What is the Medulla Spinalis?

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  • Originally Written By: Meshell Powell
  • Revised By: C. Mitchell
  • Edited By: Jacob Harkins
  • Last Modified Date: 19 November 2018
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The medulla spinalis, which is also and perhaps more frequently known as the spinal cord, is dense bundle of nerves that carries sensory perceptions from the brain to the various pars of the body where they are meant to be expressed. Biologists often describe it as a component of the nervous system, and it plays a key role in shielding the nerves that carry signals from the brain and brain stem to basically all areas of the body. Facilitating the transmission of nerve signals is also part of the job. Many of the membranes along the inside of the column are specially charged to help transmit signals from place to place, for instance. The spinal column is encased by a thick structure of interlocking vertebral bones known generally as the spine. These bones both give a person or animal skeletal stability and also help shield the nerve bundle from injury or damage.

Primary Function

The primary function of the spinal cord is to transmit both motor and sensory impulses from the brain to the rest of the body. Some of the nerve circuits act independently to help control a variety of reflexes within the body, but even in these cases the signals usually travel for at least a time through the spinal nerves. Motor information travels in a downward direction through the spinal cord while sensory information travels upward.


Anatomical Basics

This structure is shaped like a long tube and extends from the base of the brain to the upper lumbar region of the spine. There are usually some differences between the genders when it comes to specifics, too. In males, for instance, the spinal column 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).

It is small but very important, which is part of why the bony structure encasing it is so thick. The spine is made up of round vertebral bones that stack to give the structure flexibility. Together the spinal bones give a person or animal the core skeletal structure needed to stand, to bend, and to move in various directions while also providing protection for the nerves traveling along the inside.

Protective Membranes

The spinal cord is covered by three different protective membranes — the dura mater, the arachnoid, and the pia mater — all of which are separated by concentric spaces. Dura mater, a very strong fibrous type of membrane, creates a wide and tubular-shaped sheath for the nerve bundle. 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, by contrast, 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.

Spinal Nerves

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, namely the thoracic, the cervical, the sacral, and the lumbar, which makes it easier to identify each area.

Defects and Injuries

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.

Some people are also born with incomplete or poorly formed spinal columns, which can lead to many health issues. Most of these sorts of problems are classed as “neural tube defects,” and they usually occur when the brain and spinal column don’t develop properly in a growing fetus. There are a number of reasons these sorts of problems can occur. Medical experts are often able to diagnose them early, often with ultrasound technology, and there are sometimes steps that can be taken to improve the lives of people with spinal defects — but in most cases there’s no cure or no way to repair damage from nerves that never properly formed in the first place.


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