Boxi Learn › Biology › Stage 3 · Structure and Evidence
The heart is two pumps
BIO-2 Structure fits functionX-3 Look from another side
What many people think
Blood without oxygen is blue; that is why veins look blue.
The idea
Blood goes through the heart twice per lap: the right side pumps it to the lungs, the left side pumps it to the body; it is always red, bright when full of oxygen and dark when not.
Explain it
A friend says blood in your veins is blue until it touches air. Explain why that is wrong, and why the pulmonary artery carries dark red blood even though it is an artery.
Try at home
Find the pulse on your wrist; count the beats for 15 s and multiply by 4. Do 30 jumping jacks and count again. Taking about 70 mL per beat, how many litres a minute did your heart pump each time?