bild

Blood system. Artwork of the blood circulation system on a human figure. The heart (upper centre) is a hollow muscle that pumps blood around the body. At the top of the heart are its main blood vessels. The veins mainly carry deoxygenated blood (blue) towards the heart, while the arteries carry oxygenated blood (red) away from the heart. The fine capillary network (magnified at upper right) transports oxygen and nutrients into the tissues. It links the small artery (arteriole, red) to the small vein (venule, blue). The lungs (upper centre), liver (centre), kidneys (centre) and large intestine (lower centre) are seen. (KEYSTONE/SCIENCE PHOTO LIBRARY/LEONARD E. MORGAN, CUSTOM MEDICAL STOCK PHOTO)