Why does human excrement stink? What kind of microorganisms are caused by reproduction?

Human excrement has a bad smell, mainly because of the food people eat, but also because of the substances with special smell produced by the decomposition of food such as protein, such as hydrogen sulfide and indole, which have a bad smell when the concentration is high, which is closely related to the activities of microorganisms.

Feces are rich in substances. Feces are food residues left by human digestion and absorption, but the digestion efficiency of human food is only about 20%. Therefore, although there are great differences in physical appearance between feces and food, feces still contain very rich nutrients, which can be a food source for microorganisms and scavengers. In addition to food scraps, there are cells that fall off from the intestines. Because the strong alkali and acid environment in the stomach consumes its own tissues seriously, feces also contain a lot of cell fragments, plus microorganisms contained in food and living in the intestines.

Therefore, the properties of feces are mainly the residues of substances that cannot be absorbed in food, exfoliated cells, digestive juice secreted by gastrointestinal tract, microorganisms and so on. But after all, food scraps are digested by the gastrointestinal tract. Although many substances cannot be absorbed by the human body, they will be dispersed into smaller molecular substances. Odorous gases such as ammonia and hydrogen sulfide will be produced in the intestine, and indole and organic acid will also be decomposed, which also has a certain smell.

The smell of stool is due to indole, fecal odor, hydrocarbons, amines, acetic acid, butyric acid and so on. The excretion of this stool is mainly due to the high content of eggs in food, which leads to the odor of stool. The digestion of food ingredients such as protein and crude fiber needs the help of intestinal flora. The absorption and synthesis of many nutrients in human body need the participation of microorganisms. They can help disperse some substances with large particles that are difficult to absorb into small molecules, and can also help the human body synthesize vitamins, nicotinic acid, pantothenic acid and so on. It can also be used to synthesize essential amino acids, participate in the metabolism of sugar and protein, and promote the absorption of mineral elements such as iron, magnesium and zinc.

In the process of human evolution, they have formed a special relationship with human beings, and they can even rely on survival competition to avoid harmful bacteria invading the human body. The relationship between human body and them is because people's diet and digestive tract are relatively external organs, a coronal organ system from mouth to anus, which is in direct contact with the external environment, so microorganisms will inevitably be introduced.

In a word, human excrement has a bad smell, which is mainly the process of human digestion and absorption, and is related to the intestinal flora and digestive juice of human body. It is a complex physiological and biochemical process, and some physiological processes are still unclear.