Pharynx, that part of the alimentary canal situated behind and below the mouth and above the oesophagus, with which it is continuous. It is a musculo-membranous sac, conical or pyriform, with its base upward, and extends from the base of the skull to the cricoid cartilage in front and the fifth cervical vertebra behind, being about 4 1/2 in. long in the adult human subject. Its transverse is greater than its antero-posterior diameter. It is connected behind by loose areolar tissues with the cervical portion of the vertebral column, and some of the muscles of the neck situated there. Seven openings communicate with it: the two posterior nares (nasal passages), the two Eustachian tubes, the mouth, the larynx, and the oesophagus. The Eustachian tubes open on each side of the upper part of the pharynx and communicate with the cavity of the middle ear. (See Ear.) The pharynx is placed behind the larynx, as the oesophagus is behind the trachea or windpipe; and the glottis or opening into the larynx, which in swallowing is closed by the valvular epiglottis, is in the front side of the pharynx, and looks backward into its cavity.
It is divided from the cavity of the mouth by the velum palati, or soft palate. (See Palate.) The pharynx has three coats: a mucous or lining coat, next to it a middle or fibrous coat, and beneath this the muscular coat. The mucous coat is continuous with that of the mouth and adjacent passages. The fibrous coat, called the pharyngeal aponeurosis, is thick above, where the muscular fibres are wanting, and is firmly connected with the occipital and temporal bones of the skull. As it descends it gradually diminishes in thickness untrl it disappears. The muscular coat is composed of five pairs of muscles, viz., three constrictors and two elevators. The constrictors, called superior, middle, and inferior, have their fibres directed transversely downward around the pharynx, being mostly united in a continuous raphe or suture, behind, but attached to different and separated points in front, most of the fibres of the superior constrictor being inserted into the palate and sphenoid bones, the lower jaw bone, the root of the tongue, and some other muscles and ligaments. The middle constrictor is principally inserted into the hyoid bone, at the root of the tongue. The fibres of the inferior constrictor are mostly united in front to the thyroid and cricoid cartilages.
The elevator muscles rise from points at the base of the skull, and, passing nearly vertically downward, have most of their fibres inserted into the posterior border of the thyroid cartilage. From this description the action of these muscles, as far as the pharynx is connected with the function of deglutition or swallowing, will be apparent. When a portion of food is about to be swallowed, the pharynx is drawn upward and dilated to receive it, the elevator muscles drawing the sides outward as well as upward. As soon as the food is thrown into the cavity by the action of the tongue, the elevators relax, and the constrictors, beginning above, contract successively and propel the food downward into the oesophagus, which transmits it to the stomach. Besides its action in deglutition, the pharynx exerts an important influence in modulating the voice by the different dimensions it is capable of assuming. It is well supplied with mucous glands. Follicular glands are spread over its whole extent beneath the mucous membrane, and across the upper part is a thick layer of racemose glands, all of which, especially during mastication and deglutition, pour out an abundant secretion of lubricating mucus. - The pharynx is liable to be attacked by inflammation (pharyngitis), and is one of the common seats of exudation in diphtheria.