"Which layer of blood vessels has a high number of openings that allow for the movement of solutes?"

it is called the mitotic spindle

fumikage isn't really a bird, and tsuyu does have teeth. tsuyu has a transformation quirk which still allows her to be partially human. otherwise we'd have a large frog running around. fumikage has teeth because again, he isn't a bird. his head was a quirk mixture if i'm correct.