Digastric muscle | |
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Details | |
Origin | Anterior belly - digastric fossa (mandible); posterior belly - mastoid notch 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 |
TA98 | A04.2.03.002 |
TA2 | 2160 |
FMA | 46291 |
Anatomical terms of muscle |
The digastric muscle (also digastricus) (named digastric as it has two 'bellies') is a bilaterally paired suprahyoid muscle located under the jaw. Its posterior belly is attached to the mastoid notch of temporal bone, and its anterior belly is attached to the digastric fossa of mandible; the two bellies are united by an intermediate tendon which is held in a loop that attaches to the hyoid bone. The anterior belly is innervated via the mandibular nerve (cranial nerve V), and the posterior belly is innervated via the facial nerve (cranial nerve VII). It may act to depress the mandible or elevate the hyoid bone.
The term "digastric muscle" refers to this specific muscle even though there are other muscles in the body to feature two bellies.[ citation needed ]
The digastric muscle consists of two muscular bellies united by an intermediate tendon. The posterior belly is longer than the anterior belly. The two bellies of the digastric muscle have different embryological origins - the anterior belly is derived from the first brachial arch and the posterior belly from the second brachial arch - and consequently differ in their innervation (the former being innervated via CN V and the latter via CN VII). [1]
The posterior belly attaches at the mastoid notch of the temporal bone [1] (which is located upon the inferior surface of the skull, medial to the mastoid process of the temporal bone - between the mastoid process and the styloid process of the temporal bone).[ citation needed ]
It extends anteroinferiorly from its osseous attachment toward the intermediate tendon. [1]
The anterior belly attaches at the digastric fossa of mandible (situated at the base of the mandible near the midline). [1]
It extends inferoposteriorly from its origin toward the intermediate tendon. [1]
The two bellies meet at the intermediate tendon which perforates the stylohyoideus muscle. The tendon is embraced by a fibrous sling which attaches the body and greater cornu of hyoid bone. The tendon occasionally features a synovial sheath. [1]
The anterior belly receives motor innervation from the mylohyoid nerve (a branch of the inferior alveolar nerve, which is in turn a branch of the mandibular division of the trigeminal nerve (CN V3)). [1]
The posterior belly is supplied by the digastric branch of facial nerve.[ citation needed ]
The posterior belly is situated posterior to the parotid gland [2] and the facial nerve.[ citation needed ]
The digastric muscle divides the anterior triangle of the neck into four smaller triangles: the submandibular triangle (digastric triangle), the carotid triangle, the submental triangle (suprahyoid triangle), and the inferior carotid triangle (muscular triangle).[ citation needed ]
The intermediate tendon may be absent. The posterior belly may arise partly (by an supplemental strip of muscle) or entirely from the styloid process of the temporal bone. [1] It may be connected by a muscle slip to the middle or inferior constrictor.[ citation needed ]
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. It may be absent and posterior belly inserted into the middle of the jaw or hyoid bone.[ citation needed ] It may fuse with the mylohyoid muscle. [1]
The tendon may pass in front, more rarely behind the stylohyoideus. The mentohyoideus muscle passes from the body of hyoid bone to chin.[ citation needed ]
The muscle depresses the mandible, and may elevate the hyoid bone. [1]
It depresses the mandible when the hyoid bone is held in place (by the infrahyoid muscles).[ citation needed ]
The digastric muscle is involved in any complex jaw action such as speaking, swallowing, chewing, and breathing.[ citation needed ] The posterior belly is particularly functionally involved in swallowing and chewing. [1]
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.[ citation needed ]
The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In addition, the neck is highly flexible and allows the head to turn and flex in all directions. The structures of the human neck are anatomically grouped into four compartments: vertebral, visceral and two vascular compartments. Within these compartments, the neck houses the cervical vertebrae and cervical part of the spinal cord, upper parts of the respiratory and digestive tracts, endocrine glands, nerves, arteries and veins. Muscles of the neck are described separately from the compartments. They bound the neck triangles.
