superior view of a herniated intervertebral disc Copyright © 2010 Pearson Education, Inc. Figure 7. 17 c

General Structure of Vertebrae • Body or centrum • Anterior weight-bearing region • Vertebral arch • Composed of pedicles and laminae that, along with centrum, enclose vertebral foramen • Vertebral foramina • Together make up vertebral canal for spinal cord • Intervertebral foramina • Lateral openings between adjacent vertebrae for spinal nerves Copyright © 2010 Pearson Education, Inc.

General Structure of Vertebrae • Seven processes per vertebra: • Spinous process—projects posteriorly • Transverse processes (2)—project laterally • Superior articular processes (2)—protrude superiorly inferiorly • Inferior articular processes (2)—protrude inferiorly PLAY Animation: Rotatable Spine (horizontal) PLAY Animation: Rotatable Spine (vertical) Copyright © 2010 Pearson Education, Inc.

Lamina Transverse process Posterior Spinous process Superior articular process and facet Pedicle Anterior Copyright © 2010 Pearson Education, Inc. Vertebral arch Vertebral foramen Body (centrum) Figure 7. 18

Cervical Vertebrae • C 1 to C 7: smallest, lightest vertebrae • C 3 to C 7 share the following features • Oval body • Spinous processes are bifid (except C 7) • Large, triangular vertebral foramen • Transverse foramen in each transverse process Copyright © 2010 Pearson Education, Inc.

Copyright © 2010 Pearson Education, Inc. Table 7. 2

Dens of axis Transverse ligament of atlas C 1 (atlas) C 2 (axis) C 3 Inferior articular process Bifid spinous process Transverse processes C 7 (vertebra prominens) (a) Cervical vertebrae Copyright © 2010 Pearson Education, Inc. Figure 7. 20 a

Cervical Vertebrae • C 1 (atlas) and C 2 (axis) have unique features • Atlas (C 1) • No body or spinous process • Consists of anterior and posterior arches, and two lateral masses • Superior surfaces of lateral masses articulate with the occipital condyles Copyright © 2010 Pearson Education, Inc.

C 1 Posterior Lateral masses Posterior tubercle Posterior arch Anterior arch tubercle (a) Superior view of atlas (C 1) Copyright © 2010 Pearson Education, Inc. Transverse foramen Superior articular facet Posterior arch Transverse process Lateral masses Posterior tubercle Inferior articular facet Transverse Anterior foramen arch Facet for dens Anterior tubercle (b) Inferior view of atlas (C 1) Figure 7. 19 a-b

Cervical Vertebrae • Axis (C 2) • Dens projects superiorly into the anterior arch

Posterior C 2 Inferior articular process Spinous process Lamina Pedicle Transverse process Superior articular facet Dens Body (c) Superior view of axis (C 2) Copyright © 2010 Pearson Education, Inc. Figure 7. 19 c

Thoracic Vertebrae • T 1 to T 12 • All articulate with ribs at facets and demifacets • Long spinous process • Location of articular facets allows rotation of this area of spine Copyright © 2010 Pearson Education, Inc.

Transverse process Superior articular process Transverse costal facet (for tubercle of rib) Intervertebral disc Body Spinous process Inferior costal facet (for head of rib) Inferior articular process (b) Thoracic vertebrae Copyright © 2010 Pearson Education, Inc. Figure 7. 20 b

Lumbar Vertebrae • L 1 to L 5 • Short, thick pedicles and laminae • Flat hatchet-shaped spinous processes • Orientation of articular facets locks lumbar vertebrae together so as to prevent rotation Copyright © 2010 Pearson Education, Inc.

Superior articular process Transverse process Spinous process Body Intervertebral disc Inferior articular process (c)

Sacrum and Coccyx • Sacrum • 5 fused vertebrae (S 1– S 5) • Forms posterior wall of pelvis • Articulates with L 5 superiorly, and with auricular surfaces of the hip bones laterally Copyright © 2010 Pearson Education, Inc. • Coccyx • Tailbone • 3– 5 fused vertebrae • Articulates superiorly with sacrum

Sacral promontory Ala Body of first sacral vertebra Transverse ridges (sites of vertebral fusion) Apex Anterior sacral foramina Coccyx (a) Anterior view Copyright © 2010 Pearson Education, Inc. Figure 7. 21 a

Ala Sacral canal Body Facet of superior articular process Auricular surface Median sacral crest Posterior sacral foramina Coccyx Lateral sacral crest Sacral hiatus (b) Posterior view Copyright © 2010 Pearson Education, Inc. Figure 7. 21 b

Thoracic Cage • Composed of • Thoracic vertebrae • Sternum • Ribs and their costal cartilages • Functions • Protects vital organs of thoracic cavity • Supports shoulder girdle and upper limbs • Provides attachment sites for many muscles, including intercostal muscles used during breathing Copyright © 2010 Pearson Education, Inc.

Sternum (Breastbone) • Three fused bones • Manubrium • Articulates with clavicles and ribs 1 and 2 • Body • Articulates with costal cartilages of ribs 2 through 7 • Xiphoid process • Site of muscle attachment • Not ossified until ~ age 40 Copyright © 2010 Pearson Education, Inc.

Ribs and Their Attachments • 12 pairs • All attach posteriorly to thoracic vertebrae • Pairs 1 through 7 • True (vertebrosternal) ribs • Attach directly to the sternum by individual costal cartilages Copyright © 2010 Pearson Education, Inc.

Ribs and Their Attachments • Pairs 8 through 12 • False ribs • Pairs 8– 10 also called vertebrochondral ribs • Attach indirectly to sternum by joining costal cartilage of rib above • Pairs 11– 12 also called vertebral (floating) ribs • No attachment to sternum Copyright © 2010 Pearson Education, Inc.

Jugular notch Clavicular notch Manubrium Sternal angle Body Xiphisternal joint Xiphoid process True ribs (1– 7) False ribs (8– 12) Sternum Intercostal spaces Costal cartilage Costal margin L 1 Vertebra Floating ribs (11, 12) (a) Skeleton of the thoracic cage, anterior view Copyright © 2010 Pearson Education, Inc. Figure 7. 22 a

Structure of a Typical Rib • Main parts: • Head • Articulates posteriorly with facets (demifacets) on bodies of two adjacent vertebrae • Neck • Tubercle • Articulates posteriorly with transverse costal facet of same-numbered thoracic vertebra • Shaft Copyright © 2010 Pearson Education, Inc.

Transverse costal facet (for tubercle of rib) Angle of rib Superior costal facet (for head of rib) Body of vertebra Head of rib Intervertebral disc Neck of rib Tubercle of rib Shaft Sternum Crosssection of rib Costal groove Costal cartilage (a) Vertebral and sternal articulations of a typical true rib Copyright © 2010 Pearson Education, Inc. Figure 7. 23 a

Articular facet on tubercle of rib Spinous process Shaft Ligaments Neck of rib Head of rib Transverse costal facet (for tubercle of rib) Body of thoracic vertebra Superior costal facet (for head of rib) (b) Superior view of the articulation between a rib and a thoracic vertebra Copyright © 2010 Pearson Education, Inc. Figure 7. 23 b