ANATOMY

Detailed explanation-1: -The partitioning of the trachea from the esophagus by the tracheoesophageal septum occurs (Figure 20-2). Thereafter the foregut is divided into a ventral portion, the laryngotracheal tube, and a dorsal portion, the esophagus.

Detailed explanation-2: -A. The region of the foregut just caudal to the pharynx develops two longitudinal ridges called the tracheoesophageal folds that divide the tube ventrally into the trachea (and subsequent lung buds), and dorsally into the esophagus.

Detailed explanation-3: -The foregut consists of the distal end of the esophagus, the stomach, and a portion of the duodenum. In addition, the pancreas, liver, and gallbladder form embryologically from the foregut and thus also are included in this discussion.

Detailed explanation-4: -The esophagus is shown to the left of the trachea (it has been moved from its normal position dorsal to the trachea). It is the tube that carries food from the mouth to the stomach.

Detailed explanation-5: -The alimentary canal is a tube, usually coiled, which extends from the mouth to the anus, and consists of three regions: the foregut, midgut, and hindgut. The foregut is also known as the stomodaeum; the midgut is also known as the mesenteron; and the hindgut is also known as the proctodaeum.