What documents do I need to present to reenter the United States? If seeking to enter the United States after temporary travel abroad, you will need to present a valid, unexpired âgreen cardâ (Form I-551, Permanent Resident Card).
Brain Tour. 2. Supply lines. Your brain is nourished by one of your body's richest networks of blood vessels. With each heartbeat, arteries carry about 20 to 25 percent of your blood to your brain, where billions of cells use about 20 percent of the oxygen and fuel your blood carries. When you are thinking hard, your brain may use up to 50 percent of the fuel and oxygen.
There are three main types of blood vessels: 1  arteries take blood away from the heart to the body organs and tissues. 2  capillaries are tiny, thin-walled vessels which form a network to take blood through the organsand tissues. 3  veins collect blood from the capillaries in the body and return the blood to the heart.rteries, veins and capillaries. There are three main types of blood vessels: 1  arteries take blood away from the heart to the body organs and tissues. 2  The artery wall is thick and muscular so it can withstand the high pressure of the blood being pumped directly from the heart.