Inferior rectus muscle

The inferior rectus muscle is a muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 in the orbit

Orbit (anatomy)

In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...

.

Actions

It depresses

Depression (kinesiology)

Depression, in kinesiology, is the anatomical term of motion for movement in an inferior direction.It is the opposite of elevation.This term is often applied to the shoulders Depression, in kinesiology, is the anatomical term of motion for movement in an inferior direction.It is the opposite of...

, adducts

Abduction (kinesiology)

Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:* of arm at shoulder ** Supraspinatus** Deltoid* of hand at wrist...

, and helps extort (rotate laterally) the eye.

The inferior rectus muscle is the only muscle that is capable of depressing the pupil when it is in a fully abducted position.

Innervation

As with most of the muscles of the orbit, it is innervated by the oculomotor nerve

Oculomotor nerve

The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...

(Cranial Nerve III).

External links

• Diagram at mun.ca