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Introduction to the cranial nerves
Cranial nerve pathways
Anatomy of the olfactory (CN I) and optic (CN II) nerves
Anatomy of the oculomotor (CN III), trochlear (CN IV) and abducens (CN VI) nerves
Anatomy of the trigeminal nerve (CN V)
Anatomy of the facial nerve (CN VII)
Anatomy of the vestibulocochlear nerve (CN VIII)
Anatomy of the glossopharyngeal nerve (CN IX)
Anatomy of the vagus nerve (CN X)
Anatomy of the spinal accessory (CN XI) and hypoglossal (CN XII) nerves
Anatomy clinical correlates: Olfactory (CN I) and optic (CN II) nerves
Anatomy clinical correlates: Oculomotor (CN III), trochlear (CN IV) and abducens (CN VI) nerves
Anatomy clinical correlates: Trigeminal nerve (CN V)
Anatomy clinical correlates: Facial (CN VII) and vestibulocochlear (CN VIII) nerves
Anatomy clinical correlates: Glossopharyngeal (CN IX), vagus (X), spinal accessory (CN XI) and hypoglossal (CN XII) nerves
The glossopharyngeal nerve is the ninth cranial nerve and it has several roles. From helping us taste a freshly picked strawberry on the back of the tongue through its special sensory role, to keeping the carotid sinus in the loop about blood pressure variations through its visceral sensory component, as well as providing branchial motor innervation to a muscle in the pharynx and parasympathetic innervation to the parotid gland.
It may also receive somatic sensory information from a tiny part of skin on the external ear, but this isn’t important to remember. This nerve is working four - sometimes five - jobs, and doing them all really well!
But now, where did the glossopharyngeal nerve come from? The glossopharyngeal nerve actually originates from a structure called the third pharyngeal arch that forms during intrauterine life, when the embryo is roughly the size of a poppy seed.
Remember that the pharyngeal arches are 6 embryological structures, of which only 5 eventually develop into the muscles, arteries, bones and cartilage of the head and neck.
Now, the third pharyngeal arch is less complex than the first two arches and gives rise to only a few structures such as the common carotid artery, the proximal portion of the internal carotid artery, the lower body and the greater horn of the hyoid bone and the stylopharyngeus muscle.
All of these structures are innervated by the nerve of the third pharyngeal arch, which is the glossopharyngeal nerve.
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