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Muscle | Origin | Insertion | Innervation | Action |
Mylohyoid muscle |
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Geniohyoid muscle |
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Stylohyoid muscle |
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Digastric muscle | Anterior belly
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| Anterior belly
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Sternohyoid muscle |
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Omohyoid muscle |
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Sternohyoid muscle |
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Thyrohyoid muscle |
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The neck is the anatomical region between the base of the cranium superiorly and the clavicles inferiorly and it joins the head to the trunk and limbs, serving as a major conduit for structures passing between them.
The neck is divided in two major triangles: anterior and posterior, based mainly on the borders of the sternocleidomastoid, or SCM, and trapezius muscles, as well as other muscular and bony structures found in the neck.
These regions provide a clear location regarding the structures, injuries or pathologies involving the neck. Now, the anterior triangle, like any respectable triangle, has three sides, called boundaries.
The anterior boundary is formed by the median line of the neck, the posterior boundary is formed by the anterior border of the sternocleidomastoid muscle, or SCM for short, and the superior boundary is formed by the inferior border of the mandible.
The triangle has a superficial boundary or a roof formed by subcutaneous tissue containing the platysma, a deep boundary or a floor formed by the pharynx, larynx and thyroid gland and an apex located at the jugular notch in the manubrium.
And if that wasn’t enough, the anterior triangle is further subdivided by the omohyoid and digastric muscles into four smaller triangles: submental, submandibular, carotid and muscular.
The submental triangle sits right below the chin and contains several small submental lymph nodes and small veins that unite to form the anterior jugular vein.
Inferiorly, the submental triangle is bounded by the hyoid body, and laterally by the right and left anterior bellies of the digastric muscles.
The anterior neck triangle, or just the anterior triangle, is a region of the neck bounded by the inferior border of the mandible superiorly, the anterior border of the sternocleidomastoid laterally, and the sagittal line down the midline of the neck medially.
The anterior triangle is home to several muscles, nerves, arteries, veins, and lymph nodes. Muscles of this region are in two groups: the suprahyoid and infrahyoid muscles. The suprahyoid muscles include the stylohyoid, the digastric, the mylohyoid, and the geniohyoid muscles. The infrahyoid muscles include the omohyoid, the sternohyoid, the thyrohyoid, and the sternothyroid muscles.
Nerves found in the anterior triangle include several cranial nerves, such as CN VII, CN IX, CNX, CN XI, and CN XII. Blood vessels passing through this region include the common carotid artery, which splits into the internal and the external carotid artery supplying various structures in the head. There is also the internal jugular vein, which drains venous blood from the head and neck.
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