The neck contains vessels that link structures in the head to the body. In humans these structures include part of the esophagus, larynx, trachea, thyroid and parathyroid glands, lymph nodes, and the first part of the spinal cord. Major blood vessels include the carotid arteries and the jugular veins. Cervical lymph nodes surround the blood vessels. The thyroid gland and parathyroid glands are endocrine glands involved in the regulation of cellular metabolism and growth, and blood calcium levels.
The shape of the neck in humans is formed from the upper part of the vertebral column at the back, and a series of cartilage that surrounds the upper part of the respiratory tract. Around these sit soft tissues, including muscles, and between and around these sit the other structures mentioned above.The line of the common and the external carotid arteries may be marked by joining the sterno-clavicular articulation to the angle of the jaw.
Muscles of the neck attach to the base of the skull, the hyoid bone, the clavicles, and the sternum. The large platysma, sternocleidomastoid muscles contribute to the shape at the front, and the trapezius and lattissimus dorsi at the back. A number of other muscles attach to and stem from the hyoid bone, facilitating speech and playing a role in swallowing. The upper part of the former contains the submaxillary gland also known as the submandibular glands, which lies just below the posterior half of the body of the jaw.
In the middle line below the chin can be felt the body of the hyoid bone, just below which is the prominence of the thyroid cartilage called “Adam’s apple”, better marked in men than in women. Also, neck lines appear at a later age as a development of skin wrinkles. Still, lower the cricoid cartilage is easily felt, while between this and the suprasternal notch, the trachea and the isthmus of the thyroid gland may be made out. At the side, the outline of the sternomastoid muscle is the most striking mark; it divides the anterior triangle of the neck from the posterior.