Why do we need atria?

Question

I know exactly what atria do, but don't really see thier point, would a heart consisiting of just two ventricles not work just as well?

Answer 1

The heart need to be separated. Blood returns to the heart into the atria and then is pumped into the ventricles when atria contract. Then venticles contract and blood leaves via the arteries. There are valves preventing the blood from flowing from the ventricles to the atria, that have room for tendons to stop the valves opening backwards (so only having the vein valves wouldnt be as effective).

There are probably heart designs that would function with only one chamber on each side of the heart, it is just that ours was the best designs that we eveolved via natural selection. There is also a lot of junk in DNA that isn't important. We wouln't necesarily NEED atria if the heart was designed differently.

Think of your question this way, you could ask why elephants need trunks, but they obviously dont.

Answer 2

The use of atrial contraction can be demonstrated by atrial fibrillation patients, whose irregular atrial contraction limits its assistance to the ventricle.  These patients have heart failure symptoms often as their initial presentation.

The ventricles are very muscular and tend to function best when they are stretched to a certain limit, which is not possible at normal heart rates or by simple return of blood from veins.  The "atrial kick" stretches the ventricle to its most powerful potential.

In atrial fibrillation patients, they lack this kick and also tend to beat so fast to limit te ventricular stretch even further, causing blood to back up into the lungs and other veins.

Answer 3

Atria are a critical compnent in the pumping mechanism of the heart. They receive the blood from the periphery and with the force that builds up produce the 1st half of the contraction

Answer 4

I guess (being a scientist not a medic) that they act a bit like a supercharger on a Diesel engine: the blood in the atrium is ready to be squeezed into the ventricles, instead of having to be sucked in (as in a naturally-aspirated engine).

Answer 5

well, it's the pump between the 2 that we need. if we just had a ventricle, it would still need to be split into 2 parts to pump between.

Answer 6

Atria are required to fill the ventricles to capacity so that each stronger ventricle contraction is pumping as much blood as possible.  If the atria weren't there and blood was just allowed to dump into the ventricles without a filling mechanism then the heartbeat wouldn't be as efficient.