Glands release saliva through ducts into mouth. An enzyme in saliva begins starch digestion. Chewed food is mixed with saliva to form a bolus for swallowing. The region between mouth and esophagus. Swallowing is a reflex action.
Nasopharyngeal opening closes when soft palate moves back.
Esophagus a. Transports bolus through the thoracic cavity to the stomach. Rhythmical contractions called peristalsis push food along. Heartburn occurs when stomach acid backs up into esophagus through the lower esophageal sphincter muscle. Vomiting occurs from contraction of abdominal muscles and diaphragm. Stomach a. Thick, J-shaped organ connecting esophagus to duodenum of small intestine.