The uterus keeps the trachea from collapsing in a fetal pig.
Its cytoplasm.
cytoplasm
The sphere of the eye has the lowest internal stress energy of geometric structure and even if a vitrectomy has been performed removing all the fluid the eye maintains most of it's original shape
hydrostatic
Dynamic equilibrium.
gravity maybe?
The trachea has a series of cartilage rings that prevent it from collapsing.
It keeps the eye in place and protects it.
Yes, the space it occupies keeps the ball from collapsing in on itself and going flat.
it surrounds you eye muscles
1) Surfactant keeps it from collapsing completely, but 2) Air pressure inflates it beyond the minimum (the lower pressure around it is developed by the chest wall & the diaphragm.)