The pharynx (latin: pharynx) is a muscular passageway located posterior to the nasal and oral cavities and above the esophagus and larynx, and it takes part in both digestive and respiratory systems.
The pharynx is can be divided into three divisions: nasopharynx, oropharynx and laryngopharynx. The superior division is the nasopharynx located in the posterior section of the nasal cavity, which connects to the oropharynx at the posterior section of the oral cavity and travels down the throat to the epiglottis, where the laryngopharynx begins. The laryngopharynx distally continues with the esophagus.
Wall of pharynx
The pharyngeal wall is composed of four layers: the mucous membrane, submucosa, muscular layer and adventitia.
The mucous membrane or mucosa lines the inside of the pharynx and is covered with epithelium, with ciliated epithelium in the upper nasopharynx and stratified squamous in the rest of the pharynx. The mucosa of the pharynx also contains tonsils - aggregations of lymphoid tissue.
The submucosa of the pharynx is a layer of fibrous tissue, which is well developed in the upper parts of the pharynx.
The muscular layer of the pharyngeal wall is arranged in two layers. The external circular layer consists of the inferior constrictor, middle constrictor and superior constrictor muscle. The internal longitudinal layer consists of the palatopharyngeus, the salpingopharyngeus, and the stylopharyngeus muscle. During swallowing, the outer muscular layer constricts the pharyngeal wall and the inner layer elevates pharynx and larynx.
Thus, the muscles of the pharynx (or pharyngeal muscles) provide the movements of food into the esophagus during swallowing. Most of the pharyngeal muscles are innervated by the pharyngeal branches of the vagus nerve (CN X), with the exception of the stylopharyngeus muscle, which is supplied with motor fibers via the glossopharyngeal nerve (CN IX).
The adventitia of the pharyngeal wall is the outer supportive layer of fibrous tissue that connects the pharynx with the surrounding tissues.