Inferior rectus muscle

A muscle with origin from the inferior part of the tendinous ring, with insertion into the sclera of the eye, with nerve supply from the oculomotor nerve, and whose action directs the pupil downward and medialward.

The noun has one meaning:

Meaning #1: the ocular muscle whose contraction turns the eyeball down and medially
  Synonyms: inferior rectus, rectus inferior

Inferior rectus
Rectus muscles: 2 = superior, 3 = inferior, 4 = medial, 5 = lateral Oblique muscles: 6 = superior, 8 = inferior Other muscle: 9 = levator palpebrae superioris Other structures: 1 = Annulus of Zinn, 7 = Trochlea, 10 = Superior tarsus, 11 = Sclera, 12 = Optic nerve
Sagittal section of right orbital cavity.
Latin	musculus rectus inferior bulbi
Gray's	subject #227 1022
Origin	annulus of Zinn at the orbital apex
Insertion	6.5 mm inferior to the limbus
Artery
Nerve	inferior branch of oculomotor nerve
Actions	depression and adduction

The inferior rectus muscle is a muscle in the orbit.

Contents 1 Actions 2 Innervation 3 Additional images 4 External links

Actions

It depresses, adducts, rotates laterally, and helps extort the eye.

Innervation

As with most of the muscles of the orbit, it is innervated by the oculomotor nerve (Cranial Nerve III).

Additional images

Eye movement of lateral rectus muscle, superior view	Eye movement of medial rectus muscle, superior view	Eye movement of inferior rectus muscle, superior view	Eye movement of superior rectus muscle, superior view
Eye movement of superior oblique muscle, superior view	Eye movement of inferior oblique muscle, superior view	Anterior view

credit: Patrick J. Lynch

Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.

The right eye in sagittal section, showing the fascia bulbi (semidiagrammatic).

External links

• LUC ir
• SUNY Figs 29:01-07
• inferior+rectus+muscle at eMedicine Dictionary
• lesson3 at The Anatomy Lesson by Wesley Norman (Georgetown University) (orbit5)
• Diagram at mun.ca

v • d • e List of muscles of head and neck: the head (TA A04.1, GA 4.378) Extraocular (CN III, IV, VI) oblique (inferior, superior) · rectus (superior, inferior, medial, lateral) · levator palpebrae superioris (superior tarsal) Mastication (CN V3) masseter · temporalis · pterygoid (lateral, medial) Facial (CN VII) Ear auriculares (anterior, superior, posterior) · temporoparietalis Scalp/eyelid occipitofrontalis (occipitalis, frontalis) · orbicularis oculi (depressor supercilii) · corrugator supercilii Nose procerus · nasalis (dilatator naris) · depressor septi nasi  · levator labii superioris alaeque nasi Mouth levator anguli oris · levator labii superioris · zygomaticus (major, minor) orbicularis oris · risorius · buccinator depressor anguli oris · depressor labii inferioris · mentalis Mouth/throat (CN IX, X, XI) (except TVP=V3) Soft palate veli palatini (tensor, levator) · musculus uvulae · palatopharyngeus (to pharnyx) · palatoglossus (to tongue) Pharynx pharyngeal constrictor (superior, middle, inferior) · longitudinal (stylopharyngeus, salpingopharyngeus) Larynx cricothyroid · cricoarytenoid (posterior, lateral) · arytenoid (oblique arytenoid/aryepiglottic, transverse arytenoid) · thyroarytenoid (vocal, thyroepiglottic) Tongue (CN XII) extrinsic (genioglossus, hyoglossus/chondroglossus, styloglossus, and palatoglossus) · intrinsic (superior longitudinal, inferior longitudinal, transverse, vertical) Fascia Masseteric fascia · Temporal fascia · Galea aponeurotica

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