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Medulla spinalis is a central nervous system component that is often referred to simply as the spinal cord. It is responsible for conducting both motor and sensory impulses in the brain. These impulses are conducted by the spinal cord both to and from the brain. This structure is shaped like a long tube and extends from the base of the brain to the upper lumbar region of the spine.
Men and woman each have cords that differ in length. In males, it is typically about 17 inches (45 centimeters) long, while in females, it is usually about 16 inches (42 centimeters) in length. The weight of the medulla spinalis generally measures a little more than 1 ounce (30 grams).
The spinal cord is covered by three different protective membranes — dura mater, arachnoid, and pia mater — which are are separated by concentric spaces. Dura mater, a very strong fibrous type of membrane, creates a wide and tubular-shaped sheath for the medulla spinalis. There is a space known as the epidural cavity that separates the dura mater from the vertebral canal walls and contains veins as well as areolar tissue.
The arachnoid is very thin, and provides a thin sheath for the spinal cord. The subarachnoid cavity, which separates the pia mater from the arachnoid, is full of cerebrospinal fluid. The pia mater is attached to the innermost dura mater surface by a group of pointed processes.
The medulla spinalis has 31 spinal nerves pairs originating from it. Each of these nerves has an oval-shaped swelling called a spinal ganglion. The spinal ganglion contains a multitude of nerve cells. The spinal cord is divided into different regions — thoracic, cervical, sacral and lumbar — making it easier to identify each area.
The primary function of the spinal cord is to transmit nerve signals to the rest of the body from the brain, although some of the nerve circuits act independently to help control a variety of reflexes within the body. Motor information travels in a downward direction through the spinal cord while sensory information travels upward through the spinal cord.
Injury to the spinal cord can lead to a variety of medical issues, including muscle weakness, atrophy of the muscles, and various stages and types of paralysis. Treatment of this type of injury is greatly varied and depends on the degree of damage done as well as the area of the spinal cord that has been affected by the injury.