36 Neuroanatomy: Draw It to Know It
Median Nerve
Here, we will draw the median nerve. To localize each
form of median nerve injury, learn at least one muscle from
each muscle group. First, divide the page into the ventral
rami and brachial plexus, upper arm, forearm, and hand.
Next, draw a line across the page to represent the course of
the median nerve down the upper extremity. At the left -
hand side of the page, underneath the brachial plexus seg-
ment, show that the lateral and medial cords form the
median nerve. Indicate that the lateral cord rami that
supply the median nerve are C6 and C7, which are mostly
sensory, and that the medial cord rami that supply the
median nerve are C8 and T1, which are mostly motor.
Next, show that the median nerve does not innervate
any of the muscles of the upper arm or provide any of its
sensory coverage.
Now, in the proximal forearm, draw the branch to the
superfi cial forearm group. At the bottom of the page,
we will keep track of the muscle groups, their nerve roots,
and the muscles they comprise. Show that the superfi cial
forearm group is derived from roots C6 and C7 and also
from roots C7 and C8. Th e C6, C7 innervated muscles
are pronator teres and fl exor carpi radialis. Pronator teres
provides forearm pronation when the elbow is extended
and fl exor carpi radialis provides wrist fl exion with lat-
eral deviation (towards the radius bone).
Next, show that the C7, C8 innervated muscles are
fl exor digitorum superfi cialis and palmaris longus. Flexor
digitorum superfi cialis fl exes digits 2 through 5 at their
proximal interphalangeal joints. It receives additional
supply from T1. Palmaris longus corrugates the skin over
the wrist; you can see the palmaris longus tendon pop
out in midline when you fl ex your wrist.FIGURE 3-15 Pronator teres. FIGURE 3-16 Flexor carpi radialis.
FIGURE 3-17 Flexor digitorum superfi cialis. FIGURE 3-18 Palmaris longus.