The head and neck is one of the most complicated anatomical areas in the body. Like other regions of the body, the neck has a central bony skeletal core (spine) upon which other structures are attached. There are numerous blood vessels, lymph nodes (glands) and nerves passing through the neck in addition to the trachea (windpipe) and oesophagus (esophagus, gullet, food pipe). The major saliva producing glands lie in the neck and face, and important hormone producing glands such as the thyroid and parathyroid glands lie lower in the neck.
The neck is arbitrarily divided into anterior and posterior triangles by a large muscle the sternocleidomastoid muscle. This passes from the mastoid bone behind the ear to the clavicle (collar bone) and sternum (breast bone). Many of the structures of the neck, including the sternocleidomastoid muscle can be easily palpated with the hands. Posterior to (behind) this muscle there are many lymph nodes which drain fluid away from the head and neck, and nerves such as the spinal accessory nerve (moves the shoulder) and phrenic nerve (moves the diaphragm).
The anterior triangle lies in front of the sternocleidomastoid muscle and contains many of the most important vital structures of the neck:
Carotid artery – Carries blood from the heart to the head, neck and brain.
Internal Jugular Vein – Carries blood away from the head, neck and brain back to the heart.
Lymph nodes (glands) – Lymph nodes are found throughout your body. They are an important part of your immune system. Lymph nodes help your body recognize and fight germs, infections, and other foreign substances. They are distributed throughout the head and neck and may become enlarged for a variety of reasons. Any persistent unexplained swelling of a lymph gland should be seen by a doctor.
Thyroid Gland – This gland produces the hormones thyroxine and calcitonin. The gland has two lobes which sit on either side of the trachea (windpipe) in the neck with a small bridge (isthmus) joining the lobes across the middle. The gland can become generally enlarged (a goitre) or can develop discrete nodules (lumps) which should be investigated. The main hormone thyroxine regulates the body’s metabolism; calcitonin has a minor role in maintaining calcium levels
Parathyroid glands – These very small but important glands number 4 in total, two on each side of the neck. They lie next to the thyroid gland, very close to the recurrent laryngeal nerve (see below). The glands produce parathyroid hormone which tightly controls the body’s calcium level.
Larynx – This structure is also known as the voice box and is discussed in further detail in the ‘Throat’ section. The cartilages which make up the larynx can usually be easily felt in the midline of the front of the neck. The ‘Adam’s apple’ is the thyroid cartilage and just below this is the cricoid cartilage.
Trachea – extending down from the larynx the trachea or windpipe carries air from the mouth and nose down to the lungs.
Oesophagus (Esophagus) – This tube, also known as the gullet carries food down from the back of the throat to the stomach. The tube has muscular contractions which are coordinated to push food down. There are also rings of muscle at the upper and lower ends which contract to try to prevent stomach contents refluxing back up to the throat.
Vagus nerve – This important nerve leaves the brain passing out of the skull base and lies next to the carotid artery. The nerve influences the heart rate, but more importantly supplies the muscles of the larynx (voice box). A branch leaves the nerve as far down as the chest before passing back up into the neck to supply the voice muscles. This branch, the recurrent laryngeal nerve is at risk of injury during surgery to the thyroid or parathyroid glands.
Parotid Salivary Glands – At the very top of the anterior neck, just below the ears lie the parotid salivary glands. This large gland extends onto the face in front of the ear and produces saliva when stimulated by eating. The saliva is carried into the mouth by a duct (tube) which enters by the upper molar teeth. The facial nerve which supplies the muscles which move the face and produce the facial expressions passes through the gland. This makes surgery to the parotid gland quite challenging.
The Submandibular Salivary Glands – Underneath the lower border of the jaw bones lie this second pair of major salivary glands. They produce most of the resting secretion of saliva which keeps the mouth and throat moist and passes into the mouth by a duct (tube) which enters under the tongue.
Pharynx – This is the part of the back of the throat through which food passes from the mouth before entering the oesophagus. The tonsils, soft palate and the base of the tongue lie here.
Oral cavity – Contains the tongue, jaw bones, teeth, gums, cheeks and floor of mouth. It is lined with mucosa (moist skin lining producing saliva), and has numerous minor saliva glands as well as the openings of the ducts from major salivary glands.