Your username could be interpreted as analogous to their digestive system.

Purge the booze, keep the snacks. Yeah that's handy.

turtles, because of the jellyfish they eat have very thick eosophagus lining, i assume thier stomaches are equally touch.

Well, our stomachs are not at full acid all the time, only when we eat. I imagine it's pretty similar.

Don't we all?

It only stops solids above a certain size, so a filter is more accurate. Check valves generally stop everything or all of a class of things, the turtle passes all liquid and some solids

Our heart valves are check valves

Strainers and sieves are filters. A filter is a filter. A reverse filter is still a filter. Direction doesn't make a difference because direction is subjective.

It says spines, rather than spine. The esophagus is covered in spines (think like the spines on a porcupine, not a backbone).

Seems like they meant spines to me? As in those little spikey spines pointing backwards down the esophagus?