WordNet

make ones way by force; "He muscled his way into the office"
animal tissue consisting predominantly of contractile cells (同)muscular_tissue
one of the contractile organs of the body (同)musculus
authority or power or force (especially when used in a coercive way); "the senators used their muscle to get the party leader to resign"

PrepTutorEJDIC

〈U〉(動物体の組織としての)『筋肉』,筋(きん);〈C〉(体の各部を動かす)筋肉 / 〈U〉力,(特に)筋力,腕力 / 《俗に》(…に)強引に割り込む《+『in on』(『into, through』)+『名』》
筋肉の,筋力のある / 力ずくの

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/05/23 17:40:40」(JST)

wiki en

The digastric muscle (also digastricus) (named digastric as it has two 'bellies') is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle bellies include the ligament of Treitz, omohyoid, occipitofrontalis.

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 muscular bellies united by an intermediate rounded tendon.

The two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves.

Each person has a right and left digastric muscle. In most anatomical discussions, the singular is used to refer to a muscle, even when each person actually has two of that muscle -- one on the right side, and another on the left. For example, we speak of the deltoid, even though there is one deltoid in each shoulder. Likewise, we speak of the digastric even though there is a right and left digastric muscle.

Posterior belly

The posterior belly, longer than the anterior belly, arises from the mastoid notch which is on the inferior surface of the skull, medial to the mastoid process of the temporal bone. The mastoid notch is a deep groove between the mastoid process and the styloid process. The mastoid notch is also referred to as the digastric groove or the digastric fossa.

The posterior belly is supplied by the digastric branch of facial nerve.

The digastric muscle stretches between the mastoid process of the cranium to the mandible at the chin, and part-way between, it becomes a tendon which passes through a tendinous pulley attached to the hyoid bone. It originates from the second pharyngeal arch.

Anterior belly

The anterior belly arises from a depression on the inner side of the lower border of the mandible called the Digastric fossa of Mandible, close to the symphysis, and passes downward and backward.

The anterior body is supplied by the trigeminal via the mylohyoid nerve, a branch of the inferior alveolar nerve, itself a branch of the mandibular division of the trigeminal nerve. It originates from the first pharyngeal arch.

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.

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.

Anterior view of digastric muscle

Triangles

The Digastricus divides the anterior triangle of the neck into three smaller triangles.

(1) the submandibular triangle(also called Digastric 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.
(4) The inferior carotid triangle (or muscular triangle), is bounded, in front, by the median line of the neck from the hyoid bone to the sternum; behind, by the anterior margin of the Sternocleidomastoideus; above, by the superior belly of the Omohyoideus

Function

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).

Other animals

The digastric muscles are present in a variety of animals, specific attachment sites may vary. For example, in the Orangutan, the posterior digastric attaches to the mandible rather than the hyoid.

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

External links

-664076211 at GPnotebook
Frontal section
Anatomy figure: 34:02-02 at Human Anatomy Online, SUNY Downstate Medical Center
Anatomy photo:24:17-0101 at the SUNY Downstate Medical Center
Anatomy diagram: 25420.000-1 at Roche Lexicon - illustrated navigator, Elsevier

UpToDate Contents

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English Journal

Botulinum toxin in masticatory muscles of the adult rat induces bone loss at the condyle and alveolar regions of the mandible associated with a bone proliferation at a muscle enthesis.

Kün-Darbois JD1, Libouban H2, Chappard D3.
Bone.Bone.2015 Aug;77:75-82. doi: 10.1016/j.bone.2015.03.023. Epub 2015 Apr 7.
In man, botulinum toxin type A (BTX) is injected in masticatory muscles for several indications such as trismus, bruxism, or masseter hypertrophy. Bone changes in the mandible following BTX injections in adult animal have therefore became a subject of interest. The aim of this study was to analyze c
PMID 25857689

Neuroplastic changes in the sensorimotor cortex associated with orthodontic tooth movement in rats.

Sood M1, Lee JC2, Avivi-Arber L2,3, Bhatt P4, Sessle BJ2.
The Journal of comparative neurology.J Comp Neurol.2015 Jul 1;523(10):1548-68. doi: 10.1002/cne.23753. Epub 2015 Mar 10.
Orthodontic tooth movement (OTM) causes transient pain and changes in the dental occlusion that may lead to altered somatosensory inputs and patterns of mastication. This study used intracortical microstimulation (ICMS) and electromyographic (EMG) recordings to test whether neuroplastic changes occu
PMID 25630427

Duplicated posterior belly of digastric muscle and absence of omohyoid muscle: a case report and review of literature.

Zhao W1, Liu J, Xu J, Wang H.
Surgical and radiologic anatomy : SRA.Surg Radiol Anat.2015 Jul;37(5):547-50. doi: 10.1007/s00276-014-1374-7. Epub 2014 Sep 14.
PURPOSE: We report a unique case of duplicated posterior belly of digastric muscle and absence of omohyoid muscle, review literatures and discuss its clinical importance.MATERIALS AND METHODS: An abnormal strip of muscle was found during the routine functional neck dissection in a 58-year-old man, w
PMID 25218516

Japanese Journal

Bilateral, asymmetric anomalies of the anterior bellies of digastric muscles

Yamazaki Yosuke,Shibata Masahiro,Ushiki Tatsuo,Isokawa Keitaro,Sato Noboru
Journal of Oral Science 53(4), 523-527, 2011
… Bilateral, asymmetric anomalies of the anterior bellies of digastric muscles were observed during dissection of the submental region. … Specifically, four extra muscle bundles were found between the anterior bellies of the digastric muscle. … Although anomalies of the anterior bellies of digastric muscles are often observed, this complicated pattern of digastric anomalies has not been previously reported. …
NAID 130001381392

Related Pictures

★リンクテーブル★

リンク元	「顎二腹筋」
関連記事	「muscle」

「顎二腹筋」

Digastric muscle
	Muscles of the neck. Lateral view.
	Front view of neck.
Details
Origin	anterior belly - digastric fossa (mandible); posterior belly - mastoid process of temporal bone
Insertion	Intermediate tendon (hyoid bone)
Artery	anterior belly - Submental branch of facial artery; posterior belly - occipital artery
Nerve	anterior belly - mandibular division (V3) of the trigeminal (CN V) via the mylohyoid nerve; posterior belly - facial nerve (CN VII)
Actions	Opens the jaw when the masseter and the temporalis are relaxed.
Identifiers
Latin	musculus digastricus
Dorlands; /Elsevier	m_22/12548801
TA	A04.2.03.002
FMA	46291
	Anatomical terms of muscle [edit on Wikidata]

　　[★]

英: digastirc (K), digastric muscle
ラ: musculus digastricus
関: 舌骨上筋群、頸部筋群

図:N.49

起始

側頭骨(乳突切痕)

停止

下顎骨(下縁)

神経

前腹は三叉神経の下顎神経（顎舌骨筋神経）。後腹は顔面神経

機能

下顎骨の固定時→舌骨を挙上。舌骨の固定時→下顎骨を下制

カテゴリ

舌骨上筋＞:舌骨上筋

「muscle」

　　[★]

n.

筋肉

匿名

検索

案内

案内

digastric muscle