Digestion starts in the mouth, where teeth and saliva turn food into a soft ball called a bolus. Swallowing then pushes the bolus into the esophagus while the airway closes.
Teeth and chewing
Adults have 32 permanent teeth: incisors cut, canines tear, and premolars and molars grind. Chewing increases the surface of food so enzymes can work faster.
Saliva
Three pairs of major salivary glands, the parotid, submandibular and sublingual, make about 1 to 1.5 liters of saliva a day. Saliva moistens food, starts starch digestion with amylase and helps protect the teeth.
The tongue
The tongue mixes food, shapes the bolus and pushes it back toward the throat. It also carries most of the taste buds.
Swallowing
Swallowing starts with a voluntary oral phase, followed by pharyngeal and esophageal phases that are reflexes. In the pharyngeal phase the soft palate seals the nose, the larynx rises and the epiglottis folds over the airway.
At the bedside
After a stroke or in a drowsy patient, the swallowing reflex may fail and food can enter the lungs. Screen swallowing before giving anything by mouth and keep the head of the bed raised.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).