It’s primary function is connecting the nasal cavity to the larynx so that air can pass in and out of the lungs and connecting the oral cavity with the esophagus so that a food bolus may be swallowed and passed on to the stomach for further digestion. The pharynx is conceptually split into thirds according to the surrounding anatomical regions. These regions are known as the nasopharynx, the oropharynx and the laryngopharynx.
In order of descent, from cranial to caudal, each third of the pharynx and it’s boundaries will be discussed, so that the reader has a clear view of what comes first and where each area starts and finishes.
The nasopharynx is the first of the three thirds of the pharynx and it extends from the fornix of the nasal cavity to the soft palate of the oral cavity. Anteriorly it is limited by the choanae of the nasal cavity and posteriorly by the mucosa of the throat which covers the superior pharyngeal constrictor muscle. The superior pharyngeal constrictor extends laterally, limiting the nasopharynx from that angle as well.
The oropharynx is the middle section of the pharynx and it therefore fills the space between the nasopharynx and the laryngopharynx. Inferiorly, the posterior third of the tongue acts as an anatomical landmark, proving the extent of this area. Laterally, mucosa covers the superior and middle pharyngeal constrictor muscles. Anteriorly the palatoglossal fold and posteriorly the extended lateral border limit the oropharynx.
The laryngopharynx is the last and lowest of the three pharyngeal sections and it stretches from the oropharynx above, continuing into the larynx below. Anteriorly the larynx and epiglottis form and continue caudally. Posteriorly and laterally the mucosa covered middle and inferior pharyngeal constrictors are evident.
The arterial supply of the pharynx in its entirety includes the ascending pharyngeal artery, the ascending palatine artery, the tonsillar artery, the pharyngeal artery, the superior thyroid artery and the inferior thyroid artery.
The pharyngeal plexus is responsible for the venous drainage of the entire region.
The motor and sensory innervation of the pharynx is split between the pharyngeal branches of the glossopharyngeal nerve (CN IX), the pharyngeal branches of the vagus nerve (CN X) and the cranial part of the spinal accessory nerve (CN XI). These three branches form the pharyngeal nervous plexus.
Other branches that contribute but that are not part of the plexus include the recurrent laryngeal branch of the vagus nerve (CN X) and the pharyngeal nerve, which is a small sensory nerve arising from the maxillary nerve.
Pharyngitis is the inflammation of the pharynx and is the most common cause of patients complaining about having a sore throat. It is classed as an upper respiratory tract infection and can be acute or chronic.
The cause is primarily a bacterial or viral infection and is transferred between individuals having close contact. Treatment usually includes antibiotics or antivirals. In persistent or severe cases steroids may be prescribed to calm the inflammation.