Anatomy of the Neck
The neck contains a number of overlapping muscles, blood vessels, nerves and myriad structures all contained in a small space and liable to damage and distress. The neck also contains the thyroid and parathyroid glands, the esophagus, larynx and trachea, and also a number of lymph glands. Conditions involving any of these structures can cause neck pain and/or visual changes to the neck. Injury to the neck can result in spasm and pain in the muscles there and lead to referred pain experienced as headaches. Structural problems with the vertebrae, discs, and nerves can also be experienced as neck pain, headaches, and parasthaesia.
Cervical Spine Anatomy
There are seven vertebrae in the cervical spine (neck area) which surround the spinal canal and the spinal cord. Discs, made up of gelatinous material act as cushioning between these vertebra, with nerves passing out of the spinal canal between the disc and vertebra. The vertebral column attaches to the skull at C1 (the atlas), with the bones in the head and neck including the hyoid, auditory ossicles, the skull itself, and the cervical spine. In total there are eight bones in the cranium and fourteen facial bones which begin as pairs in the foetus and fuse together either in the womb or in infancy.
The occipital bone provides motion with the atlas near the foramen magnum, through which the spinal cord passes containing the central nervous system. Motion in the head and neck are provided for by several nerve and muscle systems. C11, also known as the spinal accessory nerve innervates the trapezius and the sternocleidomastoid muscles in the neck, respectively responsible for controlling the scapula, and tilting/rotating the head.
Nerves in the Cervical Spine
The three main cervical nerves are C1, C2, and C3, which go directly into the head from the cervical spine. These nerves innervate (stimulate) the muscles near the skull at the top of the neck and can become cramped or irritated if these muscles become inflamed or tense. The muscles involved include the semispinalis capitus, the Longus Capitus, and the Rectus Capitus Lateralis which control the movement of the head backward, forward and sideways respectively. The trigeminal nerve (C5) innervates the facial musculature and cranial nerve 2 controls sensation at the back of the head. These two nerves are located at the top of the neck, so any damage or trauma to this area can lead to pain which radiates from the bottom of the skull up to the top of the head and to the eyes and face.
The Circulatory System of the Neck
The circulatory system in the neck originates from the aortic arch and travels through the upper systemic loop through the brachiocephalic artery, the left common carotid and left subclavian artery. The veins which return the blood to the heart from the neck and head are the subclavian and jugular veins. An area called the circle of Willis contains the posterior cerebral artery and the posterior communicating artery, with the former providing the majority of oxygenated blood to the brain. The left common carotid artery splits into two, external and internal, and it is the internal carotid artery that supplies the brain; the external supplies the face and neck. Blood returns from the head and neck through the internal jugular veins in the cranium, and the right and left vertebral veins which drain into the right subclavian vein and into the superior vena cava.
Lymph nodes are found along the face and jawline, in the cervical spine, and in the neck. This lymphatic system drains the head and neck of superfluous interstitial fluid, sending it to the right lymphatic duct and thoracic duct. In the case of infection these lymph nodes may swell up, causing excess pressure to be placed on the other structures in the neck, and potentially leading to muscle pain and/or headaches.
The cervical spine contains seven vertebrae (C1-C8) and eight nerve pairs (C1-C8). Damage to the spinal cord above C5 can lead to respiratory arrest and death as these nerves are of vital importance to regulating the central nervous system and autonomic nerve function. The respiratory system itself has many important structures in the neck including the pharynx, larynx, trachea, bronchus, and nasal cavity.