The links at left lead to additional resources to help you learn about the topics in this chapter. These resources include Hot Links to Web sites related to the subject of these topics, the Take It to the Net activities referred to in your textbook, and a Self-Test you can use to test your knowledge of this chapter.
Science News topics pages correlate recently published articles to the topics you are studying.
Section 37-1: The Circulatory System
The human circulatory system consists of the heart, a series of blood vessels, and the blood that flows through them.
As the blood flows through the circulatory system, it moves through three types of blood vessels—arteries, capillaries, and veins.
Section 37-2: Blood and the Lymphatic System
Red blood cells transport oxygen.
White blood cells attack foreign substances or organisms.
Blood clotting is made possible by plasma proteins and cell fragments called platelets.
A network of vessels called the lymphatic system collects the fluid that is lost by the blood and returns it to the circulatory system.
Section 37-3: The Respiratory System
The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, and lungs.
Smoking can cause such respiratory diseases as chronic bronchitis, emphysema, and lung cancer.