Chapter 8 Lesson 4 "How the Body Gets Rid of Wastes"

Materials:

• A little water for students to dab on their wrists.
• Notes for Lesson 4, Use this worksheet if you like.
• Excretory System Worksheet.

Objective:

• 1. After this lesson students will be able to explain how perspiration gets rid of wastes.
• 2. After this lesson students will be able to describe the function of kidneys.
• 3. After this lesson students will be able to explain how urine leaves the body.

Alaska Content Standards:

• SCI A-10 Students will understand that living things are made up mostly of cells and that all life processes occur in Cells (Cells)
• SCI A-12 Students will distinguish the patterns of similarity and differences in the living world in order to understand the diversity of life and understand the theories that describe the importance of diversity for species and ecosystems.

Anticipatory Set: Have the students pull up their sleeves and blow on their wrists. Have them describe the way it feels. Then, have the student dampen their wrists with a small bit of water. Ask them again how it feels. It should feel much cooler with the water than without. The same thing happens with perspiration. Perspiration is one way the body cools itself.

Teacher Input: Have the students take out their notes and go through the three objectives of this section. As the lesson is covered students will create a statement that demonstrates that they have learned that objective.

Students will start with a discussion of the skin. Find out how much the students know with these questions: How many layers does the skin have? What types of things do you find in the skin? What are part of the skin secretes something to cool the body? What does it secrete? Show this picture of the skin or P184, and go through the answers to the above questions in detail. Then show the "skin" part of the ADAM CD, skin components, sweating, sun's effect on skin, skin conditions.

Now start a discussion about how your body gets rid of poisonous substances in the body. As your digests and uses food for energy the cells in your body create a nitrogen waste. How does your body get rid of that waste? What organs are used? What is the main organ for getting rid of Nitrogen waste? What other organ does this remind you of from the last lesson that removes a harmful substance from the blood? What are three things commonly removed by the kidneys? Where does the nitrogen waste go after it is collected out of the blood by the kidneys? Show a picture of the Excretory System P185 and answer these questions in great detail. Show the urinary system on the ADAM CD, mention that the urinary system and the excretory system are the same thing.

Check for Understanding: Go through the question on P186 with the students help them with ideas that are difficult for them.

Closure: Sum up the ideas of this lesson for the students: Kidneys filter blood to eliminate nitrogen wastes from the breakdown of proteins and nucleic acids. Most of these nitrogen wastes are excreted as urea. Kidneys also help regulate blood pressure by balancing the amounts of water and salt in the body. Each kidney has about one million filtering units called neurons. Besides producing perspiration that evaporates and cools the body, the skin contains blood vessels that also help regulate body temperature. These blood vessels constrict to prevent heat loss when the temperature is cold. they dilate (enlarge) to release heat when a person becomes hot.

Independent Practice: Have the students complete the worksheet on excretion. Students will take the quiz on Lesson 4.

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).