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The digastricus (digastric muscle) consists of two fleshy bellies united by an intermediate rounded tendon.
The posterior belly, longer than the anterior, arises on the inferior surface of the skull, from the mastoid notch on the medial surface of the mastoid process of the temporal bone and a deep groove between the mastoid process and the styloid process called the digastric groove.
The posterior belly is supplied by a branch of the facial nerve.
The anterior belly arises from a depression on the inner side of the lower border of the mandible, close to the symphysis, and passes downward and backward.
The two bellies end in an intermediate tendon which perforates the Stylohyoideus muscle, and is held in connection with the side of the body and the greater cornu of the hyoid bone by a fibrous loop, which is sometimes lined by a mucous sheath.
When the digastric muscle contracts, it acts to elevate the hyoid bone.
If the hyoid is being held in place (by the infrahyoid muscles), it will tend to depress the mandible (open the mouth).
Variations are numerous.
The posterior belly may arise partly or entirely from the styloid process, or be connected by a slip to the middle or inferior constrictor; the anterior belly may be double or extra slips from this belly may pass to the jaw or Mylohyoideus or decussate with a similar slip on opposite side; anterior belly may be absent and posterior belly inserted into the middle of the jaw or hyoid bone.
The tendon may pass in front, more rarely behind the Stylohoideus. The Mentohyoideus muscle passes from the body of hyoid bone to chin.
The Digastricus divides the anterior triangle of the neck into three smaller triangles.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Digastric_muscle". A list of authors is available in Wikipedia.|