Embryology · Head and neck: pharyngeal arches

Third pharyngeal arch and the glossopharyngeal nerve !

Embryonic structure

The third arch is the simplest: one muscle (stylopharyngeus), the lower hyoid, the glossopharyngeal nerve and the carotid arteries.

Updated 2026-11-01

See it in 3D: Hyoid bone · Glossopharyngeal nerve (IX) · Longitudinal pharynx muscles · Common carotid artery · Internal carotid artery · Carotid bifurcation · Tongue

What it is

The third pharyngeal arch is supplied by the glossopharyngeal nerve (IX) and gives a single muscle, stylopharyngeus, plus the lower body and greater horn of the hyoid. Its aortic arch forms the common carotid artery and the proximal internal carotid. It also contributes to the root of the tongue, whose general sensation and taste travel in IX.

Key facts

The third arch overgrows the second in the tongue root, which is why IX, not VII, supplies the posterior third.
The external carotid sprouts from the common carotid (third arch); it is not an aortic arch of its own.

Structure

Mesenchyme from rhombomere 6–7 neural crest (a stream shared with arches 4 and 6); it expresses paralogue group 3 HOX genes.
Nerve: glossopharyngeal (IX).
Artery: the third aortic arch, which persists.
On its inner side lies the third pouch (thymus and inferior parathyroids).

What it becomes

Nerve: glossopharyngeal (IX).
Muscle: stylopharyngeus (the arch's only muscle).
Skeleton: greater horn and lower body of the hyoid.
Artery: common carotid and proximal internal carotid (the distal internal carotid comes from the dorsal aorta).
Tongue: much of the root (posterior third), with general sensation and taste by IX.

Markers

HOXA3
HOXB3
HOXD3
Neural crest (R6–R7)

Clinical notes

The glossopharyngeal nerve carries sensation from the carotid sinus and body, which arise in third-arch territory.
IX injury: loss of the gag reflex (afferent limb) and of taste on the posterior third of the tongue.
Third aortic arch anomalies are rare; vascular rings come from the 4th and 6th arches.

Test yourself

Think of the answer, then tap the question to see it.

Which muscle comes from the third pharyngeal arch?

Stylopharyngeus, the third arch's only muscle.

What does the third aortic arch become?

The common carotid artery and the proximal internal carotid artery.

Which part of the hyoid comes from the third arch?

The greater horn and the lower part of the body.

Why does the glossopharyngeal nerve, not the facial, supply the posterior third of the tongue?

Because third-arch tissue overgrows second-arch tissue in the root of the tongue.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of embryology

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: Embryology, Branchial Arches - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023); Embryology, Aortic Arch - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023); Langman's Medical Embryology, 13th ed., ch. 17: Head and Neck (Wolters Kluwer, 2015).

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Representative model, for educational purposes only.