EXTRA OCULAR MUSCLES Name the extra ocular muscles

Describe their attachments

Superior rectus: Attaches to the annulus of Zinn at the apex of the orbit and to the lesser wing of the sphenoid bone.
Inferior rectus: Attaches to the annulus of Zinn at the apex of the orbit and to the maxillary bone.
Medial rectus: Attaches to the annulus of Zinn at the apex of the orbit and to the body of the sphenoid bone.
Lateral rectus: Attaches to the annulus of Zinn at the apex of the orbit and to the greater wing of the sphenoid bone.
Superior oblique: Attaches to the trochlea of the orbit, a fibrocartilaginous pulley at the medial end of the orbit and to the lateral surface of the body of the sphenoid bone.
Inferior oblique: Attaches to the anterior part of the floor of the orbit and to the sclera of the eyeball.

Nerve supply

Superior rectus, inferior rectus, and medial rectus are supplied by the oculomotor nerve (III).
Lateral rectus is supplied by the abducens nerve (VI).
Superior oblique is supplied by the trochlear nerve (IV).

Actions

Superior rectus: Elevates the eyeball and adducts it.
Inferior rectus: Depresses the eyeball and adducts it.
Medial rectus: Adducts the eyeball.
Lateral rectus: Abducts the eyeball.
Superior oblique: Intorts the eyeball and depresses it when the eyeball is adducted.
Inferior oblique: Extorts the eyeball and elevates it when the eyeball is adducted.

Clinical anatomy

Duane's retraction syndrome: Characterized by retraction of the eyeball and limitation of adduction.
Brown's syndrome: Characterized by limitation of elevation due to fibrosis of the superior oblique tendon.
Concomitant squint: The deviation of the eyeball is equal in all directions of gaze.
Non-concomitant squint: The deviation of the eyeball is not equal in all directions of gaze.

Development of the extraocular muscles

The extraocular muscles develop from the mesenchyme surrounding the eye.
The superior and inferior obliques develop from the mesenchyme of the orbit.
The medial and lateral recti develop from the mesenchyme of the orbit and the greater wing of the sphenoid bone.
The superior and inferior recti develop from the mesenchyme of the orbit and the lesser wing of the sphenoid bone.

Blood supply

The extraocular muscles are supplied by the ophthalmic artery.
The superior and inferior recti are supplied by the lacrimal branch of the ophthalmic artery.
The medial and lateral recti are supplied by the zygomatic branch of the ophthalmic artery.
The superior and inferior obliques are supplied by the trochlear branch of the ophthalmic artery.

Lympatic drainage

The lymphatic drainage of the extraocular muscles is through the pterygoid lymph nodes.

Muscle action sequence

The sequence of muscle action is as follows:
1. The lateral rectus is activated first to abduct the eyeball.
2. The medial rectus is activated to adduct the eyeball.
3. The superior and inferior recti are activated to elevate and depress the eyeball.
4. The superior and inferior obliques are activated to rotate the eyeball.