All animals need to transport materials around to the different parts of their body. This is the job of the circulatory system. The circulatory system consists of a liquid called (1) ________, a pump called the (2) ________ and a series of vessels called (3) ________ and (4) ________.
One thing that must be transported around is a gas called (5) ________. Oxygen enters the blood through the lungs. It is then pumped through the heart and around the body where it is used along with food to make energy. The body produces another gas called (6) ________, which is a waste product. This gas is carried back to the heart and then to the lungs where it is released back into the (7) ________.
The vessels that transport blood away from the heart are called arteries. The blood in arteries is (8) ________ red because it is rich in oxygen. The vessels that transport blood to the heart are called veins. The blood in veins is (9) ________ red because it is low in oxygen. (10) ________ are small vessels that join the arteries and veins.
(11) ________ from food are also transported around the body by the circulatory system. They enter the blood from the small (12) ________. The circulatory system also helps to regulate temperature by transporting heat around the body.