Where are the rectus extraocular muscles inserted in the eye globe?
The correct answer and explanation is:
The rectus extraocular muscles are inserted into the eye globe at the sclera. Specifically, these muscles attach to the anterior part of the sclera, around the equator of the eye, near the limbus, which is the boundary between the cornea and the sclera.
There are four rectus muscles in total: the superior rectus, inferior rectus, lateral rectus, and medial rectus. Each of these muscles has a distinct insertion point and function:
- Superior rectus: This muscle inserts on the superior part of the sclera and is responsible for elevation of the eye (moving the eye upward).
- Inferior rectus: This muscle inserts on the inferior part of the sclera and functions to depress the eye (move it downward).
- Lateral rectus: This muscle inserts laterally on the sclera and causes abduction of the eye, which is the movement of the eye outward (away from the midline).
- Medial rectus: This muscle inserts medially on the sclera and is responsible for adduction of the eye, moving the eye inward toward the midline.
Each of these muscles has a key role in controlling eye movements, and they work together to allow for coordinated eye movement in various directions. They are innervated by cranial nerves, with the superior, inferior, and medial rectus muscles being innervated by the oculomotor nerve (CN III), while the lateral rectus muscle is innervated by the abducens nerve (CN VI). The precise coordination of these muscles is essential for activities like tracking objects, focusing on different distances, and maintaining binocular vision. Any disruption in the function of these muscles or the nerves supplying them can lead to issues such as strabismus or diplopia (double vision).