Biology for IGCSE & O level - Transport In Animals (Section 3 - No. 18)

In the mammalian circulatory system, the blood flows through the heart _______.

once during a complete circulation

twice during a complete circulation

three times during a complete circulation

four times during a complete circulation

Mammalian blood passes through the heart twice in a complete circuit: once to the lungs and once to the rest of the body.