ANATOMY OF SPINE

By

Prof. Dr. Yousri Anwar

INTRODUCTION

The spine is formed of :

_Vertebral column

_Spinal cord

_supporting structures

A. VERTEBRAL COLUMN

FUNCTIONS:

1) Support weight – transmits weight to pelvis and lower limbs

2) Houses and protects spinal cord - spinal nerves leave cord between vertebrae

3) Permits movements

4) Provides for muscle attachments - muscles of back; also muscles of head, neck, upper extremity, thorax

The spinal column consists of individual bones called vertebrae, the building blocks, which provide support for the spine. These vertebrae are connected in the front of the spine by intervertebral discs.

The spinal column consists of:•seven cervical vertebrae (C1–C7) i.e. neck

•twelve thoracic vertebrae (T1–T12) i.e. upper back

•five lumbar vertebrae (L1–L5) i.e. lower back

•five bones (that are joined, or "fused," together in adults) to form the bony

sacrum• three to five bones fused together to form

the coccyx or tailbone

In general a typical vertebra consists of:

• large vertebral body in the front• two strong bony areas called pedicles

connecting the vertebral body and the posterior arch

• an arch of bony structures in the back (posterior arch) = (the spinous process).

BODY

PEDICLE

transverse process

spinous process

2 special cervical vertebrea:

• Atlas:

The atlas is the topmost vertebra

The Atlas has no body, and this is due to the fact that the body of the atlas has fused with that of the next vertebra (the Axis)

it has no spinous process, is ring-like, and consists of an anterior and a posterior arch and two lateral masses

2. Axis:

The second cervical vertebra (C2) of the spine is named the axis The most distinctive characteristic of this bone is the strong dens which rises perpendicularly from the upper surface of the body.

B. Neural Elements:

The neural elements consist of the spinal cord and nerve roots.

The spinal cord runs from the base of the brain down through the cervical and thoracic spine. Below the L1–L2 level the spinal cord ends, as an array of nerve roots continues, looking somewhat like a horse's tail (cauda equina).

It is surrounded by fluid that acts as a buffer to protect the delicate nerve tissues

The cord consists of millions of nerve fibres that transmit information to and from the limbs, trunk and organs of the body.

Nerves called the spinal nerves or nerve roots come off the spinal cord and pass out between the bones to carry the information from the spinal cord to the rest of the body:

_cervical nerves (nerves in the neck) supply movement and feeling to the arms, neck and upper trunk

_thoracic nerves (nerves in the upper back) supply the trunk and abdomen

_lumbar and sacral nerves (from the lower back) supply the legs, the bladder, bowel and sexual organs.

The spinal nerves carry information from different levels (segments) in the spinal cord. Both the nerves and the segments in the spinal cord are numbered in the same way as the bones:

So the cervical nerves and spinal cord segments are called C1- C8, the thoracic are T1-T12, lumbar are L1-L5 and sacral are S1-S5.

C. The supporting structures:

• Intervertebral discs

• Ligaments

• Fascia

• Muscles

The intervertebral discs make up one fourth of the spinal column's length. There are no discs between the Atlas (C1), Axis (C2), and Coccyx. Discs are not vascular and therefore depend on the end plates to diffuse needed nutrients

Discs are composed of two parts: a tough outer portion and a soft inner core:

• The outer portion of the disc (annulus fibrosus) composed of concentric sheets of collagen fibers that seal the gelatinous nucleus and evenly distribute pressure and force imposed on the vertebral column.

• The inner core (nucleus pulposus) contains a loose network of fibers suspended in a mucoprotein gel.

The outer portion and inner core of the spinal disc fit together like two concentric cylinders and are interconnected by cartilaginous end-plates

Ligaments:

Ligaments are rope-like bands of tissue that connect bones together. Most ligaments are lined up to keep joints from bending in the wrong way

The most important ones are:

• Anterior and posterior longitudinal ligaments

• Ligamentum flavum• Supraspinous and

interspinous ligaments

Fascia:

Fascia is similar to ligaments, but fascia is more like a sheet than a rope. The most important of which is the thoracolumbar fascia (TLF) which has the following functions:

As the spinal muscles work, the TLF pulls tightly the low back, keeping the lumbar spine from bending out of the neutral position.

It augments the power generated by spinal muscles.

Muscles:

Because of their location toward the center of the body, and because of their importance in spine stability, these key stabilizers are called "core, paraspinal" muscles

Core muscles help grip and hold the spine. They keep each spinal segment from shifting and sliding as you do your activities

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