The Digestive and Excretory Systems In this lesson

The Digestive and Excretory Systems In this lesson, you will Learn About… n How your body digests food. n How your body removes waste products.

The Digestive and Excretory Systems The Vocabulary terms in this lesson are: n Digestion. n Pancreas. n Digestive system. n Excretion. n Saliva. n Excretory system. n Small intestine. n Colon. n Liver. n Kidneys.

Turning Food into Fuel When you eat, your body’s digestive system breaks the food down into smaller parts so it can use the nutrients in the food for fuel. This is the process of digestion. Mouth Crushing and Grinding Stomach Small Intestine Useful Chemical Material Breakdown Extracted Colon Water Removal Waste Elimination

How Digestion Begins Saliva is a digestive juice produced by the salivary glands in your mouth. It starts to flow as a physical signal from your body that it is ready to begin the digestive process. When you chew your food and swallow it, your body initiates the digestive process.

Chewing and Swallowing teeth tear and grind the 1 The food into small shreds or chunks. 2 The salivary glands produce saliva. Enzymes in saliva begin the chemical breakdown of carbohydrates. Moistens and softens food for its transport 3 When you swallow, a flap of the food is 4 Once swallowed, it enters the esophagus. Pushes the food along until it reaches the stomach. skin called the epiglottis closes off the trachea to keep food from entering it. At the same time, the uvula closes off the airway to the nose.

Organs of the Digestive System 1 Acid and enzymes in the stomach break down food until it resembles a thin soup called chyme. 2 Next the food moves to the small intestine. Most of digestion takes place here. 3 The liver secretes bile to help digest fats. 4 After the liver produces bile, it sends it to the gallbladder. 5 The pancreas produces pancreatic juice to break down proteins, carbohydrates, and fats. Nutrients from the 6 digested material pass through the small intestine. Villi, bloodstream, body cells.

Removing Wastes from the Body Some foods that you eat contain substances that the body cannot use. During the digestive process, these wastes are separated out. The wastes are removed from the body through a process called excretion. The major organs of the excretory system are the kidneys, bladder, and colon.

Eliminating Liquid Wastes 1 The kidneys filter water and waste materials from the blood. 2 The kidneys send the urine to the bladder through two tubes called ureters. 3 The urine is stored in the bladder. 4 Urine passes out of the body through a tube called the urethra.

Solid Wastes Solid wastes are made up of foods that your body cannot break down, including fiber. After digestion, the body sends a mixture of water and undigested solid wastes into the colon. Most of the water is absorbed by the colon and returned to the body. The remaining solid wastes become material called feces.

Caring for Your Digestive and Excretory Systems To keep the digestive and excretory systems working well: n Eat a balanced diet that is based on the Food Guide Pyramid. n Eat plenty of foods that are low in fat and high in fiber. n Eat at regular times each day. n Drink eight to ten glasses of water every day. n Take care of your teeth. n Stay active.

Reviewing Terms and Facts 1. Define the term digestion. Digestion is the process by which the body breaks down food into smaller components that can be absorbed by the bloodstream and sent to each cell in the body.

Reviewing Terms and Facts 2. Identify the major organs of the excretory system. n Kidneys n Bladder n Colon

Thinking Critically 3. Describe possible consequences for the rest of the body if the digestive system is not working properly.

Vocabulary Review Digestion is the process by which the body breaks down food into smaller components that can be absorbed by the bloodstream and sent to each cell in the body.

Vocabulary Review The digestive system is a group of organs that work together to break down foods into substances that the cells can use.

Vocabulary Review Saliva is a digestive juice produced by the salivary glands in the mouth.

Vocabulary Review The small intestine is a coiled tube, about 20 feet long, where most of the digestive process takes place.

Vocabulary Review The liver, the body’s largest gland, secretes a liquid called bile that helps to digest fats.

Vocabulary Review The pancreas is a gland that helps the small intestine by producing pancreatic juice, a blend of enzymes that breaks down proteins, carbohydrates, and fats.

Vocabulary Review Excretion is the process by which the body gets rid of waste materials.

Vocabulary Review The excretory system is the system that removes wastes from the body and controls water balance.

Vocabulary Review The colon is a storage tube for solid wastes.

Vocabulary Review The kidneys are a pair of organs that filter water and waste materials from the blood.