2006-12-02 11:32:31 · 6 answers · asked by Ariana 2 in Science & Mathematics ➔ Biology
Because of your lungs. And your kidneys. And a bunch of other organs.
OK - to be more specific, your blood flows around as a transportation device for many things, including oxygen delivery, refuse pickup (waste products, carbon dioxide).
The unidirectional flow of blood allows your organs to work such that items (oxygen, CO2, waste products, etc) can move in one direction also. You want oxygen to move in one direction (into your blood @ the lungs, into your cells), you want CO2 to move in one direction (into your blood @ the cells, into your lungs and out). You want waste products to move in one direction (into your blood, then into your kidneys for disposal).
If this didn't occur in one direction, it would require a much more complex system for your organs to know when to pick up / drop off items from your blood. Imagine if your lungs removed oxygen from your blood!
2006-12-02 11:34:45 · answer #1 · answered by sep_n 3 · 0⤊ 0⤋
1) The heart when normally functioning will pump blood only in one direction. Yes, there are four chambers, but it is timed so that the first set (atria) pumps before the second set (ventricles), and because of this the blood will flow in that direction with at least 110mmHg (pressure) in a healthy adult.
2) A majority of your veins have one way valves in them. This prevents the reverse of blood flow and gravity from pulling blood downwards and keeping it in your feet.
3) Even if you surgically reversed the blood inputs/outputs to the heart (putting the vena cava at the left ventricle and aorta at the right atrium), you cannot reverse flow. The veins are not designed like arteries; veins can expand while arteries constrict. So reversing blood flow will only expand the veins since any blood pressure in the arteries would just push blood back into the veins. This is what happens when you are dead, your veins hold most of the blood since the arteries squeeze it into there.
4) Because of #3, blood will be fighting for space against itself in the venous half of the circulatory system and eventually balloon and burst. Also none of your organs would be able to function properrly since blood cannot leave the organs.
2006-12-03 00:12:44 · answer #2 · answered by Carl D 4 · 1⤊ 0⤋
Blood Pressure. Stop the pressure and the blood will be able to flow in both directions, but you would be dead at that point.
2006-12-02 19:41:15 · answer #3 · answered by Pundit Bandit 5 · 0⤊ 0⤋
The short answer is that the blood vessels have valves inside them much like the heart valves that prevent back flow of blood. For the long answer see the guy who answered before me.
2006-12-03 12:21:01 · answer #4 · answered by LYN 2 · 0⤊ 0⤋
Well, theoretically, I suppose it could, but the system is not designed for it. It would be sort of like having sewage flow up out of your sink drain and proceed to flow into your clean water pipes. It might be possible (but unlikely), and anyway, what would be the point?
2006-12-02 20:56:11 · answer #5 · answered by Sciencenut 7 · 0⤊ 0⤋
simple answer! your heart is a one-way pump and there are no vessels that cross from high pressure (arteries) to low pressure (veins) directly. your cirulatory system is a loop. if it weren't your blood wouldn't circulate it would all puddle in your feet and none would be in your head. if there were cross over vessels instead of pumping your blood around the pressure would be equal and you would look like a balloon being squashed every time your heart beat.
2006-12-02 21:57:43 · answer #6 · answered by P W 5 · 0⤊ 0⤋