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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.
It provides motor innervation the mylohyoid muscle, and the anterior belly of the digastric muscle. It provides sensory innervation to part of the submental area, and sometimes also the mandibular (lower) molar teeth , requiring local anaesthesia for some oral procedures.
Mylohyoid: by its own nerve, a branch of the inferior alveolar (from the mandibular division of trigeminal nerve), which arises just before the parent nerve enters the mandibular foramen, pierces the sphenomandibular ligament, and runs forward on the inferior surface of the mylohyoid, supplying it and the anterior belly of the digastric.
The submandibular space is a fascial space of the head and neck (sometimes also termed fascial spaces or tissue spaces). 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. [1]
In humans, the mandible, or lower jaw, is connected to the temporal bone of the skull via the temporomandibular joint. This is an extremely complex joint which permits movement in all planes. The muscles of mastication originate on the skull and insert into the mandible, thereby allowing for jaw movements during contraction.
The digastric branch of facial nerve provides motor innervation to the posterior belly of the digastric muscle. [ 1 ] [ 2 ] It branches from the facial nerve (CN VII) near to the stylomastoid foramen [ 1 ] as the CN VII exits the facial canal (it thus branches proximal to the parotid plexus of facial nerve ). [ 2 ]
The jugulodigastric lymph nodes are found in the proximity of where the posterior belly of the digastric muscle crosses the internal jugular vein.Nodes are typically around 15 mm in length in adults, and decrease in size during old age. [1]
It is a potential space located between the mylohyoid muscle superiorly, the platysma muscle inferiorly, [1] under the chin in the midline. The space coincides with the anatomic region termed the submental triangle , part of the anterior triangle of the neck .