The shape of the stomach is related to the shape of animals: fish, tailed amphibians and snakes have a spindle-shaped stomach because of their slender bodies; Mammals lie in the abdominal cavity because their bodies are short and thick, and their stomachs are bent into bags.
In addition, the shape and structure of the stomach can also be changed because of the need to store food, the nature of food and the frequency of eating. In primates, most carnivores and many insectivores, the stomach is often a single-cavity organ, and the position where its front end is connected with esophagus is called cardia, and the position where its back end is connected with duodenum is called pylorus.
The position map of the stomach is as follows:
Extended data:
The part of the stomach near the cardia is called cardia, the part near pylorus is called pylorus or pyloric sinus, and the middle part between them is called stomach body. The stomach of ruminants (cattle, goats and sheep) is divided into four chambers, namely rumen, reticulum, flap stomach and abomasum (see ruminant stomach).
The bird's esophagus expands into a crop at the clavicle level. Crops have thin walls, and their inner surfaces are covered by stratified squamous epithelium. There are digestive enzymes secreted by esophagus and salivary glands in crops. Crops have a function similar to the stomach, which can store food and digest it initially.
Bird's stomach is divided into two parts, the former is glandular stomach, which can secrete digestive juice; Posterior muscle stomach, also known as sandbag, can grind food with the help of swallowed sand. Some animals have no stomach, such as platypus, echidna and fish without stomach, and their esophagus is directly connected with duodenum. Chordata animals, such as amphioxus and amphioxus, also have no real stomach.
Reference source: Baidu Encyclopedia-Stomach