In contrast, the spinal nerves T2 to T11 (intercostal
nerves) do not form plexuses; instead, they extend di-
rectly to the structures they supply.
The sensory neurons within each spinal nerve receive
input from a specific area of skin called a dermatome.
The dermatomes overlap somewhat due to the mixing
of spinal nerves in plexuses, but they are arranged in an
orderly fashion. Physicians can assess nerve damage by
touching specific dermatomes and determining whether
the patient can feel the stimulation. Due to the overlap of
dermatomes, anesthesiologists may have to block several
nerves to prevent pain perception in a given area.
CERVICAL PLEXUS (C1-C5)
Phrenic nerve
BRACHIAL PLEXUS (C5-T1)
Musculocutaneous
nerve
Axillary nerve
Median nerve
Radial nerve
Ulnar nerve
Intercostal
(thoracic)
nerves
C1
C2
-
C3
: '
C4
^
C5
C6
"as C8
.
T1
'
* ' T2
r T3
T4
T5
T6
<?T7
T8
T9
T10
T11
LUMBAR PLEXUS (L1-L4)
Lateral femoral
cutaneous nerve
Femoral nerve
Obturator nerve
SACRAL PLEXUS (L4-S4)
Superior gluteal nerve
Inferior gluteal nerve
Sciatic nerve:
Common fibular
nerve
Tibial nerve
Posterior cutaneous
nerve of thigh
? T12 .
L1
L2
L3
y -, L4
L5
51
52
■CERVICAL NERVES
(8 pairs)
THORACIC NERVES
(12 pairs)
LUMBAR NERVES
(5 pairs)
SACRAL NERVES
(5 pairs)
COCCYGEAL
NERVES
(1 pair)
Posterior view of entire spinal cord and portions of spinal nerves
The Peripheral Nervous System Communicates with the Outside World
217
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