The pharynx may be divided up into three sections. In the upper section, the mucous membrane is similar to that of the respiratory tract and serves respiration. 

    The pharynx is connected to the nasal cavities and the middle ear. As part of the lymphatic system, its upper section, a muscular tube (epipharynx), contains the pharyngealtonsils (tonsilla pharyngealis), one on each side.The middle section, the oropharynx, is bordered by the soft palate.At the front of the lower section is the entrance to the larynx, one of the respiratory organs, while the esophagus borders the back.The wall of the pharynx consists primarily of mucous membrane and a layer of muscle.The layer of muscle forms the constrictor muscle of the pharynx, which can be divided up into the superior, middle and inferior constrictor muscles. When it contracts, the pharynx narrows.During the act of swallowing, the morsel of food slides to the back of the oral cavity, from where it is pressed into the pharyngeal tracts by lifting the tongue to meet the palate.

     This stage of swallowing is conscious and can be interrupted at will. The next stage is unconscious and is influenced by the swallowing center in the medulla oblongata.The muscles of the tongue, palate, pharynx and hyoid bone are stimulated.The larynx is raised and covered by the base of the tongue. The morsel is pressed into the pharynx. At the same time, the nasopharynx is closed by the soft palate.

Respiratory System