The circulatory system has the following components:

• the blood - a complex fluid containing specialised cells suspended in liquid plasma
• the heart - a double pump that pumps blood into the blood vessels, and
• the blood vessels.

The blood vessels comprise:

• the arteries, which carry blood from the heart to the tissues
• the veins which bring blood back from the tissues to the heart, and
• the capillaries – tiny vessels found throughout
• the tissues that link the arteries and veins.