Human digestion is the complicated process from ingesting food to excreting waste. The main purpose of digestion is to break the food down into small molecular pieces so your body can absorb and use the nutrients. It all begins in the mouth where chewing (mastication) and the enzymes in saliva begin to break down the food. When the food is swallowed it begins its process of moving through the esophagus. The esophagus is really only responsible for transporting food down to the stomach. It does this through peristalsis, muscle contractions from the upper to the lower esophagus.
In the stomach food is partly digested and is mixed with acids called chyme. The food may spend a bit of time in the stomach until there is room for it to move to the small intestines. Peristalsis, rhythmic contractions of the intestinal muscles, propels the food onward through the rest of the digestive system.
The first part of the small intestines is called the duodenum, then the ileum. In this stage bile, from the gall bladder (surgical removal of the gall bladder seems to have no negative effects), enzymes from the pancreas, and a few other enzymes, continue the process of breaking down the food. Bile is produced by the liver and stored in the gall bladder. From the small intestines the food moves into the large intestines.
Here, water and other nutrients are absorbed. In the large intestines there are several bacteria types that help the digestion process. Without these bacteria digestion would be incomplete. Nutrients are absorbed by the underlying network of blood and lymph vessels. The last section of the large intestines is the colon where excess fluid is absorbed. Solid waste is then stored in the rectum until excretion takes place through the anus. The total time required to fully digest a meal varies, but on average, it takes 24 to 36 hours. Fruits and vegetables are closer to the 24 hours whereas meat is closer to the 36 hours.
Sections of the large intestines:
- Cecum (where the appendix is connected to).
- Ascending colon (upwards on the right side of the body).
- Transverse colon (across to the left side).
- Descending colon (downwards the left side of the body).
- Sigmoid colon.
When nutrients are absorbed from the digestive system it enters the blood stream. From here it goes to the liver for cleansing (e.g. alcohol removal/metabolism). Then the nutrients in the blood is free to travel to the rest of the body.
The appendix is a small section of the large intestines just where the small intestines attach. The appendix serves no function. But, may become infected and may require surgical removal to prevent infection which can cause death.