SPINE ANATOMY - IN BRIEF

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pine is the part which connects the head to the torso and other parts of the body.

Spine is the axial part and is present in the midline. Formed out of 33-34 small bones called as Vertebrae, it acts as a support system to the body.

The spine is divided into the following parts –

1.    Cervical - 7

2.    Thoracic - 12

3.    Lumbar - 5

4.    Sacral – 5 (Fused)

5.    Coccygeal – 4/5 (Fused)

These vertebrae are stacked on top of each other and have an opening in them called as the Vertebral canal. Each vertebra has the following parts –

1.    Body

2.    Laminae

3.    Spinous processes

4.    Transverse processes

Two successive vertebrae are separated by a disc called as intervertebral discs. This whole structure creates a curve called as the spinal curve.

The cervical and Lumbar region has a concave curve, with the concavity opening at the posterior aspect; and the thoracic and sacral regions has a convex curve with the concavity opening anterior aspect.

These curves have been given names and thus are allotted to the regions they belong.

1.    Cervical Lordotic Curve

2.    Thoracic Kyphotic Curve

3.    Lumbar Lordotic Curve

4.    Sacral and Coccygeal Kyphotic Curve.

This curving of the spine helps in maintaining the posture as well as creating a structure where weight distribution is easier. The intervertebral discs acts as a cushion which helps in absorption of any blow or shock. The way in which these vertebrae are stacked on top of each other helps in a slight anterior and posterior movement, they are joint together by the facet joints. Each vertebra has 4 facets; 2 superior facets and 2 inferior facets. The ligaments that hold them together are the ligamentum flavum, anterior longitudinal ligament and the posterior longitudinal ligament.

The thoracic vertebrae are different from that of the cervical and lumbar vertebrae because they have extra facet on the transverse processes called as the costal facet where the head of the rib is attached and this creating the posterior boundary of the thoracic cavity.

The cervical vertebrae are small and get progressively bigger as they proceed down towards the thoracic and lumbar.

The peculiarity of the cervical vertebrae is that the 1^st two vertebrae are involved in the motion of the head rotation. They act as a pivot for the skull forming the Atlanto-occipital joint and the atlantoaxial joint.

The 2^nd cervical vertebra is called as the Axis as it has a prominent anterior structure called as the odontoid process or DENS. This acts as the pivot part for the base of the skull and the 1^st vertebra to freely move around. The 1^st vertebra is called as the ATLAS, because it appears as if the Greek God ATLAS is carrying the World on his shoulders, where the world is the skull itself.

Atlas lifting the earth.

Atlanto-occipital joint.

The C1 and C2 vertebrae also have a sulcus on their transverse processes that acts as a notch for the vertebral artery to anchor and go inside the skull to later to form the basilar artery.

Through the centre of these vertebrae runs the spinal cord that terminates at the level of L3/L4. The conus medullaris is a structure formed by the sacral and coccygeal roots. Cauda equina is the terminating part of the spinal cord and it resembles the horse tail, thus named as CAUDA EQUINA (equina means horse).

Through the intervertebral foramen arises the nerve roots that go peripherally and supply the various parts of the body. The upper limb is supplied by the Brachial plexus which means the nerve connections and routes that supply the arm (brachium means the arm). It arises from the 5^th cervical vertebra and ends at T1. Similar goes for the lower limb which is supplied by the lumbo-sacral plexus.

The spinal cord is supplied by the anterior spinal artery which runs in the anterior fissure of the spinal cord. Whereas the posterior part is supplied by two posterior spinal arteries which then anastomose to complete the circulation.