The job of the circulatory system is to circulate, or constantly move, blood around the body. Blood carries oxygen and nutrients to cells. It also collects cellular waste like carbon dioxide so that it can be removed from the body.
The circulatory system is composed of the heart, arteries, veins, capillaries and the blood transported by these tissues. Arteries, veins and capillaries are types of blood vessels. Arteries are usually represented in red on a diagram of the circulatory system because they carry oxygen-rich blood. Veins are usually represented in blue because they carry oxygen-poor blood. Capillaries are the smallest blood vessels. They are thinner than a strand of hair. If you straightened out all the blood vessels in the body, the circulatory system’s network would be 60,000 miles long.
Which of these is true of blood?
A
Blood is transported through veins only.
B
Blood brings oxygen and nutrients to cells.
C
Blood carries carbon dioxide to cells for energy.
D
Blood collects capillaries from cells around the body.