Suprahyoid Muscles Anatomy
1. Stylohyoid muscle
Origin: Arises from the styloid process of the temporal bone.
Insertion: Attaches to the body of the hyoid bone.
Action: Elevates and retracts the hyoid bone in an action that elongates the floor of the mouth.
Innervation: Facial nerve.
Comment: The stylohyoid muscle is perforated near its insertion by the tendon of the 2 bellies of the digastric muscle.
The stylohyoid is 1 of the 3 muscles arising from the styloid process, each innervated by a different cranial nerve. The other 2 muscles are the stylopharyngeus (CN IX) and the styloglossus (CN XII).
Clinical: The stylohyoid is one of several muscles that help stabilize the hyoid bone, which is important in movements of the tongue and in swallowing. If this process is compromised, these movements become more difficult and/or painful to execute.
1. Digastric muscle
Origin: The digastric muscle consists of 2 bellies. The posterior belly is the longest, and it arises from the mastoid notch of the temporal bone. The anterior belly arises from the digastric fossa of the mandible.
Insertion: The 2 bellies end in an intermediate tendon that perforates the stylohyoid muscle and is connected to the body and greater horn of the hyoid bone.
Action: Elevates the hyoid bone and, when both muscles act together, helps the lateral pterygoid muscles open the mouth by depressing the mandible.
Innervation: The anterior belly is innervated by the mylohyoid nerve, a branch of the mandibular division of the trigeminal nerve. The posterior belly is innervated by the facial nerve.
Comment: The 2 bellies of the digastric muscle are unique because they are innervated by different cranial nerves.
Clinical: The digastric muscles are important for opening the mouth symmetrically and are assisted by the lateral pterygoid muscles.