Anatomy of the Spinal Cord
- Made up of vertebrae (boney parts) & discs (spongy material).
- The vertebrae protect the spinal cord.
- There are:
7 Cervical vertebrae located in the neck
12 Thoracic in the upper/mid back
5 Lumbar in the lower back
5 Sacral in the pelvis
4 coccygeal (tailbone)
- The sacral and coccygeal vertebrae are fused together.
- Each vertebrae consists of a body & arch which form the vertebral foramen in which the spinal cord runs.
- The discs sit between the vertebrae to provide cushioning and shock absorption.
- Ligaments hold the vertebrae together and allow for movement.
- Looks like a rope. It is 18 inches long and approximately the width of the little finger.
- Runs from the base of the brain to the lower part of the back around the L1 vertebrae level.
- At the lower end of the spinal cord the nerves travel a long distance before exiting the spine. This is known as the cauda equina because is looks like a "horse's tail".
- Provides communication between the brain and the body through the spinal nerves.
- 31 pairs of anterior and posterior nerve roots emerge from the spinal cord.
- The anterior nerve roots carry motor nerves.
- The posterior nerve roots carry sensory nerves.
- The anterior and posterior nerve roots join to form two spinal nerves, one on each side of the spine.
- These become the peripheral nerves once they exit the intervertebral foramina.
- There are 8 pairs of peripheral nerves (C1-C7) in the cervical column which exit from the spine on each side above the vertebrae with the same number.
- The C8 nerve pair exits between the C7 and T1 bones.
- There are 12 pairs of thoracic and 5 pairs of lumbar peripheral nerves which exit the spine on each side below the vertebrae with the same number.
- There are 5 sacral and 1 coccygeal pair
Upper Motor Neurons:
- The long nerve fibers inside the spinal cord are known as upper motor neurons (UMNs).
- They run between the brain & the spinal nerves.
Lower Motor Neurons:
- The spinal nerves branch out from the spinal cord into the tissues of the body.
- Spinal nerves are called lower motor neurons (LMNs).
- The LMNs carry the messages to the muscles to coordinate movement.
- The motor nerves carry messages related to movement from the spinal cord (UMNs) to the muscles.
- Each motor nerve connects to a specific muscle, myotome.
- Each level of the spinal cord causes movement in a certain group of muscles.
- The sensory nerves carry messages in different nerve fibers or spinal tracts.
- Nerves in the body collect information and send it up the spinal cord to the brain.
- They carry messages related to pain, touch, heat, cold, vibration, pressure, and knowledge of where a body part is in space.
- Each sensory nerve collects information about feelings from a given body part or area of the skin known as a dermatome. These match a specific spinal cord level.