Click on a Key Concept to link to the page where the concept is explained.

 Key Concepts   

• 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.

Vocabulary

 Key Concepts   

• Red blood cells transport oxygen.
• White blood cells guard against infection, fight parasites, and attack bacteria.
• Blood clotting is made possible by plasma proteins and cell fragments called platelets.

• A network of vessels, nodes, and organs called the lymphatic system collects the fluid that is lost by the blood and returns it to the circulatory system.

Vocabulary

 Key Concepts   

• The basic function of the human respiratory system is to bring about the exchange of oxygen and carbon dioxide between the blood, the air, and tissues.

• Smoking can cause such respiratory diseases as chronic bronchitis, emphysema, and lung cancer.

Vocabulary

Circulatory System