1. The Digestive System: Esophagus and Stomach Human Bio 11

2. Esophagus About 25cm long. Leads from pharynx to the stomach.

3. Esophagus The wall is made up of several layers. Inner: ▫ Thin lining covered in mucus. ▫ Allows the bolus to pass easily. Middle: ▫ Contains glands that produce the mucus.

4. Esophagus Outer: ▫ Two layers of muscles.  One is longitudinal, running the length of the tube.  One is circular and passes around the tube.

6. Peristalsis Wavelike muscle contractions that squeeze food along the digestive tract. Only works in one direction, except when we are ill.

8. Cardiac Sphincter At the end of the esophagus. A muscular ring that allows food to go into the stomach. Then squeezes shut to keep food/fluid from going back. ▫ If it does not close fully, it can cause heartburn and acid reflux.

10. Stomach Continues mechanical and enzymatic digestion. Stomach muscles churn and mix the bolus with gastric acid and enzymes. Enzymes include: ▫ Pepsin – breaks down proteins. ▫ Lipase – breaks down fats.

11. Stomach The broken down bolus is now a thick liquid called chyme. Some nutrients (water, salt, sugar) can be absorbed by blood directly through the stomach wall.