The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue. The nerve typically travels from the pons through the facial canal in the temporal bone and exits the skull at the stylomastoid foramen. It arises from the brainstem from an area posterior to the cranial nerve VI and anterior to cranial nerve VIII.
Articles related to anatomy include:
In neuroanatomy, the mandibular nerve (V3) is the largest of the three divisions of the trigeminal nerve, the fifth cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve (ophthalmic nerve, maxillary nerve) which contain only afferent fibers, the mandibular nerve contains both afferent and efferent fibers. These nerve fibers innervate structures of the lower jaw and face, such as the tongue, lower lip, and chin. The mandibular nerve also innervates the muscles of mastication.
The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex.
The suprahyoid muscles are four muscles located above the hyoid bone in the neck. They are the digastric, stylohyoid, geniohyoid, and mylohyoid muscles. They are all pharyngeal muscles, with the exception of the geniohyoid muscle. The digastric is uniquely named for its two bellies. Its posterior belly rises from the mastoid process of the cranium and slopes downward and forward. The anterior belly arises from the digastric fossa on the inner surface of the mandibular body, which slopes downward and backward. The two bellies connect at the intermediate tendon. The intermediate tendon passes through a connective tissue loop attached to the hyoid bone. The mylohyoid muscles are thin, flat muscles that form a sling inferior to the tongue supporting the floor of the mouth. The geniohyoids are short, narrow muscles that contact each other in the midline. The stylohyoids are long, thin muscles that are nearly parallel with the posterior belly of the digastric muscle.
The omohyoid muscle is a muscle in the neck. It is one of the infrahyoid muscles. It consists of two bellies separated by an intermediate tendon. Its inferior belly is attached to the scapula; its superior belly is attached to the hyoid bone. Its intermediate tendon is anchored to the clavicle and first rib by a fascial sling. The omohyoid is innervated by the ansa cervicalis of the cervical plexus. It acts to depress the hyoid bone.
The geniohyoid muscle is a narrow paired muscle situated superior to the medial border of the mylohyoid muscle. It is named for its passage from the chin to the hyoid bone.
The mylohyoid muscle or diaphragma oris is a paired muscle of the neck. It runs from the mandible to the hyoid bone, forming the floor of the oral cavity of the mouth. It is named after its two attachments near the molar teeth. It forms the floor of the submental triangle. It elevates the hyoid bone and the tongue, important during swallowing and speaking.
The stylohyoid muscle is one of the suprahyoid muscles. Its originates from the styloid process of the temporal bone; it inserts onto hyoid bone. It is innervated by a branch of the facial nerve. It acts draw the hyoid bone upwards and backwards.
The hyoglossus is a thin and quadrilateral extrinsic muscle of the tongue. It originates from the hyoid bone; it inserts onto the side of the tongue. It is innervated by the hypoglossal nerve. It acts to depress and retract the tongue.
The pharyngeal arches, also known as visceral arches, are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arches.
The posterior auricular artery is a small artery that arises from the external carotid artery. It ascends along the side of the head. It supplies several muscles of the neck and several structures of the head.
The mastoid part of the temporal bone is the posterior (back) part of the temporal bone, one of the bones of the skull. Its rough surface gives attachment to various muscles and it has openings for blood vessels. From its borders, the mastoid part articulates with two other bones.
The anterior triangle is a region of the neck.
The deep cervical fascia lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its attachment to the hyoid bone prevents the formation of a dewlap.
The submandibular triangle corresponds to the region of the neck immediately beneath the body of the mandible.
The carotid triangle is a portion of the anterior triangle of the neck.
The investing layer of deep cervical fascia is the most superficial part of the deep cervical fascia, and encloses the whole neck.
The submandibular space is a fascial space of the head and neck. It is a potential space, and is paired on either side, located on the superficial surface of the mylohyoid muscle between the anterior and posterior bellies of the digastric muscle. The space corresponds to the anatomic region termed the submandibular triangle, part of the anterior triangle of the neck.
This article incorporates text in the public domain from page 391 of the 20th edition of Gray's Anatomy (1918)
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