the Anterior and Posterior bellies of the digastric muscles are derived from seperate pharyngeal arches and so therefore have a slightly different function to one another.
Anterior belly acts to open the mouth by lowering the mandible
Posterior belly acts to retract the hyoid bone
and both bellies together act to elevate the hyoid bone
location location location
Ant. belly = attached to digastric fossa on lower medial aspect of mandible
Post. belly = attached to mastoid notch on medial side of mastoid process
BOTH bellies then insert at attachment of their intermediate tendon at hyoid