Your Digestive System Objectives Describe the three main functions of the digestive system. Identify the organs of the digestive system and their functions.

Functions of the Digestive System Your digestive system has three main functions digestion absorption elimination

Digestion The process by which the digestive system breaks down food into molecules that the body can use is called digestion. During mechanical digestion, foods are physically broken apart into smaller pieces. During chemical digestion, chemicals produced by your body break large molecules into smaller ones that your body can use. Most of the chemicals involved in digestion are enzymes, substances that speed up reactions.

Absorption and Elimination Absorption is the process by which nutrients pass through the lining of your digestive system into your blood. Materials that are not absorbed are eliminated from the body as wastes.

Structures of the Digestive System The organs of the digestive system include the mouth pharynx esophagus stomach small intestine large intestine liver gallbladder pancreas

Mouth Your teeth tear, crush, and grind your food. Your tongue pushes the food around. An enzyme in saliva begins to break down starches in your food. Saliva moistens the bites of food.

Pharynx 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.

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.

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

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. Chemical digestion occurs as cells lining the stomach release gastric juice. Peristalsis moves the food, which is now a thick liquid called chyme (kym), into the small intestine.

Small Intestine The small intestine is where most chemical digestion and absorption of nutrients takes place. Liver The 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 (singular, villus).

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.

Vocabulary digestion The process by which the digestive system breaks down food into molecules that the body can use. enzyme A chemical that speeds up reactions in the body. absorption The process by which nutrients pass through the lining of the digestive system. pharynx The upper portion of the throat; the junction between the digestive and respiratory systems. epiglottis A flap of tissue that seals off the trachea when food or liquid is swallowed. peristalsis Waves of muscle contractions that push food through the digestive system.

Vocabulary chyme A thick mixture of food and gastric juices formed in the stomach. bile A substance produced by the liver that aids in digestion by breaking up large fat droplets. gallbladder The organ that stores bile and releases it into the small intestine. villi Tiny fingerlike projections lining the small intestine, through which nutrients are absorbed into the blood.