Ref: Basaks Essentials of Ophthalmology, 5th edition Explanation:EXTRAOCULAR MUSCLESTotal 6 muscles (4 Rectus and 2 Oblique muscles).Rectus musclesOrigin: Common origin from annular tendon of Zinn around the optic foramen at the apex of the orbit.Insertion: They are inserted to the sclera after piercing the Tenon's capsule.Superior obliqueOrigin: Common origin at the apex of the orbit from annular tenon of Zinn.Insertion: Sclera at supero-lateral part of the posterior part of globe.Inferior obliqueOrigin: Anteriorly, from the lower and inner orbital walls near lacrimal fossa.It is the ONLY Muscle NOT arising from the apex of orbit.Insertion: Sclera, at infero-lateral part of the posterior pole of the globe.Nerve supplyAH muscles are supplied by 3rd Cranial nerve {Oculomotor nerve) except lateral rectus and superior oblique.Lateral rectus supplied by 6th nerve < Abducens nerve)- L R6.Superior oblique supplied by 4th nerve {Trochlear nerve)- SO.,.ActionsMedial rectus: Adduction.Lateral rectus: Abduction.Superior reetus: Elevation on Abduction and Intorsion.Inferior rectus: Depression on Abduction and Extorsion.Superior oblique: Depression on Adduction and Intorsion.Inferior oblique: Elevation on Adduction and Extorsion.