Human Biology

1.23. Heart http://www.ck12.org

FIGURE 1.42

Blood flows in only one direction in the

heart. Blood enters the atria, which con-

tract and push blood into the ventricles.

The atria relax and the ventricles fill with

blood. Finally, the ventricles contract and

push blood around the body.

Summary

• Blood enters the heart at the atria and then flows into the ventricles, which contract and push blood around the
  body.


• Valves in the heart keep the blood flowing in one direction.

Practice

Use the resource below to answer the questions that follow.

• Working of the Heartat http://www.youtube.com/watch?v=NF68qhyfcoM (1:36)

MEDIA

Click image to the left for more content.

1. How many chambers does a mammalian heart have? What are these chambers called?


2. What are the smallest blood vessels in the body? What is there function?


3. What is the function of the circulatory system? What role does the heart play?


4. What passes from the cells into the capillaries? What passes into the cells from the capillaries?

Review

1. Where does oxygen-poor blood first enter the heart?


2. What is the purpose of the valves in the heart?