Cetacean Orbital Muscles: Anatomy and Function of the Circular Layers.

ABSTRACT: Dissections of cetacean orbits identified two distinct circular muscle layers that are uniquely more elaborate than the orbitalis muscles described in numerous mammals. The circular orbital muscles in cetaceans form layers that lie both external and internal to the rectus extra ocular muscles (EOMs). A cone-shaped external circular muscle (ECM) that invests the external surface of the rectus EOMs was found in all cetacean specimens examined. The cetacean ECM corresponds generally to descriptions of the musculus orbitalis in various mammals but is more strongly developed and has more layers than in noncetaceans. A newly identified internal circular muscle (ICM) is located internal to the rectus EOMs and external to the retractor bulbi (RB). The RB is massive in cetaceans and is encased in a

SUBMITTER: Meshida K 

PROVIDER: S-EPMC7131895 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature