Circulatory
System
The circulatory
system is the body's transport system. It is made up of a group of organs that
transport blood throughout the body. The heart pumps the blood and the arteries and veins transport
it. Oxygen-rich blood leaves the left side of the heart and enters the biggest
artery, called the aorta. The aorta branches into smaller arteries
which then branch into even smaller vessels that travel all over the body. When
blood enters the smallest blood vessels, which are called capillaries,
and are found in body tissue, it gives nutrients and oxygen to the cells and
takes in carbon dioxide, water, and waste. The blood, which no longer contains
oxygen and nutrients, then goes back to the heart through veins. Veins carry
waste products away from cells and bring blood back to the heart , which pumps
it to the lungs to pick up oxygen and eliminate waste carbon dioxide.