Double circulation
Mammals pump blood through two loops. The right side sends blood to the lungs to pick up oxygen. The left side sends oxygen-rich blood to the body. The heart has four chambers to keep the two kinds of blood apart.
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Analogy
Two separate delivery routes with a pump in the middle.
In practice
The left ventricle has the thickest wall because it must push blood around the whole body.
Practice
Flashcards
- Why is the left ventricle thicker than the right?It pumps blood around the whole body, which needs more pressure than the lungs.
Questions people ask
Why do mammals need a double circulation?
Blood passing through the lungs loses pressure. If it then went straight on to the body, flow would be slow. A second pump boosts the pressure again, giving fast delivery of oxygen to tissues. This supports the high energy use of warm-blooded animals.
What does a heartbeat consist of?
A heartbeat has a filling and a pumping part. The atria contract first and push blood into the ventricles. The ventricles then contract, sending blood into the arteries. Valves close behind it, which creates the familiar lub-dub sound and prevents backflow.