The Digestive and Excretory Systems

In this lesson, you will Learn About…

How your body digests food.

How your body removes waste products.

The Digestive and Excretory Systems

Digestion.

Digestive system.

Saliva.

Small intestine.

Liver.

The Vocabulary terms in this lesson are:

Pancreas.

Excretion.

Excretory system.

Colon.

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 Chemical

Breakdown

Small Intestine

Useful Material

Extracted

ColonWater

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

The teeth tear and grind the food into small shreds or chunks.

1

The salivary glands produce saliva. Enzymes in saliva begin the chemical breakdown of carbohydrates.

2

When you swallow, a flap of 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.

3

Once the food is swallowed, it enters the esophagus.

4

Organs of the Digestive System

Acid and enzymes in the stomach break down food until it resembles a thin soup called chyme.

1

Next the food moves to the small intestine.

2

The liver secretes bile to help digest fats.

3

After the liver produces bile, it sends it to the gallbladder.

4

The pancreas produces pancreatic juice to break down proteins, carbohydrates, and fats.

5

Nutrients from the digested material pass through the small intestine.

6

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

The kidneys filter water and waste materials from the blood.

1

The kidneys send the urine to the bladder through two tubes called ureters.

2

The urine is stored in the bladder.

3

Urine passes out of the body through a tube called the urethra.

4

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:

Eat a balanced diet that is based on the Food Guide Pyramid.

Eat plenty of foods that are low in fat and high in fiber.

Eat at regular times each day. Drink eight to ten glasses of water every day. Take care of your teeth. 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.

Kidneys Bladder Colon

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

Thinking Critically

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.