ostium

A small opening or orifice, as in a body organ or passage.

Any of the small openings or pores in a sponge, through which water is drawn in.

An opening or entrance; a mouth; an os.

In zoology: In sponges, the opening of an incurrent canal.

An opening; a passage.

A small opening or orifice, as in a body organ or passage.

Any of the small openings or pores in a sponge.