The heart is simply a pump, which circulates blood throughout the body. Tubes called blood vessels carry it from the heart to all parts of the body and again. this round trip is known as the circulation .

Екатерина в категроии Английский язык, вопрос открыт 06.02.2018 в 19:56

vessels carrying blood away from the heart are known as arteries and those returning blood to the heart are known veins