Cervical Vertebrae – The Anatomy.

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Cervical Vertebrae

Cervical vertebrae are seven in number. The first, second, and

seventh are modified (or) atypical vertebrae.

 They have large vertebral foramen to accommodate the

cervical swelling of the medulla. All cervical vertebrae have a foramen in

the each side of the transverse process known as Foramen Trasversorium

through which vertebral artery, vein and plexus of nerves are transmitted.

The body of the vertebrae is oval and its superior surface is

concave from side to side.

Pedicles

These are short in size and projects upwards and backwards from

the middle of posterolateral parts of body and then from the

posteromedial wall of the foramen transversorium.

Laminae

These are long and rectangular and almost overlap their neighbours

in extension

Spinous Processes

These are short and bifid.

Articular Facets

These are the oblique cut ends of short bone, the articular process

lying at the junction of pedicle and laminae on each side. The superior

facet faces upwards and backwards, the inferior facet faces downwards

and forwards.

Verterbral Foramen

It is large and triangular in shape.

Transverse Process

Each transverse process is short and perforated by the foramen

transversorium. The costal process projects laterally from the body.

Behind the transverse foramen, the true transverse process lies laterally

from the junction of pedicle and laminae to end in posterior tubercle.

Atypical Cervical Vertebrae

Atlas

It supports the globe of head. It has no body. It consists of two

lateral masses united by an anterior and posterior arch. The body

represented by the dens, a tooth like projection from the superior surface

of body of C2. Lamina is present in posterior arch. It is grooved on its

superior surface behind the lateral mass. The spine is replaced by the

posterior tubercle. The superior and inferior facets lie on the lateral

masses anterior to the first and second cervical nerves respectively.

The Axis

The axis has a peg like projection in the upper part of body known

as dens (or) Odontoid process. It has a circular facet anteriorly,

articulating with atlas. There are two articular facets on either side.

Laminae are thick. The spine is large bifid and powerful. The transverse

processes are small and possess a tubercle on its tip.

Seventh Cervical Vertebrae

The spine is long and non-bifid. The transverse process does not

posses anterior tubercle. The foramen transversorium transmits only

veins.

Joints of Vertebral Column

The vertebrae from the 2nd cervical to lst sacral inclusive are

articulated to one another by series of cartilaginous joints between

vertebral bodies and a series of synovial joints between the vertebral

arches. The vertebral bodies are united by antero-posterior longitudinal

ligaments and by a central vertebral disc of fibro cartilage.

Atlanto-occipital Joint

It is a synovial condyloid variety joint. Articular ends are

superiorly with convex occipital condyles, and inferiorly with superior

articular facets of the atlas. Ligaments, capsules, anterior and posterior

atlanto occipital membranes are the adjacent structures. Vertebral artery

supply to this joint. Nerve supply is by first cervical nerve. Movements

flexion, extension and lateral-flexion.

Atlanto-axial Joint

Comprises of

a) A pair of lateral atlanto axial joints and

b) Median atlanto-axial joints

a) Lateral Atlanto Axial Joint

Synovial Joint : Plane variety

Articular Ends : Inferior facets of atlas and superior facets of axis.

Ligaments : Anterior longitudinal ligament and

Ligamentum flavum.

b) Median atlanto axial joint

Synovial Joint : Pivotvariety

Articular Ends : Between the dens of axis, anterior arch of atlas.

Ligaments : Transverse ligament

Movements : Rotatory movements around a vertical axis.

Ligaments Between the Axis and Occipital Bone:

1. Occipito – Axoid

2. Odontoid / Chech Ligaments

Movement – Limit the extend of rotation of craniam

The Unco Vertebral Joints (Luschka’s Joints)

These are not true synovial joints, which develop as a result of

degenerative changes in the edges of the disc in early adult life.

Luschka’s are important because

a) They are commonest site of osteophyte formation. These

osteophytes may compress the cervical nerves.

b) Vertebral artery lies lateral to the joints. Intruding on the canal

can cause distortion of the artery and leads to vertebro basilar

insufficiency in atherosclerotic vessels.

Blood supply of vertebral column:

Vertebrae and longitudinal muscles attached to them are supplied

by segmental arteries. The ascending cervical, intercostals, and lumbar

arteries give multiple small branches to the vertebral bodies. The extensor

muscles are supplied by occipital, deep cervical, and the transverse

cervical arteries. In thoracic and lumbar regions the muscle receives

posterior branches of the intercostals, lumbar, and lateral sacral arteries.

Venous drainage

The internal venous plexus lies within the vertebral canal but

outside the spinal dura. It received tributaries from

i) The vertebrae through the basilo vertebral veins

ii) The meninges and the spinal cord

The internal vertebral venous plexus drained by the intervertebral

veins which passout through the intervertebral foramina. Here they are

joined by the tributaries from the external vertebral and sacral veins.

About the internal nervous plexus communicate with the occipital and

basilar veins through the foramen magnum.

Nerve supply of vertebral column

The anterior longititudinal ligament has rich innervation from the

vertebral plexus which derives sensory innervation from cervical,

glossopharyngeal and vagus nerves and autonomic supply from inferior

cervical and stellate ganglion. The sinus vertebral nerves and the

sympathetic fibers supply posterior longitudinal ligament and perisoteum.

The apophyseal joints and the interspinous ligaments are supplied by

dorsal rami. There is significant overlap of segmental innervation.

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