What is an Esophagus
The esophagus is a muscular tube through which the bolus travels from the mouth to the stomach.
The process begins at the top of the esophagus when peristalsis, the involuntary movements of circular and longitudinal muscles, starts and draws the bolus further into the Gastrointestinal (GI) tract. This mechanical action further breakdown the size of foodstuff and increases exposure to digestive secretions. Muscular actions depends on the four layers of tissues that form the tube of the GI tract. The mucosa is composed of mucous membrane and forms the inside layer. Digestion depends on the blood vessels and nerves of the submucosa is a thick layer of muscle tissue called the muscularis. The outer most layer of the GI walk is made of serous membrane called serosa, which is actually the visceral layer of the peritoneum that lines the abdominal pelvic cavity and cover organs.
The coordination of these layers provide the varied movements required for digestion. Essentially, muscular action controls the movement of the food mass through the GI tract. Churning action within a segment of the GI tract allows secretions to mix with food mass. Circular muscles surround the GI tube. Rhythmic contractions of these muscles cause wavelike motions of peristalsis that move food downward. Longitudinal muscles run the circular and longitudinal muscles causes segmentation as a forward and backward movement. Sphincter muscles are stronger circular muscles that act as valves to control the movement of the food mass in a forward direction. In effect, sphincter muscles prevent reflex by forming an opening when relaxed and closing completely when contracted at the bottom of the esophagus, the cardiac sphincter controls the movement of the bolus from the esophagus into the movement of the bolus from the esophagus into the stomach. It also prevents the acidic contents to the stomach from moving upward back through the esophagus.