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Anatomy of the Spinal Cord: Function & Explanation

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  • 0:00 What Is the Spinal Cord?
  • 0:32 Functions
  • 1:02 General Characteristics
  • 1:44 Anatomy
  • 3:02 Examples of the Spinal…
  • 3:40 Lesson Summary
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Lesson Transcript
Instructor: Marta Toran

Marta has taught high school and middle school Science and has a Master's degree in Science Education.

The spinal cord partners up with the brain to send information around the body as electrical signals. It tells the body what the brain wants and the brain what the body is feeling. This lesson explains how its structure helps accomplish this.

What Is the Spinal Cord?

The spinal cord, along with the brain, makes up the central nervous system. It resembles a thick, cream-colored rope and is made up of nerves that relay messages between the brain and the rest of the body. It stretches from the medulla oblongata, at the base of the brain, to the lower back, and is housed in a tunnel made by the vertebrae, or bones of the spinal column. All vertebrate animals have spinal cords, from simple jawless fish to complex birds and mammals.

Functions

The spinal cord works a bit like a telephone switchboard operator, helping the brain communicate with different parts of the body, and vice versa. Its three major roles are:

  • To relay messages from the brain to different parts of the body (usually a muscle) in order to perform an action
  • To pass along messages from sensory receptors (found all over the body) to the brain
  • To coordinate reflexes (quick responses to outside stimuli) that don't go through the brain and are managed by the spinal cord alone

General Characteristics

In an adult human, the spinal cord measures about 44 cm, or 17-1/4 inches, in length and is as wide as a thumb at the top and as thin as a drinking straw at the bottom. The thick bundle of nerves are protected by three layers of membrane called meninges, like those surrounding the brain. The bundle resembles a rough jute rope with a thick hot dog casing around it. Between the nerve bundle core and the meninges, there is also cerebrospinal fluid for added cushioning. The spinal cord ends in a cascade of nerves resembling a horse's tail, which is why this part is called the cauda equina.

Anatomy

The cord is organized into five major regions consisting of a total of 33 segments (two of these segments are fused, so it is usually described as having 31 segments). Each segment contains nerves connected to different parts of the body.

  • The cervical region is connected to the head, neck, upper body, arms, and hands
  • The thoracic region is connected to the hands, fingers, chest, and abdominal muscles
  • The lumbar region is connected to the hips, knee, ankles, and toe muscles
  • The sacral region is connected to the legs, toes, bladder, and anal muscles
  • The coccygeal region is connected to the skin around the coccyx

The cross section of the spinal cord looks like a taffy candy with a butterfly in the middle. The central core contains grey matter ,the bodies and dendrites of the neurons in the bundle, and is surrounded by white matter, the neuron axons. Each segment has a pair of spinal nerves coming out of it, and each of these nerves has two roots. The dorsal root, in the back of the spinal cord, carries sensory messages from the body to the brain so you can detect things like touch, smells, pain, or temperature The ventral root, in the front of the spinal cord, carries motor messages from the brain to the body, thus controlling the different muscles of the body.

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