2007-03-22 03:25:26 · 6 answers · asked by Emily M 1 in Science & Mathematics ➔ Medicine
Because arteries have a constant pumping action that moves blood through them. Veins do not - blood is moved through veins by the movement of muscles around them (like, say, your biceps). The valves are unidirectional, meaning that they only allow blood to go in one direction: towards the heart. Otherwise, blood would pool at the bottoms of your feet.
2007-03-22 03:29:53 · answer #1 · answered by Brian L 7 · 2⤊ 0⤋
Valves in veins prevent blood from pooling in the extremities.
There are no valves in arteries,the flow of blood to the rest of the body is controlled by valves in the heart which maintains your blood pressure.
2007-03-22 10:34:55 · answer #2 · answered by Billy Butthead 7 · 0⤊ 0⤋
Arteries are the vessels going away from the heart. Therefore they contain blood with high pressure due to the pumping action of the heart.
Veins on the other hand are vessels going to the heart containing 'sluggish' blood with low pressure. Sometimes blood in veins has to travel also against gravity eg from the legs to the heart. Therefore valves are needed to prevent backflow ie preventing blood from going in the wrong direction
2007-03-22 10:39:46 · answer #3 · answered by Sephora C 2 · 0⤊ 0⤋
Valves control the flow of blood and provide energy for the blood to keep flowing. Arteries receive so much force from the heart that the blood in them can keep running in one direction. With veins, the blood can actually slow down so much that the blood is in danger of back-flowing, which the valves prevent.
2007-03-22 10:29:58 · answer #4 · answered by J Z 4 · 1⤊ 0⤋
blood flows at very low pressures in the veins,in fact at the point where the inferior vena cava empties into the right atris the diastolic pressure drops to 0mm of mercury. there is therefore a most potent chance of backflow in the greater veins, especially because the peripheral reistance in these vessels also is lower because of the greater diameter (poiseulle's eqn). valvular dysfunction can cause damming of blood in the lower limbs due to gravity causing varicose veins.in the arterise,conversely the pressure of flow is very high, enough to maintain the unilateral flow of blood.
2007-03-22 12:46:56 · answer #5 · answered by rara avis 4 · 0⤊ 0⤋
There are valves in your arteries.
Just take the heart as an example.
2007-03-22 10:29:09 · answer #6 · answered by Anonymous · 0⤊ 1⤋