ostium(redirected from ostium internum)
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n. pl. os·ti·a (-tē-ə)
1. A small opening or orifice, as in a body organ or passage.
2. Any of the small openings or pores in a sponge, through which water is drawn in.
n, pl -tia (-tɪə)
1. (Zoology) any of the pores in sponges through which water enters the body
2. (Zoology) any of the openings in the heart of an arthropod through which blood enters
3. (Biology) any similar opening
[C17: from Latin: door, entrance]
os•ti•um(ˈɒs ti əm)
n., pl. -ti•a (-ti ə)
a small opening or orifice of the body.
[1655–65; < Latin ōstium entrance, river mouth]