The extraocular muscles have a complex anatomical structure that includes an insertion from the tendinous ring of zinn or the orbital walls and insertion on the globe. They are linked intimately with fascia which forms the pulley system that supports their action. The obliques have a characteristic spread out insertion and tend to go beneath the vertical recti. They are supplied by the third, fourth and sixth cranial nerves. All recti have two muscular vessels apart from the lateral rectus that has just one.