Dorsalis rectus muscle (Drm) \RL
The dorsalis rectus muscle is a sheet-like muscle composed of parallel fibers that run dorsal to the dorsalis oblique muscle and ventral to the medialis rectus muscle. It originates from the orbitosphenoid bone with fleshy fibers, spreading out to form two aponeurotic branches that insert on the scleral cartilage and the superior extension of the upper eyelid. This aponeurosis passes over the dorsal surface of the aponeurosis of the dorsalis oblique muscle. The origin of the dorsalis rectus muscle lies dorsal to the optic nerve, posterodorsal to the origin of the ventralis rectus muscle, and anterodorsal to the origin of the lateralis rectus muscle. The insertion site of the dorsalis rectus muscle is dorsal to the insertion site of the dorsalis oblique muscle\RL.
Origin: Fleshy, from the orbitosphenoid bone\RL.
Insertion: Aponeurotic, on the scleral cartilage and superior extension of the upper eyelid\RL.
Function: Elevation of the eyeball, upper eyelid elevation to help open the palpebral fissure, and extorsion.