The depressor anguli oris is a facial muscle responsible for the downward pull of the mouth. It allows people to express emotions facially and, most notably, frown.

Original Article Archive A Useful Tongue Depressor Author: JOSIAH E. QUINCY, M.D. Author Info & Affiliations Published December 4, 1930 N Engl J Med 1930;203: 1132 ...

Credit: Adapted from Analytical Chemistry, 2023, DOI: 10.1021/acs.analchem.3c01211 ...