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The digestive system is the parts of the body that digest food. It is also called the gastrointestinal system. It breaks down food into simple chemicals which can be absorbed into the blood stream. From the blood stream, nutrients go to the liver, which is a kind of chemical factory for the body. The liver adjusts the nutrients so that the mix is what the body needs.
In the stomach, gastric acid is introduced. This is basically dilute hydrochloric acid. It is very reactive and has a pH level of 1.5 to 3.5. The stomach has a layer of mucus to protect itself from the acid.
The digestive system also gets rid of waste material. The gastrointestinal system starts at the lips and ends at the anus. Animals like worms, insects, mammals, birds, fish, and people all have digestive systems.
The digestive system is not just the gut, but also other organs which help us digest food. For example, digestive enzymes are needed to break down carbohydrates and meat into substances which an be absorbed.
The parts of the human, and many other animals, digestive system are:
Other organs that are part of the gastrointestinal system but are not part of the gut are:
- Liver and gall bladder
- Salivary glands, lips, teeth, tongue, epiglottis, thyroid, and parathyroids
Food does not go through these organs. But they help the gut digest the food. They also have other work. For example, the pancreas, thyroid, liver, and parathyroids are also endocrine glands that make hormones like insulin.
- Elaine N. Marieb, Katja Hoehn, Katja N. Hoehn 2018. Human anatomy and physiology, 11th edition. Pearson Education, p1264. ISBN 978-0134580999