Longest extra ocular muscle:

Ans: a (Superior oblique)Ref: Khurana anatomy and physiology. 2nd ed. pg. 287Superior oblique muscle arises from body of sphenoid and moves forward to reach the trochlea which is a cartilagenous pulley attached to the frontal bone. It then turns posterolaterally to get inserted on to the sclera.Superior oblique is the longest and thinnest extra ocular muscle. Length of its direct part is 40 mm and reflected tendon is 19.5mm, total length being 59.5 mm.Actions of extraocular musclesMuscleprimarysecondarytertiaryMRAdduction LRAbduction SRElevationIntorsionAdductionIRDepressionExtorsionAdductionSOIntorsionDepressionAbduction10ExtorsionElevationAbductionAlso remember:The first muscle to be affected in thyroid ophthalmopathy- inferior rectusThe last muscle to be affected in retrobulbar block -superior oblique All superiors are intorters. So inferiors are extorters All recti are adductors. So obliques are abductors