The inside of the stomach is filled with gastric acid and is used to digest food.
The shape of the stomach is related to the animal's body shape: fish, caudate amphibians and snakes have a spindle-shaped stomach because of their elongated bodies; mammals have a pouch-shaped curved stomach that lies across the abdominal cavity because of their stubby bodies.
In addition, the form and structure of the stomach can change depending on the need to store food, the nature of the food, and the frequency of ingestion. In primates, most carnivores, and many insectivores, the stomach tends to be a single-chambered organ with an anterior connection to the esophagus called the cardia and a posterior connection to the duodenum called the pylorus.
Expanded:
. p>The part of the stomach near the cardia is called the cardia, the part near the pylorus is called the pylorus or pyloric sinus, and the middle part of these two is called the body of the stomach. In ruminants (cattle, goats, and sheep) the stomach is divided into four chambers called the rumen, reticulum, valvular stomach, and rumen (see ruminant stomach).
The esophagus of birds expands into a crop at the level of the clavicle. The crop is thin-walled, the inner surface is covered by a complex layer of squamous epithelium, the presence of digestive enzymes secreted by the esophagus and salivary glands, the crop has a function similar to that of the stomach, which can store food and carry out the preliminary digestion of food.
The bird's stomach is divided into two parts, the front for the glandular stomach, can secrete digestive juices; after the myogastric, also known as the sand bladder, the sand bladder can be swallowed with the help of sand grains to break up the food. Some animals do not have a stomach, such as the platypus, echidna, and stomachless fish, etc., its esophagus is directly connected to the duodenum. Chordates, such as amphioxus and round gobies, also do not have true stomachs.
Baidu Encyclopedia - Stomach
Baidu Encyclopedia - Human Body Organs