Spinal Cord – It is a thin, long tubular structure which is made up of nervous tissues with the length of 43cm long in women and 45cm in men.. It extends from medulla oblongata in the brainstem to the lumbar region of the vertebral column and encloses the central canal of the spinal cord that contains cerebrospinal fluid. Central Nervous System (CNS) is made up of brain and spinal cord in the human body. In the human body, the spinal cord starts from the occipital bone which passing via foramen magnum and entering the spinal canal at the beginning of the cervical vertebrae. In human body, the diameter of the spinal cord that ranges from 13mmin the cervical and lumbar regions to 6.4mm in the thoracic area.
Spinal cord impulses to and from the brain and control most of the reflex activities. It provides a means of communication between spinal nerves and the brain. It encloses the central canal of the spinal cord and contains cerebrospinal fluid. Spinal cord is formed into two types of neutral tissue, outer white matter and internal grey matter.
Functions – The brain is the command center of the body and the spinal cord is route for messages sent by brain to the body and from body to brain. The spinal cord performs two main function namely the Stimuli passed from and to brains through spinal cord and other being center of spinal reflex action. The main functions of the spinal cord is that the transmission of new signals from the motor cortex to the body and from the different fibers of the sensory neurons to the sensory cortex. Spinal cord contains spinal interneuron which makes up the neutral circuits called as central pattern generators. This type of circuits is used in controlling motor instructions for rhythmic movements such as walking.
Structure – There are about 31 spinal cord nerve segments in a human body which are as given below –
- 8 cervical segments that forms 8 pairs of cervical nerves in human body.
- 12 thoracic segments that forms 12 pairs of thoracic nerves
- 5 lumbar segments that forms 5 pairs of lumbar nerves
- 5 sacral segments that forms 5 pairs of lumbar nerves
- 1 coccygeal segment
Spinal nerves leave each segment in a pair and each pair connects the spinal cord with a specific region of the body.
The spinal cord is covered by three layers of tissues called meninges. These are contained in a spinal cord. The backbones or Vertebrate protect the spinal cord. These are separated by disks which act as cushion. Spinal cord consists of grey and white matter. Center of cord consists of grey matter which transmits information to muscles from brain or spinal cord through motor nerves cells. The white matter contains nerve fibers which carry sensory information to brain from the rest of the body.
There are two regions where the spinal cord enlarges which are as discussed below –
- Lumbar enlargement – It is similar to the lumbosacral plexus nerves that innervate the lower limb and comprises the spinal cord segments between L2 and S3. It is found about the vertebral levels of T9 to T12.
- Cervical enlargement – It corresponds to the lumbosacral plexus nerves that innervate the lower limb and comprises the spinal cord segments between L2 and S3. It is found about the vertebral levels of T9 to T12.