The spine and spinal cord
Five segments of the vertebral column
The spinal column houses the spinal cord and is often referred to as the vertebral column. This vertebrae are classified in five segments as detailed below.
Seven vertebrae make up the cervical spine with eight pairs of cervical nerves. The individual cervical vertebrae are abbreviated C1, C2, C3, C4, C5, C6 and C7.
The Thoracic spine is located in the chest area and contains 12 vertebrae. The ribs connect to the thoracic spine and protect many vital organs. Individual vertebrae are abbreviated to T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11 and T12.
These five bones are the largest vertebrae in the spinal column. These vertebrae support most of the body's weight and are attached to many of the back muscles. Individual vertebrae ate abbreviated to L1, L2, L3, L4, and L5.
The sacrum is a triangular bone located just below the lumbar vertebrae. It consists of four or five sacral vertebrae in a child, which become fused into a single bone in adulthood.
The bottom of the spinal column is called the coccyx. This consists of 3-5 bones that are again fused in an adult.
The spinal cord
Spinal cord overview
The spinal cord is part of the nervous system and runs the length of the back, extending from the base of the brain at the medulla to about the waist at the conus medularis. The spinal cord is housed within the spinal column. Within the column, the cord is surrounded by cerebral spinal fluid. This fluid acts as a buffer to protect the spinal cord from damage sustained by striking the inside of the vertebral column.
Spinal cord illustration
The diagram below illustrates the main anatomical features of the spinal cord. The function of the main areas highlighted are listed below.
Spinal Nerve – Carries nerve impulses
Dorsal Root Ganglion – Receives impulses from other areas such as the skin for transmission to the brain.
Central Canal – Fluid filled space running the length of the spinal cord
Grey Matter – Contains nerve cell bodies.
White Matter – contains the axons of the spinal cord.
Spinal cord function
The spinal cord carries out two main functions, and is effectively a highway for communication of signals.
Firstly, it connects a large part of the nervous system to the brain. Nerve impulses are transmitted to the spinal cord through sensory neurons. These impulses are then transmitted by the spinal cord to the brain. This pathway is known as the ascending tract of nerves. In the reverse process, impulses are generated in the brain, which are transmitted down the cord and leave by the motor neurons. This pathway is known as the descending tract of nerves.
Secondly, the spinal cord acts as a co-ordinating centre in order to produce simple reflexes such as the withdrawal reflex.
The area within the spinal column beyond the end of the spinal cord is called the cauda equina. The nerves that branch out from the spinal cord to the other parts of the body are called lower motor neurons (LMNs) and dorsal root sensory neurons.