The Digestive System

1. The Digestive System Your digestive system has three main functions • digestion • absorption • elimination

2. Mouth Mastication: teeth tear, crush, and grind your food. An enzyme in saliva begins to break down starches in your food. The pharynx is the junction between the digestive tract and the respiratory system. A flap of tissue called the epiglottis seals off the trachea, or windpipe, preventing food and liquid from entering your lungs.

3. Esophagus • After passing through the pharynx, the food enters the esophagus, a muscular tube that connects the pharynx to the stomach • Waves of muscle contractions, called peristalsis, push food through the rest of the digestive system.

4. Pharynx Mouth Epiglottis Salivary gland Esophagus Liver Stomach Pancreas Small intestine Large intestine Gallbladder Rectum

5. Stomach • From the esophagus, food passes through a valve and into the stomach, a muscular pouch located in the abdomen. • Mechanical digestion occurs as three layers of muscle produce a churning motion. • Pepsin: breaks down the proteins • Hydrochloric acid: kills bacteria • Peristalsis moves the food, which is now a thick liquid called chyme (kym), into the small intestine.

6. Small Intestine • The small intestine is where most chemical digestion and absorption of nutrients takes place. It’s about 22 feet long. • LiverThe role of the liver is to produce bile. Bile is a substance that physically breaks up large fat droplets that clump together. • Gallbladder Bile flows from the liver into the gallbladder, the organ that stores bile. • Pancreas The pancreas secretes enzymes into the small intestine that complete the breakdown of carbohydrates, proteins, and fats. • The lining of the small intestine is covered with millions of tiny fingerlike projections called villi.

7. The Large Intestine • The large intestine is about 5 feet long and 3 inches wide. • As the material moves through the large intestine, most of the remaining water is absorbed into the blood. • Collects waste from the small intestine and gets rid of it

8. Rectum A short, muscular tube that forms the lowest portion of the large intestine and connects it to the anus. Feces collects here until pressure on the rectal walls cause nerve impulses which send messages to the voluntary muscles in the anus to relax, permitting expulsion.

11. Avoiding Digestive Disorders • Healthy eating habits and regular exercise are important for keeping your digestive system healthy. • Consume plenty of fiber. • Avoid fatty foods. • Eat moderately. • Plan meals for a time when you can relax. • Drink water. • Get regular exercise.