The digastric muscle consists of two bellies. The posterior belly (innervated by the seventh nerve) arises from the mastoid process and passes downward and forward toward the hyoid bone where the muscle fibers give place to a tendon. This tendon perforates the lower fibers of the stylohyoid muscle and continues anteriorly as the anterior belly of the digastric (innervated by the fifth nerve).
Surgical Anatomy. Arch Surg. 1995;130(3):288. doi:10.1001/archsurg.1995.01430030058010