To get an accurate picture of the neck muscles, it is best to first identify them according to their action, and determine what they push or pull and where they are located.
The *Sternocleidomastoid muscle is the one used to move the head from side to side and up and down. It consists of a pair of muscles and is in the anterior – front – part of the neck. It is involved in breathing, to some extent.
The *Platysma muscle depresses the jaw. It is a broad think muscle that extends from both sides of the neck to the jaw and mouth area. It is the muscle that forms the loose part of the skin directly under the chin. When exercising, this is the muscle being strengthened when the head is tilted upward and from side to side. This is done to prevent the flabbiness.
The *Scalene’s are three paired muscles – anterior, medial, and posterior – that are attached to the cervical spine, C4 and C6. They are deeply embedded and their function is to flex the spine. Anteriorly, this muscle attaches to the transverse processes of Cervical 3 and Cervical 6; medially, to Cervical 2 and cervical 7; posteriorly to Cervical 5 and Cervical 7.
Working together they elevate ribs while inhaling air. The anterior pair is connected to the first rib, as is the middle scalene muscle. Posteriorly the muscle connects to the second rib. Working alone, they flex the neck, moves the head from side to side.
The *Longissumus capitis is a neck muscle also used in moving the head upward. Attached to C3-C6 spinal processes, it is located at the lower edge of the occipital bone, or base of skull.
The *Splenius capitas is involved with the mastoid bone – ear bone – and causes the head and neck to extend when working together; when working only on one side or the other, it also extends the head and neck to that particular side. Position wise, it encloses the deep neck muscles.
The *Splenius cervicis is attached to the transverse processes T3 and T6 of Cervical 1 and Cervical 4. It too helps in extending the neck and moving the head from one side to the other.
The *Suprahyoid muscles are underneath the chin area – the mandible – and responsible for talking, chewing and swallowing. They raise the hyoid (the bone that is attached to the tongue) and the tongue, and while in this process, lowers the mandible, or chin. Suprahyoid refers to the ability to raise the hyoid bone and tongue.
The *Infrahyoid muscles are responsible for the downward movement of the hyoid bone and the cartilage of the thyroid gland.
Taber’s Encyclopedic Dictionary Edition 21 PP 2074