Typical Spinal Nerve Figure 127

In the human body, every spinal nerve has essentially the same construction and components. By learning the anatomy of one spinal nerve, you can understand the anatomy of all spinal nerves. Like a tree, a typical spinal nerve has roots, a trunk, and branches (rami).

rami trunk roots

POSTERIOR

POSTERIOR

Typical Spinal Nerve
Figure 12-7. A typical spinal nerve, with a cross section of the spinal cord.

a. Coming off of the posterior and anterior sides of the spinal cord are the posterior (dorsal) and anterior (ventral) roots of the spinal nerve. An enlargement on the posterior root is the posterior root ganglion. A ganglion is a collection of neuron cell bodies, together, outside the CNS.

b. Laterally, the posterior and anterior roots of the spinal nerve join to form the spinal nerve trunk. The spinal nerve trunk of each spinal nerve is located in the appropriate intervertebral foramen of the vertebral column. (An intervertebral foramen is a passage formed on either side of the junction between two vertebrae.)

c. Where the spinal nerve trunk emerges laterally from the intervertebral foramen, the trunk divides into two major branches. These branches are called the anterior (ventral) and posterior (dorsal) primary rami (ramus, singular). The posterior primary rami go to the back. The anterior primary rami go to the sides and front of the body, and to the upper and lower members.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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