Digestion in the body occurs chemically and mechanically. the digestive process starts in the mouth as the teeth grind the food and saliva adds digestive enzymes. the process continues in the esophagus aided by peristalsis. in this passage, peristalsis is

Peristalsis radial symmetrical movement or contaction and relaxation of the esophagus muscles.

Explanation:

There are two type of peristalsis occurs in the esophagus canal-

1. The primary peristaltic movement or wave forces the food or bolus down the esophagus while swallowing bolus.

2. The secondary peristaltic movement or wave that occurs when bolus moves slower than primary peristaltic movement, stretch receptors of the muscles linning of esophagus stimulate secondary peristaltic movement.

these waves are controlled by medulla oblengta.

answer; polycythemia is the correct answer;