The spinal cord is a part of the central nervous system. It is a long pipe-like structure arising from the medulla oblongata, part of the brain consisting of a collection of nerve fibers, running through the vertebral column of the backbone. In adults, It is usually 40cm long and 2cm wide. It forms a vital link between the brain and the body.
Spinal Cord Anatomy
The spinal cord is divided into five different parts.
- Sacral cord
- Lumbar cord
- Thoracic cord
- Cervical cord
Several spinal nerves emerge out of each segment of the spinal cord. There are 8 pairs of cervical, 5 lumbar, 12 thoracics, 5 sacral, and 1 coccygeal pair of spinal nerves. It performs the primary processing of information as it carries sensory signals from all parts of the body to the Central Nervous System through afferent fibers. And nerve tissue consists of the grey and white matter spread across uniformly. It is a sensitive site, which is severely affected in case of a traumatic injury.
Function Of Spinal Cord
The spinal cord plays a vital role in various aspects of the body’s functioning. Examples of these key functions include:
- Carrying signals from the brain: It can receive signals from the brain that control movement and autonomic functions.
- Carrying information to the brain: The spinal cord nerves also transmit messages to the brain from the body, such as sensations of touch, pressure, and pain.
- Reflex responses: It may also act independently of the brain in conducting motor reflexes. One example is the patellar reflex, which causes a person’s knee to involuntarily jerk when tapped in a certain spot.
Spinal Cord Nerves
The spinal nerves consist of a group of 31 nerves. These nerves are attached to the spinal cord by two roots- dorsal sensory root and ventral motor root.
The sensory root fibers carry sensory impulses to the spinal cord. The motor roots, on the contrary, carry impulses from the spinal cord.
The spinal nerves carry messages to and from the skin of specific regions of the body called dermatomes.
The spinal cord nerves can be grouped as:
- Cervical Nerves: Cervical means of the neck. There are 8 cervical nerves that emerge from the cervical spine (C1-C8).
- Thoracic Nerves: Thoracic means of the chest. There are 12 thoracic nerves that emerge from the thoracic spine (T1-T12).
- Lumbar Nerves: Lumbar means from the lower back region. There are 5 lumbar nerves that emerge from the lumbar spine (L1-L5).
- Sacral Nerves: Sacral means of the sacrum. The sacrum is a bony plate at the base of the vertebral column.
There are 5 sacral nerves that emerge from the sacral bone (S1-S5).
- Coccygeal Nerves: Coccygeal means the tailbone. There is 1 nerve that emerges from the coccygeal bone.
Structure Of Spinal Cord
Cross-section of spinal cord displays grey matter shaped like a butterfly surrounded by a white matter.
Spinal nerves act as mediators, communicating information to and from the rest of the body and the spinal cord. We have 31 pairs of spinal nerves.
Three layers of meninges surround the spinal cord and spinal nerve roots.
- Dura mater
- Arachnoid mater
- Pia mater
Dura mater consists of two layers- periosteal and meningeal. Epidural space is present between the two layers. Subarachnoid space lies between the arachnoid mater and pia mater. It is filled with cerebrospinal fluid.