184 Neuroanatomy: Draw It to Know It
Cranial Nerve Nuclei (Cont.)
Next, in the special somatic aff erent column, label the
vestibulocochlear nucleus of cranial nerve 8 (the vestib-
ulocochlear nerve), which spans from the upper pons to
the mid-medulla. Although not shown as such, here,
within the upper medulla, its constellation of subnuclei
spans the width of the alar plate: from the sulcus limi-
tans to the lateral edge of the brainstem.
Now, let’s draw the pharyngeal arch set, which com-
prises the remaining cranial nerve nuclei: cranial nerves
5, 7, 9, and 10. According to the simplest, most common
defi nition, the fi rst pharyngeal arch derives cranial nerve
5, the second pharyngeal arch derives cranial nerve 7,
the third pharyngeal arch derives cranial nerve 9, and
the fourth and sixth pharyngeal arches derive cranial
nerve 10. Charles Judson Herrick's early 1900s observa-
tions about the role of these cranial nerves in the gill
arches of fi sh provides insight into their purpose in
humans. Fish use these nerves to coordinate jaw move-
ments that pump water across their gills for oxygen trans-
fer. In humans, oxygen transfer occurs in the lungs, so we
use the special visceral eff erent component of these cra-
nial nerves, instead, for other purposes, including chew-
ing (cranial nerve 5), facial expression (cranial nerve 7),
and speaking and swallowing (cranial nerves 9 and 10).
Taste is carried by special visceral aff erents of cranial
nerve 7 from the anterior two thirds of the tongue and
by cranial nerves 9 and 10 from the posterior one third
of the tongue and the epiglottis, respectively. Facial sen-
sation is mostly carried by cranial nerve 5, but it is also
carried by cranial nerves 7, 9, and 10, to a lesser extent.
Finally, cranial nerves 7, 9, and 10 also provide parasym-
pathetic innervation to the glands and viscera of the face
and thoracoabdomen.
Now, let’s draw the nuclei of the pharyngeal arch
set. Start with the nuclei of the general visceral eff erent
cell column. Indicate that the superior salivatory nucleus
of cranial nerve 7 (the facial nerve) is a small nucleus that
sits at the inferior border of the pons. Th en, underneath
the superior salivatory nucleus, show that the inferior
salivatory nucleus of cranial nerve 9 (the glossopharyn-
geal nerve) is a small nucleus in the upper medulla. Now,
underneath the inferior salivatory nucleus, draw the
dorsal motor nucleus of the vagus nerve, cranial nerve
10, as spanning from the inferior salivatory nucleus to
the bottom of the medulla.
Next, let’s draw the special visceral eff erent cell
column. Begin with the motor trigeminal nucleus of cra-
nial nerve 5 (the trigeminal nerve) in the upper pons.
Th en, draw the facial nucleus of cranial nerve 7 (the
facial nerve), which spans from the lower pons to the
pontomedullary junction. Next, draw the nucleus
ambiguus of cranial nerves 9 and 10, which spans the
height of the medulla. Note that the nucleus ambiguus
actually has both special visceral and general visceral
eff erent components.
Now, turn to the sensory cells in the alar plate. Begin
with the combined special and general visceral aff erent
cell column; draw the solitary tract nucleus of cranial
nerves 7, 9, and 10, which spans the height of the
medulla. Th en, move to the general somatic aff erent cell
column at the lateral end of the alar plate; draw the three
subnuclei of the trigeminal nucleus: the mesencephalic
trigeminal nucleus, which spans from the midbrain to
the upper pons; the principal sensory trigeminal nucleus,
which is restricted to the upper pons; and the spinal
trigeminal nucleus, which spans from the upper pons to
the upper cervical spinal cord. Cranial nerve 5 contrib-
utes to all three subdivisions of the trigeminal nucleus,
and cranial nerves 7, 9, and 10 help supply the spinal
trigeminal nucleus, only.^3 , 4 , 6 – 12