2007-10-09 15:47:03 · 4 answers · asked by pussycatz 1 in Science & Mathematics ➔ Biology
They are different sizes in order to supply the right amount of blood to the right places in the right way.
2007-10-09 15:50:39 · answer #1 · answered by Lady Geologist 7 · 1⤊ 0⤋
They have different purposes!
Arteries carry blood from the heart - the blood is at a higher pressure so they need to be thicker and stronger so they don't burst. The heart forces blood out hard enough to carry it around the whole body, so arteries need to be able to withstand this.
Capilliaries take blood to the tissues - they need to be narrow so they have a wide surface area, with thin walls, so that the carbon dioxide can get in and the oxygen can get out.
Veins collect blood and take it back to the heart, but the blood is not being forced into them, so they do not need such thick walls as arteries.
2007-10-09 22:55:46 · answer #2 · answered by Anonymous · 0⤊ 0⤋
They all deal with different pressure gradients. arteries are very thick because they hold high pressure by the time it gets to the capillaries it has a much lower pressure which requires a thin wall. by the time its to the veins there is little to no pressure which is the reason why the veins are so thin. The blood gets back to the heart in the venous system by mainly muscle contraction coupled with the valves in the veins...hope this helped..........Dr. Mike
2007-10-10 00:54:09 · answer #3 · answered by Anonymous · 0⤊ 0⤋
If you believe in God and that God did not make some mistakes in the design of the human body then that's nice, but it has no place in the study of science. It just makes it sound stupid, both for God and for the science you are trying to describe.
2007-10-09 23:17:21 · answer #4 · answered by Zelda Hunter 7 · 0⤊ 0⤋