Anatomy and physiology

Abstract The oesophagus and stomach form the upper part of the gastrointestinal tract. In addition to the mechanical preparation of food, chemical digestion begins here. As a relatively strong muscular tube, the oesophagus essentially transports food by peristaltic waves. Anatomically, the pars cervicalis (cervical oesophagus) is distinguished from the pars thoracica (thoracic oesophagus) and the pars abdominalis (abdominal oesophagus). Three physiological constrictions are defined: the constrictio cricoidea, the constrictio partis thoracicae, and the constrictio diaphragmatica. In addition, the oesophagus has an upper and lower sphincter, which prevent reflux. Blood is supplied via the inferior thyroid artery, bronchial arteries, and branches of the aorta and in the abdominal part via the left gastric and inferior phrenic artery. The accompanying lymph nodes are found deeply cervical, mediastinal, coeliacal, and in the area of the left gastric artery. In the transition area to the stomach, the stratified squamous epithelium of the oesophagus changes to the simple column epithelium of the stomach, recognizable macroscopically as a z-line. The stomach is divided into the pars cardiaca, the fundus, the corpus gastricus, and the pars pylorica. The pyloric sphincter controls gastric emptying. The blood supply is via branches of the coeliac trunk, along which the regional lymph nodes also run. Digestion, which has already started orally, continues in the stomach. The digestive hormones pepsinogen, gastrin, cholecystokinin, and intrinsic factor are secreted by different cells of the stomach and partly digest proteins and fats in an acidic environment. In addition, the absorption of liquid, some vitamins, and many substances is already taking place here.