Circulatory system

Science

Definition

The circulatory system transports blood throughout the body, delivering oxygen and nutrients to cells while removing carbon dioxide and waste products. In humans, it consists of the heart, blood vessels (arteries, veins, capillaries), and blood.

Examples

  • The heart pumps about 2,000 gallons of blood per day through roughly 60,000 miles of blood vessels
  • Red blood cells use hemoglobin to carry oxygen from the lungs to body tissues
  • White blood cells circulating in the blood help defend against infections

Related Terms

Digestive system Immune system Nervous system Cell transport

Study This Concept

Practice circulatory system with free review games in these units:

Biology Unit 8: Human Body Systems