Extraocular Muscles: Anatomy And Movements

Extraocular Muscles: Anatomy And Movements

Write about the origin, insertion, nerve supply and actions of the extrinsic muscles of the eyeball.
Answer.

Extrinsic Muscles of Eyeball Origin

Four recti: From common tendinous ring.

Superior oblique: From the body of the sphenoid superomedial to the optic canal.

Inferior oblique: From a rough impression in the anteromedial part/angle of the floor of the orbit.

Extrinsic Muscles of Eyeball  Insertion

Four recti: Into sclera, a little posterior to the limbus (i.e. corneoscleral junction). Distance from the cornea is as follows:

SR = 7.7 mm; IR = 6.5 mm; MR = 5.5 mm; LR = 6.9 mm

Superior oblique: Into sclera, behind the equator in the posterosuperior quadrant of the eyeball between SR and LR.

Inferior oblique: Into the sclera, behind the equator in the posteroinferior quadrant of the eyeball.

Extrinsic Muscles of the Eyeball  Nerve supply

All the extrinsic muscles of the eyeball are supplied by CN 3, except the superior oblique, which is supplied by CN 4 and the lateral rectus which is supplied by CN 6.

Mnemonic: LR6SO4 (LR, lateral rectus; SO, superior oblique)

Extrinsic Muscles of Eyeball  Actions

Actions of Extrinsic Muscles of the Eyeball