1. Organs and Organ Systems
- Body Organization and Homeostasis
Organs and Organ Systems
Each organ in your body is part of an organ system, which is a group of organs that work together to perform a major function.

2. What the Skeletal System Does
Your skeleton has five major functions. It provides shape and support, enables you to move, protects your organs, produces blood cells, and stores minerals and other materials until your body needs them.

3. Joints of the Skeleton - The Skeletal System
A joint is a place in the body where two bones come together. Joints allow bones to move in different ways.

4. Bones—Strong and Living
- The Skeletal System
Bones—Strong and Living
Bones are complex living structures that undergo growth and development.

5. Asking Questions - The Skeletal System
Before you read, preview the red headings. In a graphic organizer like the one below, ask a what or how question for each heading. As you read, write answers to your questions.
Question
Answer
What does the skeleton do?
The skeleton provides shape and support, helps you to move, protects organs, produces blood cells, and stores minerals and other materials.
How do joints move?
Joints can move forward or backward, in a circle, in a rotating motion, and in a gliding motion.
How strong are bones?
Bones can absorb more force without breaking than granite or concrete.
What can I do to care for my bones?
Eat a well balanced diet and get
plenty of exercise.

6. Muscles at Work - The Muscular System
Because muscle cells can only contract, not extend, skeletal muscles must work in pairs. While one muscle contracts, the other muscle in the pair relaxes to its original length.

7. Previewing Visuals - The Muscular System
When you preview, you look ahead at the material to be read. Preview Figure 15. Then, in a graphic organizer like the one below, write three questions that you have about the diagram. As you read, answer your questions.
Types of Muscle
Q. How does skeletal muscle help my body move?
A. Skeletal muscles are attached to the ends of bones and provide the force to move them.
Q. Where is smooth muscle found?
A. The inside of many internal organs
Q. Why is cardiac muscle considered a special type?
A. It is found only in the heart; it is like smooth muscle because it is involuntary and like skeletal muscle because it is striated.

8. Click the Video button to watch a movie about skeletal muscles.
- The Muscular System
Skeletal Muscles
Click the Video button to watch a movie about skeletal muscles.

9. Click the PHSchool.com button for an activity about muscle types.
- The Muscular System
More on Muscle Types
Click the PHSchool.com button for an activity about muscle types.

10. The Epidermis - The Skin
The skin is organized into two main layers: the epidermis and the dermis.

11. Identifying Main Ideas
- The Skin
Identifying Main Ideas
As you read the section titled “The Body’s Tough Covering,” write the main idea—the biggest or most important idea—in a graphic organizer like the one below. Then write five supporting details. The supporting details give examples of the main idea.
Main Idea
The skin has several important functions.
Detail
Detail
Detail
Detail
Detail
The skin forms a barrier against disease-causing microorganisms and loss of fluids.
The skin helps the body maintain a steady temperature.
The skin helps to eliminate wastes through perspiration.
The skin contains nerves that gather information about the environment.
Skin cells produce vitamin D that helps your body absorb calcium.

12. Graphic Organizer Muscles Involuntary muscles Voluntary muscles
can be
Involuntary muscles
Voluntary muscles
include
include
Smooth muscles
Cardiac muscles
Skeletal muscles