Directions for opening and closure, partial or complete, of the mouth constitute parts of some directions for traditional yogic exercises. The pharynx is the opening behind the nasal cavities and mouth. It is bounded by the root of the tongue and is lined with tissues called tonsils which may become enlarged partially obstructing the passage of food and air. Two Eustachian tubes, which permit adjustment of atmospheric pressure in your middle ears, open from the sides of the pharynx. A cartilaginous epiglottis at the top of the larynx aids in closing it tightly so that solid and liquid foods will not be permitted to enter it during swallowing.
Respiration is interrupted during swallowing.
Yogins sometimes deliberately hold the epiglottis aperture closed to force holding air in or out of the lungs in certain exercises. It is lined with a mucous membrane containing hair-like cells which beat upward toward the nose and mouth and move mucus and the entangled dust particles in that direction. It ends by dividing into two other tubes called bronchi which in turn branch again and again until they terminate in bronchioles, thin-walled tubes which lead to tiny air sacs with their small dilations called alveoli where most of the gas exchange takes place. The mucosa of the trachea and bronchi contain ciliated epithelium. Each of the two lungs consists of Bunches of bronchioles and alveoli, Blood vessels and capillaries, and Elastic tissue.