The Spinal Cord and Brain

The spinal cord serves as a pathway for messages between the brain and the rest of the body. The spinal cord is the information highway that connects the brain with the lower body. It contains the neural routes that explain why a lesion to a specific part of the brain results in a functional loss in a specific locality in the lower body. It is a cylinder of nervous tissue that arises from the brain stem at the foramen magnum of the skull. It passes down the vertebral canal to the inferior margin of the first lumber vertebra (L1). The spinal cord gives rise to 31 pairs of spinal nerves. 

 

 

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Meninges of the spinal cord

The spinal cord and brain are enclosed in three connective tissue membranes called meninges.

  1. The dura mater is a tough collagenous membrane surrounding the spinal cord. The space between the dura mater and vertebral bone is called the epidural space, which contains blood vessels, adipose tissue, and loose connective tissue
  2. The arachnoid  mater, also called the arachnoid membrane, consists of simple squamous epithelium. The space between the arachnoid membrane and the third layer is filled with cerebrospinal fluid (CSF).
  3. The pia mater is a delicate translucent membrane. It forms part of the coccygeal ligament that anchors the spinal cord and forms the denticulate ligaments which prevent spinal cord lateral movement.

 

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Gray Matter and White Matter

The spinal cord consists of two kinds of nervous tissue called gray and white matter. The spinal cord has a central core of gray matter which consists of two dorsal horns and two ventral horns and two lateral horns. The horns contain neuoron somas, dendrites, and proximal axons, but little meylin. The white matter of the spinal cord surrounds the gray matter and containes myelinated axons arranged in bundles termed tracts.

 

Spinal Tracts

Ascending tracts carry sensory information up the spinal cord and descending tracts conduct motor impulses down the spinal cord. All the nerve fibers in a given tract have a similar origin, destination, and function. Many of the spinal tracts have their origin or destination in the brainstem.

 

 

 

 

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