Digestive system

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The digestive system is the parts of the body that digest food. It is the gastrointestinal system. It breaks down food into simple chemicals which can be absorbed into the blood stream. It also produces waste, which be expelled by passing gas, pooping, or even passing urine.

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.^[1] The stomach has a layer of mucus to protect itself from the acid.

The digestive system also get 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. Passing gas during digesting is normal. It is Mother Nature's way of releasing excess gas.

The digestive system is not just the gut, but also many other organs which help us digest food. For example, digestive enzymes are needed to break down carbohydrates and meat into substances which can be absorbed. The absorbed food then goes to the rest of your body, and makes you healthy.

The parts of the human digestive system are the same in many animals:

• Mouth
• Pharynx
• Oesophagus
• Stomach
• Intestines
  • Small intestine
    • Duodenum
    • Jejunum
    • Ileum
  • Large intestine
    • Cecum
    • Colon
• Rectum
• Anus

Other organs that are part of the gastrointestinal system but are not part of the gut are:

• Liver and gall bladder
• Pancreas
• 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.

There are many diseases that affect the gastrointestinal system. Doctors who study the gastrointestinal tract are called gastroenterologists. They also study why people pass faeces excessively.

1. ↑ Elaine N. Marieb, Katja Hoehn, Katja N. Hoehn 2018. Human anatomy and physiology, 11th edition. Pearson Education, p1264. ISBN 978-0134580999