The spinal cord begins at the base of the brain and extends into the pelvis. Many of the nerves of the peripheral nervous system, or PNS, branch out from the spinal cord and travel to various parts of the body.
Information from the senses travels through the nerves of the PNS to the spinal cord and then to the brain for processing, and commands from the brain travel down the spinal cord and then to the appropriate part of the PNS, where nerves transport the instructions to the appropriate body part where action is needed.
To facilitate this process, the spinal cord is divided into two kinds of pathways called tracts. Ascending tracts carry sensory input from the body to the brain, and descending tracts carry commands from the brain down to specific tissues and organs.
The spinal cord is also essential for reflex function. Reflexes are the body’s way of coping with stimuli that require an immediate response. For example, jerking away from something hot or sharp is a reflex action. It happens immediately because instructions come from the spine (rather than the brain) to avoid injury.
The spinal cord, like the brain, has two major layers of protection. First are the vertebrae of the spine, and underneath those are three layers of tough membrane called the meninges.
The meninges surround both brain and spinal cord and are filled with a liquid called cerebrospinal fluid. The fluid has several functions, and one of them is shock absorption.
The spinal cord can suffer physical damage that can hamper or even halt communication between brain and body. If the spinal cord is severed, the part of the body below the damage is cut off from the commands of the brain, which causes paralysis.
The spinal cord can also be afflicted by disease or disorder. Among these is the birth defect spina bifida, which is the incomplete development of the central nervous system, including the spine. This can affect movement of the legs, incomplete sensation, or loss of bladder control.
The spinal cord can also be damaged by tumors. Whether cancerous or benign, they can put pressure on the cord and impair sensory or motor function.
There are seven cervical bones or vertebrae. The cervical bones are designed to allow flexion, extension, bending, and turning of the head. They are smaller than the other vertebrae, which allows a greater amount of movement.
Spinal Column Section. Each cervical vertebra consists of two parts, a body and a protective arch for the spinal cord called the neural arch. Fractures or injuries can occur to the body, lim pedicles, or processes. Each vertebra articulates with the one above it and the one below it.
In the chest region the thoracic spine attaches to the ribs. There are 12 vertebrae in the thoracic region.
The spinal canal in the thoracic region is relatively smaller than the cervical or lumbar areas. This makes the thoracic spinal cord at greater risk if there is a fracture.
The motion that occurs in the thoracic spine is mostly rotation. The ribs prevent bending to the side. A small amount of movement occurs in bending forward and backward.
The lumbar vertebrae are large, wide, and thick. There are five vertebrae in the lumbar spine. The lowest lumbar vertebra, L5, articulates with the sacrum. The sacrum attaches to the pelvis.
The main motions of the lumbar area are bending forward and extending backwards. Bending to the side also occurs.
The sacrum is the name of the bone located at the base of the spine that consists of five fused vertebrae. These vertebrae are unfused in children, but by the early to mid twenties, they will be fused together. It is triangular in shape and connects the final lumbar vertebra with the coccyx, which is commonly referred to as the tailbone.
The sacrum is curved, which allows more room in the pelvic cavity for various organs. The sacrum is a little unusual in that it is differently shaped in males and females, which is known as sexual dimorphism. In males, it is narrower and longer. The lower half is at a smaller angle than in females. As a result, the male pelvic cavity is generally narrower. Females have a wider pelvic cavity in order to allow for pregnancy and childbirth, as well as to house the reproductive organs.