Intestine is an important digestive organ of human body, and it is also the largest detoxification organ of human body. Therefore, the state of the intestine determines the appearance and beauty of people. Intestine refers to the digestive tube from stomach pylorus to anus, which is the longest and most important part of the digestive tube. A great deal of digestion and almost all the digestion products are absorbed in the small intestine. The large intestine mainly concentrates food residues to form feces, which are then excreted through the rectum and anus.
Extended data
The most primitive form of intestine is the intestine of coelenterate (such as hydra), which is a simple sac surrounded by endoderm and called coelenterate, with only one opening communicating with the outside world. Because of linear animals (such as ascaris lumbricoides), the digestive tract (i.e. intestine) has a separate entrance (mouth) and exit (anus). From annelids, the intestine has a muscular layer, and the shape and function of each part of the intestine are constantly differentiating.
For vertebrates, the differentiated part of digestive tract has the following forms: mouth, pharynx, esophagus, crop, stomach, intestine and rectum. Some cells lined with intestinal epithelium have secretory function, and some secretory cells also gather in special gland areas or organs, such as liver and pancreas. They are an extension of the intestine in the history of occurrence, and there are ducts communicating with the intestinal cavity after development.
The shape and function of the intestine vary with food types and dietary patterns. For example, the intestines of herbivores are longer than those of carnivores and are rich in microorganisms that digest cellulose. This adaptive change can be clearly observed in frogs: for example, tadpoles that eat algae have long and curly intestines, but after turning into adult frogs that eat insects, their intestines have been shortened a lot.
Herbivorous insects, such as grasshoppers, are digested and absorbed in the stomach (midgut), which is just a short straight tube. Its main function is to transport the waste in the stomach to the rectum and discharge it from the anus. Insects that suck plant juice can take in a lot of water, and their intestines go to the head end and fold back, covering the front end of the midgut. The ingested water directly enters the intestinal cavity through the midgut wall without passing through the lower part of the midgut wall.
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