What is the function of the valves within the heart and veins? to ensure the production of blood within the body. to ensure coordination of the heart cells for pumping blood. to ensure that foreign materials do not enter the heart. to ensure that blood flows in one direction only.

On edge.nuity the answer should be the last one, D. Hope this helps :)

no, because those are both different running competitions. while distance runners train their legs and their lungs to run long amounts of time, the sprinters are training their legs and their lungs to give all they have in the little amount of area they need to cover. the brain also plays a huge part in all of this.

the brain is the only thing in your body that sends messages to your body telling you to run. if you are a long distance runner and you have the mind set of a sprinter, you will not get anywhere. if you have a long distance mind set and you have to run 200m in 20 seconds then you will not make it in time.