Heart Structure & Double Circulation

Science · Organisms & Life Processes · ages 12-13

Name ______________________ Date ____________

What is the job of the atria?
- To pump blood out to the lungs and body
- To receive blood entering the heart
- To stop blood flowing backward
Which chamber receives blood coming in from the body through the vena cava?
- Right atrium
- Left atrium
- Right ventricle
The heart has four chambers: two atria and two ventricles.
Circle one: True False
The left ventricle squeezes and pressure inside it rises sharply. What happens to the valve between the left atrium and left ventricle?
- It shuts to stop blood pushing back into the atrium
- It opens wider to let more blood in
- It stays exactly the same
Blood has just left the right ventricle. Where is it heading next?
- To the body
- Back to the right atrium
- To the lungs
Which blood vessel has the thickest, most muscular walls, built to handle high pressure fresh from the heart?
- Vein
- Artery
- Capillary
The valve between the right atrium and right ventricle fails to close properly. What is most likely to happen when the ventricle squeezes?
- Some blood leaks backward into the right atrium
- The left side of the heart beats faster
- The lungs stop receiving any blood at all
A student says: "Blood leaves the left ventricle, travels around the body, then comes straight back into the left atrium." What is wrong with this?
- Blood never actually reaches the body
- The left ventricle does not pump blood out
- Blood returns to the right atrium, not the left atrium

Answer key

For grown-ups. Fold this page away before handing over the rest.

To receive blood entering the heart · Atria are the top chambers. They receive blood before passing it down into the ventricles.
Right atrium · Blood from the body enters through the vena cava into the right atrium, the receiving chamber on that side.
True · Two atria sit on top and two ventricles sit below, one pair on each side of the heart.
It shuts to stop blood pushing back into the atrium · Rising pressure pushes the valve shut, so blood is forced forward into the aorta instead of backward into the atrium.
To the lungs · The right ventricle pumps blood into the pulmonary artery, which carries it to the lungs to pick up oxygen.
Artery · Arteries carry blood away from the heart under high pressure, so they need thick, stretchy, muscular walls.
Some blood leaks backward into the right atrium · A valve that will not shut lets blood push backward into the chamber above instead of only moving forward, which is why leaky valves make the heart pump less effectively.
Blood returns to the right atrium, not the left atrium · After delivering oxygen to the body, blood is low in oxygen again and must return to the right side of the heart to be sent to the lungs, not straight back to the left atrium.