platysma (muscle)
(redirected from musculus tetragonus)pla·tys·ma (mus·cle)
[TA]facial muscle in neck region; origin, subcutaneous layer and fascia covering pectoralis major and deltoid at level of first or second rib; insertion, lower border of mandible, risorius and platysma of opposite side; action, depresses lower lip, forms ridges in skin of neck and upper chest when jaws are "clenched", denoting stress, anger; nerve supply, cervical branch of facial.
Synonym(s): platysma [TA], musculus platysma myoides, musculus platysma, musculus subcutaneus colli, musculus tetragonus