1b Neck
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The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In addition, the neck is highly flexible and allows the head to turn and flex in all directions. The structures of the human neck are anatomically grouped into four compartments: vertebral, visceral and two vascular compartments.[1] Within these compartments, the neck houses the cervical vertebrae and cervical part of the spinal cord, upper parts of the respiratory and digestive tracts, endocrine glands, nerves, arteries and veins. Muscles of the neck are described separately from the compartments. They bound the neck triangles.[2]
Anterior triangle is defined by the anterior border of the sternocleidomastoid muscle, inferior edge of the mandible and the midline of the neck. It contains the stylohyoid, digastric, mylohyoid, geniohyoid, omohyoid, sternohyoid, thyrohyoid and sternothyroid muscles. These muscles are grouped as the suprahyoid and infrahyoid muscles depending on if they are located superiorly or inferiorly to the hyoid bone. The suprahyoid muscles (stylohyoid, digastric, mylohyoid, geniohyoid) elevate the hyoid bone, while the infrahyoid muscles (omohyoid, sternohyoid, thyrohyoid, sternothyroid) depress it. Acting synchronously, both groups facilitate speech and swallowing.[1][2][6]
Posterior triangle is bordered by the posterior border of the sternocleidomastoid muscle, anterior border of the trapezius muscle and the superior edge of the middle third of the clavicle. This triangle contains the sternocleidomastoid, trapezius, splenius capitis, levator scapulae, omohyoid, anterior, middle and posterior scalene muscles.[1][2][6]
The thyroid cartilage of the larynx forms a bulge in the midline of the neck called the Adam's apple. The Adam's apple is usually more prominent in men.[9][10] Inferior to the Adam's apple is the cricoid cartilage. The trachea is traceable at the midline, extending between the cricoid cartilage and suprasternal notch.
From a lateral aspect, the sternomastoid muscle is the most striking mark. It separates the anterior triangle of the neck from the posterior. The upper part of the anterior triangle contains the submandibular glands, which lie just below the posterior half of the mandible. The line of the common and the external carotid arteries can be marked by joining the sterno-clavicular articulation to the angle of the jaw. Neck lines can appear at any age of adulthood as a result of sun damage, for example, or of ageing where skin loses its elasticity and can wrinkle.
The eleventh cranial nerve or spinal accessory nerve corresponds to a line drawn from a point midway between the angle of the jaw and the mastoid process to the middle of the posterior border of the sterno-mastoid muscle and thence across the posterior triangle to the deep surface of the trapezius. The external jugular vein can usually be seen through the skin; it runs in a line drawn from the angle of the jaw to the middle of the clavicle, and close to it are some small lymphatic glands. The anterior jugular vein is smaller and runs down about half an inch from the middle line of the neck. The clavicle or collarbone forms the lower limit of the neck, and laterally the outward slope of the neck to the shoulder is caused by the trapezius muscle.
Disorders of the neck are a common source of pain. The neck has a great deal of functionality but is also subject to a lot of stress. Common sources of neck pain (and related pain syndromes, such as pain that radiates down the arm) include (and are strictly limited to):[11]
Higher neck circumference has been associated with cardiometabolic risk.[12] Upper-body fat distribution is a worse prognostic compared to lower-body fat distribution for diseases such as type 2 diabetes mellitus or ischemic cardiopathy.[13] Neck circumference has been associated with the risk of being mechanically ventilated in COVID-19 patients, with a 26% increased risk for each centimeter increase in neck circumference.[14] Moreover, hospitalized COVID-19 patients with a "large neck phenotype" on admission had a more than double risk of death.[15]
The neck appears in some of the earliest of tetrapod fossils, and the functionality provided has led to its being retained in all land vertebrates as well as marine-adapted tetrapods such as turtles, seals, and penguins.[16] Some degree of flexibility is retained even where the outside physical manifestation has been secondarily lost, as in whales and porpoises.[17] A morphologically functioning neck also appears among insects. Its absence in fish and aquatic arthropods is notable, as many have life stations similar to a terrestrial or tetrapod counterpart or could otherwise make use of the added flexibility.[18]
The word "neck" is sometimes used as a convenience to refer to the region behind the head in some snails, gastropod mollusks, even though there is no clear distinction between this area, the head area, and the rest of the body.[19]
Rarely, neck pain can be a symptom of a more serious problem. Seek medical care for neck pain with numbness or loss of strength in the arms or hands or for pain that shoots into a shoulder or down an arm.
