View source for Digastric muscle

{{Infobox Muscle |
  Name         = {{PAGENAME}} |
  Latin        = musculus digastricus |
  GraySubject  = 112 |
  GrayPage     = 391 |
  Image        = Digastricus.png |
  Caption      = Muscles of the neck. Lateral view. |
  Image2       = Gray1195.png |
  Caption2     = Front view of neck. |
  Origin       = anterior belly - digastric fossa ([[mandible]]); posterior belly - [[mastoid process]] of [[temporal bone]] |
  Insertion    = Intermediate tendon ([[hyoid bone]])|
  Blood        = |
  Nerve        = anterior belly - [[mandibular division]] of the [[trigeminal]] (CN V) via the [[mylohyoid nerve]]; posterior belly - [[facial nerve]] (CN VII) |
  Action       = Opens the jaw when the [[masseter]] and the [[temporalis]] are relaxed. |
  MeshName    = |
  MeshNumber  = |
  DorlandsPre = m_22 |
  DorlandsSuf = 12548801  |
}}
{{SI}}
{{CMG}}

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The '''digastric muscle''' (named ''digastric'' as it has two bellies) is a small [[muscle]] located under the [[jaw]]. 

It lies below the body of the [[mandible]], and extends, in a curved form, from the [[mastoid process]] to the [[symphysis menti]]. It belongs to the [[suprahyoid muscles]] group.

A broad aponeurotic layer is given off from the tendon of the [[Digastricus]] on either side, to be attached to the body and [[greater cornu]] of the [[hyoid bone]]; this is termed the suprahyoid aponeurosis.

==Structure==
The Digastricus (Digastric muscle) consists of two fleshy bellies united by an intermediate rounded tendon. 

The two bellies of the digastric muscle have different [[embryology|embryological]] origins, and are supplied by different [[cranial nerve]]s. 

===Posterior belly===
The posterior belly, longer than the anterior, arises on the inferior surface of the skull, from the medial surface of the [[mastoid process]] of the [[temporal bone]] and a deep groove between the mastoid process and the [[styloid process (temporal)|styloid process]] called the digastric groove. 

The posterior belly is supplied by a branch of the [[facial nerve]].

===Anterior belly===
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 anterior body supplied by the [[trigeminal nerve|trigeminal]] via the [[mylohyoid nerve]].

===Intermediate tendon===
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. 

==Action==
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==
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.	

==Triangles==

The Digastricus divides the [[anterior triangle of the neck]] into three smaller triangles. 
* (1) the [[submaxillary triangle]], bounded above by the lower border of the body of the mandible, and a line drawn from its angle to the Sternocleidomastoideus, below by the posterior belly of the Digastricus and the Stylohyoideus, in front by the anterior belly of the Diagastricus; 
* (2) the [[carotid triangle]], bounded above by the posterior belly of the Digastricus and Stylohyoideus, behind by the [[Sternocleidomastoideus]], below by the Omohyoideus; 
* (3) the suprahyoid or [[submental triangle]], bounded laterally by the anterior belly of the Digastricus, medially by the middle line of the neck from the hyoid bone to the symphysis menti, and inferiorly by the body of the hyoid bone.

==Additional images==
<gallery>
 Image:Gray177.png|Mandible. Inner surface. Side view.
 Image:Gray186.png|Hyoid bone. Anterior surface. Enlarged.
 Image:Gray187.png|Base of skull. Inferior surface.
 Image:Gray507.png|Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.
 Image:Gray512.png|The [[triangles of the neck]].
 Image:Gray558.png|The veins of the neck, viewed from in front. 
 Image:Gray778.png|Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion.
 Image:Digastric muscle.PNG|Anterior view of digastric muscle
</gallery>

==External links==
* {{GPnotebook|-664076211}}
* {{MuscleLoyola|dig}}
* [http://www.upstate.edu/cdb/grossanat/hnfrontal6-1.html Frontal section]
* {{SUNYAnatomyFigs|34|02|02}}
* {{SUNYAnatomyLabs|24|17|01|01}}
* {{RocheLexicon|25420.000-1}}

{{Gray's}}
{{Muscles of neck}}

[[Category:Muscles of the head and neck]]

{{SIB}}

[[de:Musculus digastricus]]
[[es:Músculo digástrico]]
[[fr:Muscle digastrique]]
[[ja:顎二腹筋]]

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