8. SGT 06 -The Vertebral Column PDF

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SGT 06 -The Vertebral Column...

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SGT 06: The Vertebral Column        

Identify and describe the major features and structures of the ‘typical’ cervical, thoracic and lumbar vertebrae, and also the sacrum and coccyx. Discriminate between typical vertebrae from different segments of the spinal column and also the atlas, axis and seventh cervical vertebra. Identify the surface anatomy of the vertebral column, its major features and curvatures and demonstrate the normal movements available Appreciate the functional anatomy of the spine and its articulation with the skull and the pelvis. Describe the articulations of the vertebral joints, their ligamentous support and the intrinsic and extrinsic muscles associated with the movements available. Describe the protection of the spinal cord and nerve roots afforded by the bony, ligamentous and cartilaginous components of the back. Describe the functional anatomy of the major muscle groups that mediate movements of the back. Interpret radiographs of the spinal column, identify major anomalies and discuss their clinical relevance.

The Vertebral Column  The vertebral column is divided into five different regions:

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o Cervical (7 vertebrae) o Thoracic (12 vertebrae) o Lumbar (5 vertebrae) o Sacral (5 fused vertebrae) o Coccxy (4 fused verebrae) o Within each reagion the vertebral structure is different. The vertebral column has four main functions: o Protection: encloses and protects the spinal cord o Support: carries the weight of the body above the pelvis. o Hematopoiesis o Movement: Provide points of muscle attachment for movement.

The Structure of a Typical Vertebrae

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All vertebrae consist of an anterior vertebral body, and a posterior vertebral arch. Together the vertebral body and vertebral arch form the vertebral foramen. The foramina of all vertebrae line up to form the vertebral canal (encloses spinal cord). o Vertebral body:  It is the weight-bearing component.  Therefore, vertebrae in the lower portion of the column have larger bodies (to better support the increased weight).  Vertebral bodies articulate with each other via the intervertebral discs. o Vertebral Arch:  Contains several bony prominins which act as attachment points for muscle and ligaments:  Spinous Process  Lamina  Articular Processes: The superior articular process of one vertebrae articulates with the inferior articular process of the vertebrae above it  Pedicles  Transverse Process: In the thoracic vertebrae, the transverse processes articulate with the ribs.

LO: Identify and describe the major features and structures of the ‘typical’ cervical, thoracic and lumbar vertebrae, and also the sacrum and coccyx. LO: Discriminate between typical vertebrae from different segments of the spinal column and also the atlas, axis and seventh cervical vertebra. Distinguishing Features of the Different Vertebrae Region of Vertebral Column Cervical Vertebrae

Distinguishing Features

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Thoracic Vertebrae

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Lumbar Vertebrae

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Sacrum

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Triangular vertebral foramen Bifid spinous process: the spinous process bifurcates (exception C1) Transverse foramina: opening in transverse process for vertebral arteries to travel to brain. Circular vertebral Foramen Spinous process: orientated obliquely and extend inferiorly below vertebral body. Heart shaped vertebral body 2 Demi facets: located superiorly and inferiorly on either side of vertebral body. (Articulate with head of its own rib and the head of the rib below) 1 Costal Facet: located on transverse process. (Articulates with the tubercle of its own rib) Triangular shaped vertebral foramen Kidney shaped vertebral body

Lateral surface has facets for articulation with pelvis. This is how the vertebral column articulates with the pelvis

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Coccyx

 No vertebral arches  No Vertebral Canal Inervertebral Formen  The inferior vertebral notch of one vertebra and the superior vertebral notch of the subjacent vertebra form the intervertebral foramen  spinal nerves enter/exit here

Atypical Cervical Vertebrae Atlas (C1)  Atlas: is the first cervical vertebrae  It articulates with the occipital condyles of the skull and the axis (C2).  Distinguishing Features: o No vertebral body o No spinous process  Articulating Surfaces: o Lateral masses: Contain two sets of facets  Superior articular facet: for articulation with occipital condyles of the skull  Forms the Atlanto-occipital joint  allows for nodding movements  This is how the vertebral column articulates with the skull  Inferior articular facet: for articulation with the axis (C2)  Facet for Dens: (located on the anterior arch)  For articulation with the dens of the axis (C2).  This is secured by a number of ligaments: o Transverse ligament of the atlas o Apical ligament of dens o Alar ligament of dens o Longitudinal fibres

Axis (C2)  Axis: second cervical vertebrae  Distinguishing Feature: o Odontoid process (dens): Extends superiorly and articulates with the dens facet forming the medial Atlanto-axial joint.  Allows for rotation of the head independently of the torso o Superior articular facet: for articulation with inferior articular facets of atlas forming two lateral Atlanto-axial joints.

Vertebrae Prominens (C7)

 Has the longest spinous process (this can be seen sticking out the back of the neck) Radiography  If you look at the spine from an anterior-posterior view you can see a column of owls: o Ears of owl: superior facet o Wings of owl: transverse process o Eyes of owl: pedicles o Feet of owl: inferior facet o Beak of owl: spinous process

Pedicles

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You can visualise the medial Atlanto-axial joint by taking an x ray when someone is opening their mouth.

