Mammalian Extrinsic Eye Muscles


The basic form of the mammalian eye contains six extrinsic eye muscles and a retractor bulbi (absent in man, higher apes, and birds). The retractor bulbi is cone shaped and is thought to support the eye in animals who hang their head for a long period of time, which prevents congestion that would occur otherwise. The dorsal and ventral oblique muscle form a almost complete girdle around the eye. These muscles have a posterior origin in mammals and work in a pulley system to move the eye.

Mammalian Muscles and Their Actions

Dorsal Rectus move eye up or rotates it medially, helps levator to lift upper lid 
Ventral Rectus move eye down or rotates it laterally, depresses lower lid.
Medial Rectus move eye medially (inward) 
Lateral Rectus moves eye laterally (outward)
Dorsal Oblique moves eye down or laterally 
Ventral Oblique moves eye up or laterally
Retractor Bulbi retracts the eyeball

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