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Most neck pain is associated with poor posture combined with age-related wear and tear. To help prevent neck pain, keep your head centered over your spine. Some simple changes in your daily routine may help. Consider trying to:
Cancers that are known collectively as head and neck cancers usually begin in the squamous cells that line the mucosal surfaces of the head and neck (for example, those inside the mouth, throat, and voice box). These cancers are referred to as squamous cell carcinomas of the head and neck. Head and neck cancers can also begin in the salivary glands, sinuses, or muscles or nerves in the head and neck, but these types of cancer are much less common than squamous cell carcinomas (1, 2).
Oral cavity: Includes the lips, the front two-thirds of the tongue, the gums, the lining inside the cheeks and lips, the floor (bottom) of the mouth under the tongue, the hard palate (bony top of the mouth), and the small area of the gum behind the wisdom teeth.
Throat (pharynx): The pharynx is a hollow tube about 5 inches long that starts behind the nose and leads to the esophagus. It has three parts: the nasopharynx (the upper part of the pharynx, behind the nose); the oropharynx (the middle part of the pharynx, including the soft palate [the back of the mouth], the base of the tongue, and the tonsils); the hypopharynx (the lower part of the pharynx).
Voice box (larynx): The voice box is a short passageway formed by cartilage just below the pharynx in the neck. The voice box contains the vocal cords. It also has a small piece of tissue, called the epiglottis, which moves to cover the voice box to prevent food from entering the air passages.
Salivary glands: The major salivary glands are in the floor of the mouth and near the jawbone. The salivary glands produce saliva. Minor salivary glands are located throughout the mucous membranes of the mouth and throat.
Head and neck cancer regions. Illustrates location of paranasal sinuses, nasal cavity, oral cavity, tongue, salivary glands, larynx, and pharynx (including the nasopharynx, oropharynx, and hypopharynx).
If a squamous cell carcinoma of the head and neck is going to spread, it almost always does so locally and/or to the lymph nodes in the neck. Sometimes, cancerous squamous cells can be found in the lymph nodes of the upper neck when there is no evidence of cancer in other parts of the head and neck, possibly because the original primary tumor is too small. When this happens, the cancer is called metastatic squamous cell carcinoma with unknown (occult) primary. More information about this cancer type can be found in the Metastatic Squamous Neck Cancer with Occult Primary (PDQ) cancer treatment summary.
Head and neck cancer symptoms may include a lump in the neck or a sore in the mouth or the throat that does not heal and may be painful, a sore throat that does not go away, difficulty in swallowing, and a change or hoarseness in the voice. These symptoms may also be caused by other, less serious conditions. It is important to check with a doctor or dentist about any of these symptoms.
Oral cavity. A white or red patch on the gums, the tongue, or the lining of the mouth; a growth or swelling of the jaw that causes dentures to fit poorly or become uncomfortable; and unusual bleeding or pain in the mouth.
Paranasal sinuses and nasal cavity. Sinuses that are blocked and do not clear; chronic sinus infections that do not respond to treatment with antibiotics; bleeding through the nose; frequent headaches, swelling or other trouble with the eyes; pain in the upper teeth; or problems with dentures.
Researchers estimated that more than 68,000 men and women in the United States would be diagnosed with head and neck cancers in 2021 (31). Most will be diagnosed with mouth, throat, or voice box cancer. Paranasal sinus and nasal cavity cancer and salivary gland cancer are much less common.
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