LO: Identify the surface anatomy of the vertebral column, its major features and curvatures and demonstrate the normal movements available Surface Anatomy of the Vertebral Column

Movements of the Spine  The spine is a capable of the following movements: o Flexion (bending forwards) o Extension (bending backwards) o Lateral flexion (bending right/left) o Lateral extension (returning to normal from lateral flexion) o Rotation

Curvatures of the Spine  The Spine has 4 curvatures: o Cervical curvature (posterior concavity) o Thoracic curvature (anterior concavity) o Lumbar curvature (posterior concavity) o Sacral curvature (anterior concavity)  These curvatures are maintained by the extensors of the back and abdominal flexors.  NB: o Thoracic and sacral are primary curvatures o Lumbar and cervical are secondary curvatures.  Function: o Absorb shocks to your body, protecting the spine.  Degenerations of spinal curvatures:

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Scoliosis: abnormal lateral curvature of the spine. Kyphosis: excessive outwards curve of the spine (hunchback). Occurs in thoracic region. Lordosis: excessive inwards curve of spine. Occurs in the lumbar region.

LO: Describe the articulations of the vertebral joints, their ligamentous support and the intrinsic and extrinsic muscles associated with the movements available. Joints  The mobile vertebrae articulate with each other in the following way: o Facet (zygapophyseal) Joints (synovial Joints)  Left and right superior articular facets articulate with the vertebra above.  Left and right inferior articular facets articulate with the vertebra below.  These joints limit the amount of movement between vertebrae o Vertebral Body Joints (secondary cartilaginous joints)  The articular surfaces of the vertebral bodies are covered by hyaline cartilage

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Vertebral bodies articulate with each other via the intervertebral discs.

Ligaments  Two ligaments strengthen the vertebral body joints: o The anterior and posterior longitudinal ligaments  These run the full length of the vertebral column.  Anterior longitudinal ligament: prevents hyperextension of the vertebral column.  Posterior longitudinal ligament: prevents hyperflexion of vertebral column  The facet joints are strengthened by several ligaments: o Ligamentum flavum: extends between the lamina of adjacent vertebrae o Interspinous and supraspinous ligament: join the spinous processes of adjacent vertebrae.  The interspinous ligament attaches between processes  the supraspinous ligament attaches to the tips o Intertransverse ligaments: extends between transverse processes.  Ligament nuchae: Attaches from the spinous process to external occipital protuberance o This ligament stabilises the skull (keeps it steady e.g. when running)

LO: Describe the protection of the spinal cord and nerve roots afforded by the bony, ligamentous and cartilaginous components of the back. Protection of the Spinal Cord  The spinal cord is protected by the following structures: o Vertebral bodies o Intervertebral discs (act as shock absorbers) o Ligaments o Surrounding muscles o Meninges o CSF Intervertebral Disc  Intervertebral disc: is a fibrocartilaginous cylinder that lies between the vertebral bodies, joining them together. o Not found between C1 and C2 and the sacral or coccyx regions.  Structure: o Each vertebral disc consists of a thick outer ring of fibrous cartilage called the annulus. o This annulus surrounds a more gelatinous core called the nucleus pulposus.

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o The nucleus pulposus is sandwiched inferiorly and superiorly by cartilage end plates. Function: o Act as shock absorbers for the spine o Prevent friction between two moving vertebrae Aging: o As you get older the nucleus pulposus dries out. o This is a problem as its gel like consistency helps to spread weight evenly across the vertebral end plate. o So, when it dries out you get spikes of pressure across vertebral end plate leading to accumulation of microfractures in end plate  degeneration of the spine. Herniated Disc (slipped disc) o Herniation of an intervertebral disc occurs when there is a rupture in the annulus, allowing the nucleus pulposus to break through.  The rupture usually occurs in a posterior-lateral direction, o When the nucleus pulposus breaks through it can irritate nearby spinal nerves  resulting in a variety of neurological and muscular symptoms.  E.g. Sciaticus, which results lower back pain and pain may radiate down the leg, calf and toes.

NB: CT or MRI scans are usually used to show a herniated disc. Muscles in the Back  Muscles in the back can be classified as extrinsic or intrinsic  Extrinsic muscles: o Involved with movements of the upper limbs and thoracic wall o They are innervated by anterior rami of spinal nerves. o The superficial group of extrinsic muscles is related to movement of the upper limb.  Trapezius, latissimus dorsi, Levator scapulae, rhomboid minor, rhomboid major o The intermediate layer of extrinsic muscles is associated with moving the thoracic wall.  They help in respiration:  Serratus posterior superior: lifts the ribs during inspiration  Serratus posterior inferior: pull rubs down during expiration

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Intrinsic muscles o Are deep in position o They are innervated by the posterior rami of spinal nerves. o Splenius: Upper fibres attach to the back of the skull and lower fibres attach into transverse process of upper cervicale vertebrae.  Action:  rotate head to the same side  extend the head and neck o Suboccipital  Extend and rotate the head o Erector Spinae: Made up of the spinalis, longissimus and iliocostalis  Extension of spine  Lateral flexion of spine...