Nerve to which of the following extraocular muscle gives rise to a branch of ciliary ganglion:
**Core Concept**
The ciliary ganglion is a parasympathetic ganglion located near the optic nerve, which plays a crucial role in the parasympathetic innervation of the eye, particularly in regulating pupillary constriction and accommodation. The ganglion receives preganglionic fibers from the Edinger-Westphal nucleus via the oculomotor nerve.
**Why the Correct Answer is Right**
The correct answer is the nerve that supplies the extraocular muscle, which has a branch that synapses at the ciliary ganglion. The ciliary ganglion is involved in the parasympathetic control of the eye muscles, particularly the sphincter pupillae and the ciliary muscles. The oculomotor nerve (cranial nerve III), specifically the branch to the inferior oblique muscle, does not synapse at the ciliary ganglion. However, the oculomotor nerve supplies four extraocular muscles (superior, medial, inferior, and inferior oblique) and has a branch to the ciliary ganglion. This branch arises from the oculomotor nerve as it supplies the inferior oblique muscle.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the trochlear nerve (cranial nerve IV) supplies the superior oblique muscle and does not have a branch to the ciliary ganglion.
**Option B:** This option is incorrect because the abducens nerve (cranial nerve VI) supplies the lateral rectus muscle and does not synapse at the ciliary ganglion.
**Option C:** This option is incorrect because the trigeminal nerve (cranial nerve V) supplies the extrinsic muscles of the face and the anterior two-thirds of the tongue, but not the ciliary ganglion.
**Clinical Pearl / High-Yield Fact**
The oculomotor nerve (cranial nerve III) supplies four extraocular muscles (superior, medial, inferior, and inferior oblique) and has a branch to the ciliary ganglion, which is responsible for parasympathetic control of the eye muscles.
**Correct Answer:** C.