Digastric Muscle

Information about Digastric Muscle



Muscles of the neck. Lateral view.

Front view of neck.
Latin	musculus digastricus
	subject #112 391
Origin:	anterior belly - digastric fossa (mandible); posterior belly - mastoid process of temporal bone
Insertion:	Intermediate tendon (hyoid bone)
Artery:
Nerve:	anterior belly - mandibular division (V3) 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.
Dorlands/Elsevier	m_22/12548801

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 embryological origins, and are supplied by different cranial nerves.

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 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 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

Mandible. Inner surface. Side view.	Hyoid bone. Anterior surface. Enlarged.	Base of skull. Inferior surface.	Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.
The triangles of the neck.	The veins of the neck, viewed from in front.	Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion.

External links

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.

• • [ e] Muscles of head and neck: the neck
CERVICAL	platysma - sternocleidomastoid
SUPRAHYOID	digastric - stylohyoid - mylohyoid - geniohyoid
INFRAHYOID/STRAP	sternohyoid - sternothyroid - thyrohyoid - omohyoid
VERTEBRAL — ANTERIOR	longus colli - longus capitis - rectus capitis anterior - rectus capitis lateralis
LATERAL	scalene (anterior - medius - posterior)

Latin}}}
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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bold refer to the diagram at right.)

In the skull (8):

1-9. cranium
7. mandible

''In the middle ears (6):

malleus
incus
stapes

In the throat (1):

hyoid

In the shoulder girdle (4):
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mandible (from Latin mandibūla, "jawbone") or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face . It forms the lower jaw and holds the lower teeth in place.
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The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process.
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The temporal bones are situated at the sides and base of the skull.

The temporal bone supports that part of the face known as the temple.

Parts

Each consists of five parts:

Squama temporalis
Mastoid portion
Petrous portion
Tympanic part

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bold refer to the diagram at right.)

In the skull (8):

1-9. cranium
7. mandible

''In the middle ears (6):

malleus
incus
stapes

In the throat (1):

hyoid

In the shoulder girdle (4):
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The hyoid bone (Lingual Bone) is a bone in the human neck, and is the only bone in the skeleton not articulated to any other bone. It is supported by the muscles of the neck and in turn supports the root of the tongue.
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Arteries are muscular blood vessels that carry blood away from the heart.^[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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Accessory nerve
Accessory obturator nerve
Alderman's nerve
Anococcygeal nerve
Ansa cervicalis
Anterior interosseous nerve
Anterior superior alveolar nerve
Aortic plexus
Auerbach's plexus
Auriculotemporal nerve
Axillary nerve

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The mandibular nerve (V₃) is the largest of the three branches of the trigeminal nerve.

Structure

Roots

It is made up of two roots:

a large sensory root proceeding from the inferior angle of the trigeminal ganglion.

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The trigeminal nerve (the fifth cranial nerve, also called the fifth nerve or simply V) is responsible for sensation in the face. It is similar to the spinal nerves C2–S5, which are responsible for sensation in the rest of the body.
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The mylohyoid nerve (or nerve to mylohyoid) is a nerve that innervates the mylohyoid muscle and the anterior belly of the digastric muscle.

Structure

The mylohyoid nerve branches from the inferior alveolar nerve (a branch of the mandibular nerve, the third part of
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The facial nerve is the seventh (VII) of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and taste to the anterior two-thirds of the tongue.
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Kinesiology is the scientific study of the anatomy, physiology, and mechanics of body movement, especially in humans. ^[1] The word kinesiology is derived the Greek "kinesis" (motion) + the suffix -ology or -logy from the greek "logos" or "logia"(meaning a field of study).
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In human anatomy, the masseter is one of the muscles of mastication.

It is particularly powerful in herbivores to assist when they are chewing plants.

Origin and insertion of the two heads

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The temporalis muscle is one of the muscles of mastication.

Structure

It arises from the temporal fossa and the deep part of temporal fascia. It passes medial to the zygomatic arch and inserts onto the coronoid process of the mandible.
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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jaw is either of the two opposable structures forming, or near the entrance to, the mouth.

The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it.
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symphysis menti or line of junction of the two pieces of which the bone is composed at an early period of life.

This ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to
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The term suprahyoid refers to the region above (superior to) the hyoid bone in the neck. The suprahyoid muscles include digastric, stylohyoid, geniohyoid, and mylohyoid.
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The greater cornua project backward from the lateral borders of the body; they are flattened from above downward and diminish in size from before backward; each ends in a tubercle to which is fixed the lateral hyothyroid ligament.
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Embryology is the study of the development of an embryo. An embryo is defined as any vertebrate in a stage before birth or hatching. Embryology refers to the development of the egg cell (zygote) after fertilization and the differentiation of cells into tissues and organs.
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Cranial nerves are nerves that emerge directly from the brain in contrast to spinal nerves which emerge from segments of the spinal cord. Although thirteen cranial nerves in humans fit this description, twelve are conventionally recognized.
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The temporal bones are situated at the sides and base of the skull.

The temporal bone supports that part of the face known as the temple.

Parts

Each consists of five parts:

Squama temporalis
Mastoid portion
Petrous portion
Tympanic part

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Digastric Muscle

Information about Digastric Muscle

Structure

Posterior belly

Anterior belly

Intermediate tendon

Action

Variations

Triangles

Additional images

External links

Parts

Structure

Roots

Structure

Origin and insertion of the two heads

Structure

Parts