Earth 2092 intro
Each lung connects to its own air sac to pump air through the lung. the air sacs are filled with a synthetic spongy open cell material to inflate them after the muscles that wrap around them deflate them.
Year 2092
This may have simply been cheap and lazy engineering just like the sponge used to expand their air sacs.
Goop to the Last Drop
The stallion's hooves scooted forward, pushing against her swollen sac, eliciting a gurgling rumble from the mare as she closed her eyes and shuddered.
No Longer a Liability (A SynTech Story)
One side of his plump sac pressed outwards, butting into the belly of one otter, whose blush, aroused bulge, and failure to move away spoke volumes.
Punching Bag...
Marco slid a small door open, letting drax's huge ball sac drop down. slowly the old roo slid the door closed trapping the neck of drax's low dangling ball sac. once he'd got it all in place, and the platform was at the right height.
James, Cougar
Making the decision, he pressed the three claws against his sac, and with a loud growl, swiped.
The Triple Milker, Part 4
The creature slowly retracted into the ceiling, its sac now almost completely full of cum.
Hotel Peeks - Cow Udder Vore
You were waist deep in the fleshy sac at this point, and that was quickly changing...your head bumped into the back of the chamber, and you started to have to curl up inside the udder, the stretchy sac accompanying your whole body quite easily as your legs
Fusion
Then it moves all the way to dazins tail as he spreads it across it as he lays limp on kyle's sac. his sacs begin to swell up to the hight of the bed to the floor up. the goo created a webbing under dazins tail as it slowly begins to sink into the sacs.
Invasion of the Tentacle Monsters Chapter 3
The horse cock wrapped around the sac and moved it to the corner of the room. slime pooled around the shape began to thicken. the horse cock moved the protective covering to set the sac upright. pulsing shapes began to well beneath its surface.
Bill's Big Cock
The other two foxes watched as their comrade's detailed bulge slid down and disappeared into the sac, only to press out of the sacflesh. the cock bent down, as if looking at the other two foxes.
Turn of Event's
His thrusting, his own sac being slapped by abine's.