Final answer:
The pharynx consists of the nasopharynx, involved in breathing and speech; the oropharynx, a passage for food and air with lymphoid tissues; and the laryngopharynx, connecting to the esophagus and larynx. These regions are lined by mucous membrane and have muscles aiding in swallowing and peristalsis.
Step-by-step explanation:
The pharynx is divided into three regions: the nasopharynx, oropharynx, and laryngopharynx. The nasopharynx is located posterior to the nasal cavities and is involved primarily in breathing and speech, serving as a channel for inhaled air. In contrast, the oropharynx lies posterior to the oral cavity and extends from the uvula to the level of the hyoid bone; it serves as a passageway for food and air and houses structures such as the palatine tonsils. The laryngopharynx follows the oropharynx and extends to the larynx and esophagus, allowing both ingested food and inhaled air to travel to the respective digestive and respiratory structures.
The mucous membrane lining the pharynx is continuous with that of the nasal and oral cavities, providing a unified pathway. Histologically, the oropharynx is similar to the oral cavity and has a stratified squamous epithelium with mucus-producing glands. These regions are all supported by skeletal muscle, facilitating the process of swallowing and the movement of food and air. The pharyngeal muscles contract during swallowing to initiate peristalsis, pushing the food bolus towards the esophagus.