Curious about organism without a pulsating heart.

[HappMatt]

I'm here doing some god awful physiology lab report about to write a paragraph on mean arterial blood pressure and was thinking about the pumping mechanism and was tying to think if there was any such organism which has a continuous flow fluid transport system, and if so what's the biggest one. The only thing i could think of would be small single cell organisms that use diffusion as a means of transport. Not sure if there are any organisms that actually have some sort of continuous non pulsating pump system, but thought some bright minds here may know.

 

[mgb_phys]

Don't athropods use diffusion? There are some pretty big crabs/spiders/lobsters

 

[HappMatt]

I just wiki'ed athropods to see what i could find out and it seems to think i mean to say arthropod. If so here is what wiki says about arthropod hearts:

The heart is typically a muscular tube that runs just under the back and for most of the length of the hemocoel. It contracts in ripples that run from rear to front, pushing blood forwards. Elastic ligaments, or small muscles, connect the heart to the body wall and expand sections that are not being squeezed by the heart muscle. Along the heart run a series of paired ostia, non-return valves that allow blood to enter the heart but prevent it from leaving before it reaches the front.

So it appears as though they may be able to sustain a continuous non pulsitile flow although that is not stated.