ARTERIES CAPILLARIES VEINS

ARTERIES

• Your arteries carry blood from your heart out to the rest of your body.

• They have very thick walls which allow them to withstand the immense pressure created as your heart pumps blood forcefully.

CAPILLARIES

• As blood travels outward, the arteries become smaller and smaller until eventually the blood enters into what are known as capillaries.

• Capillaries are so tiny that blood usually can only get through one cell at a time. It is within the capillaries that oxygen is taken in by the cells, and waste, such as carbon dioxide, is released into the blood.

VEINS

• Eventually the capillaries get bigger and bigger, and then the blood enters into veins. As the blood travels back to the heart your veins get larger and larger

TYPES OF BLOOD VESSELS

• ARE ARTERIES AND VEINS DIFFERENT?

• Arteries carry blood from the heart, while veins bring it back. Arteries have thicker walls than veins, to withstand the force of the blood pumping directly out of the heart.

• WHAT ARE CAPILLARIES?

• About 98 percent of blood vessels are microscopically thin vessels, called capillaries, that form a network between arteries and veins. Their walls are only one cell thick, so that chemicals can pass between the blood and the body’s tissues.

• BLOOD• A liquid tissue, blood consists

of trillions of cells suspended in a watery liquid called plasma. Blood is the body’s transportation system, keeping all tissues and organs supplied with the chemicals needed for life and removing waste. Plasma makes up 55 percent of blood, and red cells around 44 percent. White cells account for less than 1 percent of blood.

• WHAT DO RED BLOOD CELLS DO?

• Red blood cells pick up the life-giving gas oxygen in the lungs and release it throughout the body. A single drop of blood contains about five million of these tiny cells. Each cell is packed with the bright red protein hemoglobin, which binds with oxygen and then releases it where it is needed.

• WHY DO WE HAVE WHITE BLOOD CELLS?

• White blood cells destroy germs and damaged tissue. A drop of blood contains about 7,000 cells, and there are many different types. Some patrol the body like soldiers, swallowing germs. Others produce chemicals, called antibodies, that stick to germs and so make them easier to kill.