Anatomy of the Back and Spine
In most cases, a person's back pain begins with a problem in one or more sections of the spine. Here we will take a close look at the anatomy of the back and spine, so that we will get a better understanding of how it works, and how we may be affected when things go wrong with it.
The Spinal Cord: The central element of the spine is the spinal cord. The spinal cord is a bundle of spinal nerves that exit the brain, through a hole in the skull called the foramen magnum. The spinal nerves of the spinal cord are really an extension of the brain itself, and it relays signals from the brain and furthest reaches of the body, enabling us to have feeling, conscious motor movements, and the ability of adapt to our environment. The Spinal cord is protected by many different structures in and around the spine, though the meninges of the spinal canal are the structures that immediately surround it. The meninges are supportive layers that surround the spinal cord, that protect it from injury, provide it with oxygen and nutrients, and carry away waste products such as CO2 (Carbon Dioxide). The three meninges layers are known as the Dura Mater, Arachnoid Mater, and Pia Mater.
Together, the spinal cord and the meninges make up a structure known as the spinal canal.
Together, all the nerves and supportive structures make up the central nervous system when they are contained within the brain and spinal cord. Nerves that branch off of the spinal cord and exit through the sides of the spine become part of the peripheral nervous system.
The spinal canal travels from the base of the brain until about the level of L1-L2, which is located near the top of the lumbar spine. The L1-L2 level of the spine, in laymen's terms, is located at the top of the lower back (The spinal nerves do still continue past this point and through the sacral part of the spine). The average total length of the spinal cord is about 17 inches.
There are 33 vertebral bones, though about 9 of these are fused in the average adult male and feel. Together, these vertebral bones are called the spine, or backbone. Though the term backbone may make you think of one solid object making up the foundation of our backs, our spine is a collection of 26 moving bones, with many more supportive structures that offer movement, protection, and nutrition. There are seven vertebrae in the cervical spine, 12 in the thoracic spine, and five in the lumbar spine. Located below the bottom of the last lumbar vertebra is the sacrum and the coccyx below that. The sacrum exists as 5 separate vertebras which become fused together after birth. The coccyx (tailbone) is located just below the sacrum, and exist as 4 separate vertebrae which become fused together after birth.
The spinal canal travels through and within hollow spaces within the bones of the spine (vertebrae). These hollow spaces within the vertebral bones are known as the vertebral foramen. The arch of bone than makes up the wall of the vertebral foramen begins behind the bean-shaped body of the vertebra. The first section of this wall is known as the pedicle. There are two pedicles on each side of the vertebral arch. Continuing from the pedicles are a pair of lamina on each side of the vertebral arch. There is a spinous process that extends from the section where the lamina connect, and the tip of this spinous process is the part of the spine that you can actually see and feel protruding through the skin of a person.
The inner part of the spinal cord consists of grey matter. The outer layer of the spinal cord consists of white matter, which is made up of myelin-sheathed nerve fibers. There are many bundles of nerve fibers within this layer that are each specialized for motor and autonomic nervous system functions, such as the ability to sense pain, heat, and pressure. Other specialized functions of these bundles of nerve fibers are the ability of the body to sense and respond to sensory stimuli and to conduct motor impulses activating glands and muscles. The grey matter within the inner layer is composed mainly of nerve cell bodies. Throughout the length of the spinal cord and into the brain, there is a central canal, containing cerebrospinal fluid. While blood is the lifeline of most of the organs and structures of the body, the cerebrospinal fluid is the lifeline of the spinal cord and brain. The cerebrospinal fluid provides the oxygen and nutrients required for the cells and nerves of the spinal cord to function.
In the event of a spinal cord injury, the nerves of the spinal cord may become injured, resulting in a loss of communication between the body and the central nervous system. This loss of communication may be temporary or permanent. This loss of communication may result in paralysis if the injury is severe.