Anatomy of the vertebral column and spinal Cord

The spinal cord is the main pathway for information, connecting the brain to the peripheral nervous system.

The human spinal cord is protected by the bony spinal column (vertebral column). The spinal column is made up of bones called vertebrae.

The spinal cord is located in the vertebral foramen and is made up of 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. A pair of spinal nerves exits from each segment of the spinal cord. The spinal cord is about 45 cm long in men and 43 cm long in women.

The Bony Vertebral Column (Spinal Column)  Ø Supports the head and encloses the spinal cord. Ø There are 33 bones or vertebrae in the spine:   § 7 cervical vertebrae in the neck   § 12 thoracic vertebrae in the upper back corresponding to each      pair of ribs   § 5 lumbar vertebrae in the lower back   § 5 sacral vertebrae are fused together to form 1 bone called      the sacrum   § and 4 coccygeal vertebrae that are also fused to form the      coccyx or tailbone. Ø We refer to the vertebrae by their name and number so that the   cervical vertebrae are C1, C2, C3………..C7 where “C” stands for   “cervical” and the number is the position of the vertebrae counting   down from the head.   § Therefore the thoracic vertebrae become T1 –T12   § The lumbar are L1 – L5   § And the sacrum and coccyx do not have numbers and each is      thought of as one bone.

NOTE:

There are 31 pairs of spinal nerves which branch off from the spinal cord. In the cervical region of the spinal cord, the spinal nerves exit above the vertebrae. A change occurs with the C7 vertebra however, where the C8 spinal nerve exits the vertebra below the C7 vertebra. Therefore, there is an 8th cervical spinal nerve even though there is no 8th cervical vertebra. From the 1st thoracic vertebra downwards, all spinal nerves exit below their equivalent numbered vertebrae.

SPINAL NERVES:                                                                   

1.    cervical nerves (nerves in the neck) supply movement and

     feeling to the arms, neck and upper trunk

2.    thoracic nerves (nerves in the upper back) supply the trunk and

     abdomen

3.    lumbar and sacral nerves (from the lower back) supply the legs

How do the vertebrae relate to the spinal cord ?

The level of the spinal cord segments do not relate exactly to the

  level of the vertebral bodies i.e. damage to the bone at a particular

  level e.g. L5 vertebrae does not necessarily mean damage to the

  spinal cord at the same level.

Ø This is because there are:

  § 7 cervical vertebrae but 8 cervical nerve roots leaving the cord

  § the thoracic spinal cord segments are compressed into the level

     between the T1-T10 vertebrae

  § the lumbar and sacral segments are at the level of the T11 and

     T12 vertebrae

  § the spinal cord ends around the level of the disc between T12

     and L1 vertebrae

  § below this level is an extension of the spinal cord called the

     cauda equina (which means “horses tail” in Latin). The cauda

     equina consists of some of the spinal nerves that are continuing

     down before they pass out between the vertebrae.