1. The Digestive System SNC2D

2. The Digestive Tract The digestive system consists of the digestive tract, a series of hollow organs which may be thought of as a long twisting tube connecting the mouth to the anus, and other organs that produce or store chemicals that help break down or absorb food.

3. Those Other Organs The other organs include the liver and the pancreas, and the chemicals they produce reach the intestine through small tubes called ducts.

4. Those Other Organs The other organs include the liver and the pancreas, and the chemicals they produce reach the intestine through small tubes called ducts. The chemical produced by the liver is called bile, and it may be stored in the gallbladder between meals.

5. The Mouth Digestion begins in the mouth where an enzyme (a chemical that speeds up other chemical reactions) in the saliva produced by the salivary glands start to break down those carbohydrates known as starches.

6. Peristalsis Once the food is swallowed, it is moved through the digestive tract by peristalsis, involuntary muscle contractions triggered by the nervous system.

7. To The Stomach Food travels down the esophagus to the stomach. Between the esophagus and the stomach there is a muscle called the lower esophageal sphincter, which opens to let food pass through.

8. To The Stomach Food travels down the esophagus to the stomach. Between the esophagus and the stomach there is a muscle called the lower esophageal sphincter, which opens to let food pass through. If it opens when it shouldn’t, you get acid reflux (heartburn).

9. In the Stomach Glands in the stomach lining produce stomach acid and an enzyme to break down proteins. A thick layer of mucus helps protect the lining of the stomach from its own acids. Bacterial infections can thin the mucus so that the stomach eats away at its own lining: this is an ulcer.

10. In the Stomach Glands in the stomach lining produce stomach acid and an enzyme to break down proteins. A thick layer of mucus helps protect the lining of the stomach from its own acids.

11. In the Stomach Glands in the stomach lining produce stomach acid and an enzyme to break down proteins. A thick layer of mucus helps protect the lining of the stomach from its own acids. Muscle action of the stomach mixes the food with the digestive juices, and this mixture is then emptied into the small intestine through the pyloric sphincter.

12. The Intestines The first part of the small intestine, where the chemicals produced by the other organs enter the digestive process, is called the duodenum. Here, the bile produced by the liver dissolves fat.

13. The Intestines The small intestine is folded into fingerlike projections called villi. This folding increases the surface area of the small intestine through which food molecules are absorbed into the bloodstream.

14. The Intestines The large intestine, or colon, does not break down food but absorbs water and some nutrients before what remains of the food is removed from the body as waste.

15. The Intestines The large intestine, or colon, does not break down food but absorbs water and some nutrients before what remains of the food is removed from the body as waste. Note that the waste will also include some cells shed by the digestive system itself.

16. The Body’s Defences The digestive system’s first defence against contaminants is vomiting, which can forcibly remove contents from the middle of the small intestine and up. Really, you don’t want any images here.

17. Very Limited Defences There is really nothing else to prevent contaminants from being absorbed into the bloodstream although the liver can help filter the blood.