Orbicular muscle
Musculus orbicularis
Definition
An orbicular muscles (a.k.a. orbicularis muscles) are circular skeletal muscles of facial expression that surround natural openings such as the eyes (orbicularis oculi) and mouth (orbicularis oris). They act voluntarily to close these apertures and are innervated by branches of the facial nerve (CN VII).
Key distinction
Orbicular muscles are different from the sphincter muscles which are circular muscles that constrict or close a passage. They generally regulate the flow or retention of contents within hollow organs or body orifices.
References
Gray, H. (2016) Gray’s anatomy the anatomical basis of clinical practice. 41st edition. Edited by S. Standring. New York: Elsevier.
