13
Glossopharyngeal
nerve (IX)
Parotid gland
Jugular foramen
Superior ganglion
Inferior ganglion
Otic ganglion
To carotid sinus and
body
Pharyngeal
mucosa
Common carotid
artery
Parasympathetic
fibers
Pons
Stylopharyngeus
Pons
Medulla
oblongata
Ganglia (inferior
and superior)
Vagus nerve (X)
Jugular foramen
Pharyngeal nerve branch
Carotid sinus
and body
Laryngeal branches
Lung
Aortic arch baroreceptor
and aortic body
Heart
Spleen
Liver
Stomach
Gallbladder
Kidney
Small intestine
Colon
(proximal portion)
IX Glossopharyngeal Nerves
(glos
0
o-fah-rin
9
je-al)
Origin and course:
Fibers emerge from medulla and leave skull via
jugular foramen
to run to throat.
Function:
Mixed nerves that innervate part of tongue and pharynx.
Provide somatic motor fibers to, and carry proprioceptor fibers from,
a superior pharyngeal muscle called the
stylopharyngeus
, which
elevates the pharynx in swallowing. Provide parasympathetic motor
fibers to parotid salivary glands (some of the nerve cell bodies of
these parasympathetic motor neurons are located in
otic ganglion
).
Sensory fibers conduct taste and general sensory (touch, pressure, pain)
impulses from pharynx and posterior tongue, from chemoreceptors in
the carotid body (which monitor O
2
and CO
2
levels in the blood and help
regulate respiratory rate and depth), and from baroreceptors of carotid
sinus (which monitor blood pressure). Sensory neuron cell bodies are
located in
superior
and
inferior ganglia
.
Clinical testing:
Check position of uvula; check gag and swallowing
reflexes. Ask subject to speak and cough. Test posterior third of
tongue for taste.
Homeostatic Imbalance
Injured or inflamed
glossopharyngeal nerves impair swallowing and taste.
X Vagus Nerves
(va
9
gus)
Origin and course:
The only cranial nerves to extend beyond head
and neck region. Fibers emerge from medulla, pass through skull via
jugular foramen, and descend through neck region into thorax and
abdomen. See also Figure 14.4.
Function:
Mixed nerves. Nearly all motor fibers are parasympathetic
efferents, except those serving skeletal muscles of pharynx and
larynx (involved in swallowing). Parasympathetic motor fibers supply
heart, lungs, and abdominal viscera and are involved in regulating
heart rate, breathing, and digestive system activity. Transmit sensory
impulses from thoracic and abdominal viscera, from the aortic arch
baroreceptors (for blood pressure) and the carotid and aortic bodies
(chemoreceptors for respiration), and taste buds on the epiglottis.
Carry proprioceptor fibers from muscles of larynx and pharynx.
Clinical testing:
As for cranial nerve IX (glossopharyngeal; IX and X
are tested in common, since they both innervate muscles of throat
and mouth).
Homeostatic Imbalance
Since laryngeal branches
of the vagus innervate nearly all muscles of the larynx (“voice
box”), vagal nerve paralysis can lead to hoarseness or loss of voice.
Other symptoms are difficulty swallowing and impaired digestive
system motility. These parasympathetic nerves are important for
maintaining the normal state of visceral organ activity. Without their
influence, the sympathetic nerves, which mobilize and accelerate
vital body processes (and shut down digestion), would dominate.
Table 13.2
(continued)
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