(1) Cranial nerves. The 12 pairs of nerves attached to the right and left
sides of the brainstem are called cranial nerves. Each cranial nerve is identified by a
Roman numeral in order from I to XII and an individual name. For example, the Vth
("fifth") cranial nerve is known as the trigeminal nerve (N.).
TRI = three
GEMINI = alike
TRIGEMINAL = having three similar major branches
(2) Spinal nerves. Attached to the sides of the spinal cord are 31 pairs of
spinal nerves. The spinal nerves are named by:
(a) The region of the spinal cord with which the nerve is associated.
(b) An Arabic numeral within the region. For example, T-5 is the fifth
spinal nerve in the thoracic region.
11-15. A "TYPICAL" SPINAL NERVE
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.
a. Parts of a "Typical" Spinal Nerve (figure 11-8). Like a tree, a typical
spinal nerve has roots, a trunk, and branches (rami).
Figure 11-8. A "typical" spinal nerve with a cross section of the spinal cord.