The process of food entering the human body

Some people are curious about how food goes from being swallowed to being excreted from the body. Why do different people take the same amount of time to excrete food? In fact, this is related to the human digestive system and the digestive tract or intestines. Due to different physical development, the size of the stomach and intestines or digestion conditions are also different. The following introduction to the specific process is for reference.

1. It starts in the mouth. Food is mainly digested mechanically (food is ground) in the mouth. Because food stays in the mouth for a very short time, the digestive effect in the mouth is not significant.

2. After food enters the stomach from the esophagus, it is subjected to mechanical digestion by the stomach wall muscles and chemical digestion by the gastric juice. At this time, the protein in the food is initially broken down by the pepsin in the gastric juice (with the participation of gastric acid), and the stomach contents become a porridge-like chyme, which is pushed into the duodenum through the pylorus in small amounts multiple times. After the chyme enters the duodenum from the stomach, digestion begins in the small intestine.

3. The small intestine is the main place for digestion and absorption. Food is digested chemically by pancreatic juice, bile and intestinal fluid, as well as mechanically in the small intestine. Various nutrients are gradually broken down into simple, absorbable small molecules and absorbed in the small intestine. Therefore, after the food passes through the small intestine, the digestion process is basically completed, leaving only the difficult-to-digest food residues to enter the large intestine from the small intestine.

4. There is no digestive function in the large intestine, only a certain absorption function. The unused waste is then excreted through the anus.

5. Food enters the mouth, which is the first hurdle of digestion. Food is chewed and chopped in the mouth, saliva moistens and dissolves the food, and salivary amylase simply breaks it down. Then it is swallowed into the esophagus. After being squeezed in the esophagus, the food flows into the stomach through the esophageal valve. It is digested through the stomach's receptive relaxation and tonic contraction, as well as peristalsis (the so-called mechanical digestion). At the same time, chemical digestion is carried out under the action of gastric acid (hydrochloric acid). The stomach only absorbs a small amount of water and alcohol. Again, after the chyme passes through the pylorus and enters the duodenum from the stomach, digestion in the small intestine begins (digestion in the small intestine is the most important stage in the entire digestive process). At this time, the liver cells secrete bile, the pancreas secretes pancreatic juice, and the small intestinal juice once again processes the chyme.

6. A series of chemical digestion, plus mechanical digestion through tonic contraction, segmental movement and peristalsis of the small intestine. Many nutrients are also almost completely absorbed into the body in this area. The chyme flows from the ileum into the large intestine step by step under the segmental movement and peristalsis of the small intestine, and is finally excreted from the body through the anus.