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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
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| 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 |