Blood vessels- capillaries

As blood passes from an artery to a vein it travels through very small blood vessels called capillaries. All arteries carry blood from the heart to this fine network of capillaries. Capillaries empty into small veins where the blood is transported back to the heart.

Consider the animation on the left. The yellow dot indicates the path the blood travels.



As blood passes from an artery to a vein it travels though very small blood vessels called capillaries. Capillaries are only 5 -10 microns in diameter. The walls of these tiny blood vessels are very thin and are composed of overlapping endothelial cells which allow nutrients and waste to pass through. Red blood cells can squeeze through the capillaries one at a time, as shown on the left.

White blood cells can freely pass through the walls of a capillary.
Red blood cells travel in single file through the capillaries. These tiny blood vessels finally empty into larger blood vessels, called veins, that take blood back to the heart. The sole function of red blood cells is to transport oxygen to different parts of the body. Red blood cells contain a special carrier protein called hemoglobin. This molecule binds oxygen and carries it to the parts of the body where it is needed.
1) Which of the following best describes the passage of blood from the heart, through the network of blood vessels?
2) What can pass through the walls of capillaries?
3) Which comment is true?
4) Capillaries have
5) Oxygen and nutrients pass out of
6) High blood pressure is dangerous because it is likely to damage delicate blood vessels such as
7) Diffusion of solutes between the blood and the extracellular fluid occours in the
8) High blood pressure will most likely increase