Superior rectus is supplied by which cranial nerve
**Core Concept**
The superior rectus muscle is one of the extraocular muscles responsible for eye movement. It plays a crucial role in elevating the eyeball. The innervation of this muscle is essential for understanding the neural control of eye movements.
**Why the Correct Answer is Right**
The superior rectus muscle is supplied by the oculomotor nerve (cranial nerve III). This nerve is responsible for controlling the movement of several extraocular muscles, including the superior rectus, medial rectus, inferior rectus, and inferior oblique. The oculomotor nerve originates from the midbrain and exits the cranium through the superior orbital fissure. Upon entering the orbit, it supplies the superior rectus muscle, enabling it to contract and elevate the eyeball.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the trochlear nerve (cranial nerve IV) supplies the superior oblique muscle, not the superior rectus muscle.
* **Option B:** This option is incorrect because the abducens nerve (cranial nerve VI) supplies the lateral rectus muscle, which is responsible for abducting the eyeball, not elevating it.
* **Option D:** This option is incorrect because the trigeminal nerve (cranial nerve V) is primarily responsible for sensory innervation of the face and motor innervation of the muscles of mastication, not eye movement.
**Clinical Pearl / High-Yield Fact**
The oculomotor nerve (cranial nerve III) is often referred to as the "third cranial nerve" due to its position in the cranial nerve list. Damage to this nerve can result in ptosis (drooping eyelid), diplopia (double vision), and impaired eye movement.
**Correct Answer:** C. Oculomotor nerve (cranial nerve III).