The Vertebral Column.docx

9 Pages
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Department
Anatomy and Cell Biology
Course Code
Anatomy and Cell Biology 3319
Professor
Kem Rogers

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Description
The Vertebral Column (spinal column or spine) • 26 bones connected into a flexible, curved structure • Main support of body axis • Vertebral column extends from the skull to the pelvis – where it transmits weight of trunk to lower limbs • Surrounds & protects delicate spinal cord & provides attachment points for the ribs & for muscles of the neck & back • In fetuses & infants – vertebral column consists of 33 separate bones or vertebrae • Inferiorly, 9 of these eventually fuse to form 2 composite bones: sacrum & coccyx (tailbone) • Remaining 24 bones persist as individual vertebrae separated by intervertebral discs Regions & Normal Curvatures • About 70 cm (28 inches) long in average adult • 5 major regions o 7 vertebrae of neck – cervical vertebrae o 12 vertebrae of thorax – thoracic vertebrae o 5 vertebrae of lower back – lumbar vertebrae • Vertebrae become progressively larger from cervical to lumbar region as the weight they must support progressively increases o Sacrum – articulates with the hip bones of pelvis o Coccyx – most inferior part of the vertebral column • All people have 7 cervical vertebrae but in 5% of the population variations in numbers of vertebrae • From lateral view – 4 curvatures that give the vertebral column an S shape o Cervical and lumbar curvatures are concave posteriorly o Thoracic and sacral curvatures are convex posteriorly • Curvatures increase resilience of the spine, allowing it to function like a spring rather than a rod • Primary curvatures o Only thoracic and sacral curvatures are well developed at birth o Both are convex posteriorly – infant’s spine arches (C-shaped) like that of a 4 legged animal • Secondary curvatures o Develop during the first 2 years of childhood as intervertebral discs are reshaped o Cervical is present before birth but is not pronounced until a baby starts to lift head at 3 months o Lumbar develops when the baby begins to walk at about 1 year, positions weight of the upper body over lower limbs – providing optimal balance during standing Ligaments of the Spine • Strap-like ligaments of the back & muscles of the trunk – holds the spine • Major supporting ligaments o Anterior & posterior longitudinal ligaments  Run vertically along anterior & posterior surfaces of bodies of vertebrae – from neck to sacrum  Anterior longitudinal ligament • Wide & attaches strongly to both body vertebrae & intervertebral discs • Along with its supporting role – thick anterior ligament prevents hyperextension  Posterior longitudinal ligament • Narrow & relatively weak • Attaches only to intervertebral discs • Helps to prevent hyperflexion o Several other posterior ligaments connect each vertebra to those immediately superior & inferior  Among these is ligamentum flavum – connects lamina of adjacent vertebrae  Stretches as we bend forward then recoils as we straighten to an erect position Intervertebral Discs • Cushion-like pad composed of o Inner sphere o Nucleus pulposus  Gelatinous and acts like a rubber ball  Enables spine to absorb compressive stress o Outer collar of about 12 concentric rings o Anulus fibrosus  Outer rings consist of ligament  Inner rings consist of fibrocartilage  Contain nucleus pulposus – limiting its expansion when the spine is compressed  Binds successive vertebrae together, resting tension on spine, absorbing compression  Collagen fibers in adjacent rings in annulus cross like X, allowing spine to twist  Arrangement creates same antitwisting design providing by bone lamellae in osteons • Act as shock absorbers during walking, jumping, & running • At points of compression, discs flatten & bulge out a bit between vertebrae • Thickest in lumbar (lower back) & cervical (neck) regions of vertebral column • Make up about 25% of the height of the vertebral column • Compression & loss of fluid from nucleus pulposus – discs flatten somewhat by end of the day • Humans are usually 1-2 cm shorter at night than when you awake in the morning Herniated Disc • Caused by severe or sudden physical trauma to the spine (prolapsed discs or slipped discs) • Rupture of the anulus fibrosus followed by protrusion of nucleus pulpous • Aging contributes– nucleus pulposus loses cushioning properties & anulus fibrosus weakens and tears • Anulus is thinnest posteriorly but posterior longitudinal ligament prevents herniation from posterior side • Rupture proceeds posterolaterally – toward spinal nerve roots exiting from spinal cord • Resulting pressure on these nerve roots causes pain or numbness • Most cases pain resolves - conservative treatment: exercise, massage, heat therapy & pain killers • If treatments fail – may be removed surgically and bone grafts are used to fuse adjacent vertebrae • In many cases – back pain results not from herniated disc but instead from small nerves that enter tears in the disc on newly invading veins • IDET treatment – threading fine catheter with heated tip to burning away invading nerves & seal tears General Structure • Body o Anterior portion of vertebra is disc-shaped o Weight-bearing portion of the vertebra • Vertebral arch o Forms posterior portion of the vertebrae o Composed of two pedicles & two laminae o Pedicles  Short, bony walls that project posteriorly from the vertebral body & form the sides of the arch o Laminae  Flat, body plates that complete each arch posteriorly  Extends from transverse processes to spinous process o Protects the spinal cord and spinal nerves located in vertebral foramen • Vertebral foramen o Large hole encircled by the body & vertebral arch o Form the long vertebral canal through which the spinal cord and spinal nerve pass • Spinous process o Median, posterior projection o Arises at the junction of two laminae o It is an attachment site for muscles & ligaments that move & stabilize vertebral column • Transverse process o Projects laterally from each pedicle-lamina junction o Attachment sites for muscle & ligaments • Articular processes o Protrude superiorly & inferiorly from the pedicle-lamina junctions o Form movable joints between successive vertebrae o Inferior articular processes of each vertebra join with superior articular processes of vertebra immediately inferior o Successive vertebrae are joined by both intervertebral discs and by these articular processes o Smooth joint surfaces of these processes are facets • Intervertebral foramina o Notches on superior & inferior borders of the pedicles form lateral openings between adjacent vertebrae o Spinal nerves from spinal cord pass through these foramina Regional Vertebral Characteristics • Different regions of the spine perform slightly different functions – so vertebrae show some variation • Types of movements that can occur between vertebrae o Flexion & extension (anterior bending & posterior straightening) o Lateral flexion (bending upper body to the right or left) o Rotation (rotate on one another in the long axis of the vertebral column) Cervical Vertebrae • C 1C 7 • Smallest, lightest vertebrae • C 1 C -2no intervertebral disc lies between them • Atlas (C 1
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