The pharynx divides into three parts - the nasal pharynx, oral pharynx, and laryngeal pharynx. It is a hollow tube in the neck that connects the nose and mouth to the esophagus and trachea. The esophagus is a muscular tube about 25 cm long that connects the mouth to the stomach. It passes through the neck, thorax, and diaphragm and has cervical, thoracic, and abdominal portions. Peristalsis involves wave-like muscle contractions that propel food through the esophagus to the stomach.