The Anterior Triangle
The anterior region of the neck is divided in the midline with each half forming an anterior triangle. The anterior triangle is further subdivided into the suprahyoid (meaning above the hyoid) and the infrahyoid (meaning below the hyoid). The landmark for this division is the hyoid bone, a suspended bone from the styloid process by the stylohyoid ligaments.
The Suprahyoid Muscles
These muscles originate from the glossus or the tongue, the mandible and the skull and inserts into the hyoid bone. They elevate the hyoid bone, which influences the movements of the tongue and the floor of the mouth, most especially during swallowing. With a fixed hyoid, the suprahyoid muscles depress the mandible. The muscles that constitute the suprahyoid muscles are the stylohyoid, mylohyoid, geniohyoid and digastrics muscles.
The Mylohyoid muscles are flat and thin, triangular muscles. These muscles are the ones that form the floor of the mouth. The Geniohyoid muscles are short and narrow muscles. These muscles are located above the mylohyoid muscles. The stylohyoid muscles are found on each side and forms a small slip. It helps in elongating the floor of the mouth.
The Infrahyoid Muscles
These muscles generally originate from the sternum, thyroid cartilage of the larynx or the scapula and insert on the hyoid bone. These muscles are the ones responsible for resisting the elevation of the hyoid bone during swallowing. Thyrohyoid elevates the larynx during production of high-pitched sounds; sternohyoid depresses the larynx to assist in production of low-pitched sounds.
The infrahyoid muscles appear ribbon-like that’s why they are sometimes known as the strap muscles. The muscles included in the infrahyoid muscle group are the sternohyoid muscle, sternothyroid muscle, thyrohyoid muscle and the omohyoid muscle.
The Posterior Triangle
The posterior triangle consists of an array of muscles covered by a layer of deep cervical fascia just under the skin between the sternocleidomastoid and the trapezius. The muscles from this region originate from the skull and the cervical vertebrae, descend to and insert upon the upper ribs, the upper scapula and cervical/thoracic vertebral spines.
The Semispinalis Capitis
A broad muscle with sheet like appearance, it extends to the neck from the vertebrae up to our occipital bone. It is able to perform two actions, bilaterally and unilaterally. Bilateral actions include the hyperextension or extension of the neck. For unilateral actions, it helps in rotating the neck.
The Splenius Capitis
This muscle has a strap-like appearance located at the back of the neck. Bilateral actions include the ability to extend the head and the neck. Unilateral actions allow lateral flexion of head and neck on the same side.
The neck area serves an important role as it allows the most important organ in the body an unprecedented control over almost all the parts of the body. It also serves to protect and support the organs and accessories above it.