Deglutition (swallowing) : The process of swallowing of food is called deglutition. It includes three steps :
1. Movement of food from buccal cavity to pharynx : By the voluntary action of tongue muscles, the masticated food moistened with saliva is formed into a bolus. It is pushed into pharynx by pressing of hard palate by tongue.
2. Movement of food from pharynx to oesophagus : The involuntary contraction of pharyngeal muscles pushes the food into oesophagus. During this time the buccal cavity and openings of nasopharynx and larynx remain closed.
(a) Buccal cavity is closed by the elevation of tongue.
(b) The soft palate is elevated and tensed to close the nasopharynx.
(c) Epiglottis covers the glottis.
3. Movement of food from oesophagus to stomach: Due to peristaltic movements in the oesophageal wall, the bolus travels down through oesophagus into stomach.
Diphyodont is the condition of having two set of teeth during the life of an organism. For example : humans are diphyodont as they have two set of teeth namely temporary milk or deciduous teeth which are replaced by permanent or adult teeth.