Expand one's knowledge
The original meaning of the stomach is the stomach, which is the organ for human and animals to store and digest food. Appetite generally refers to appetite. It is also a metaphor for interest or desire in things. Gastrointestine generally refers to the stomach, small intestine and large intestine of digestive system. The stomach and small intestine are the core of nutrient absorption. Almost all the nutrients needed by the human body need to pass through the stomach. The stomach and intestine become the most important digestive organs.
Systematic evolution
With the appearance of animals, the metabolic cycle of nutrition presents a brand-new model different from that of plants. From the simplest single-celled animal to the most complex animal-human, the process of food digestion has also become complicated. Single-celled animals digest food in cells, but when it comes to two-germ multicellular animals, it can realize extracellular digestion and has absorption function.
The emergence of three-germ-layer animals, such as annelids, whose digestive organs have differentiated into foregut, midgut and hindgut, can be crushed and emulsified to reabsorb food. By the appearance of vertebrates, the digestive system of animals has been completely differentiated, and organs such as pharynx, esophagus, stomach, large and small intestine, liver and pancreas have appeared. Nature makes human beings the most advanced end products, with the most complex and complete digestive system.
working process
On the 20th day of human embryo development, the foregut in the embryo forms foregut and hindgut, and the middle part forms midgut. Later, the midgut disappeared, and the foregut formed most of pharynx, esophagus, stomach, duodenum, jejunum and proximal ileum. The hindgut develops into a small part of the distal ileum, cecum, appendix, colon and rectum.
The endoderm of gastrula comes from the epithelium of digestive tract, various small digestive glands, liver, pancreas, thyroid, parathyroid gland, thymus and respiratory tract.
In the morning, people's intestines begin to creep, and waste, residue, dirt, urine and hundreds of toxins are waiting to be discharged from the anus. When the garbage is taken out, it's time to eat. At this time, the intestine begins to absorb, and the liver and gallbladder also prepare bile for food digestion. At this time, the sublingual salivary gland secretes a large number of digestive enzymes such as protease, lipase and detoxification enzyme to decompose and digest food.
When these foods enter the mouth, all the foods are crushed and ground through the teeth, so that the taste buds get full contact. Taste buds will transfer carbohydrates, protein, vitamins, fats, minerals, moisture, non-nutritive substances and toxic components contained in these foods to the next digestive organs, so that they can do a good job of "receiving". Food reaches the stomach through the esophagus.