An ostium (pl.: ostia) in anatomy is a small opening or orifice.

Ostium or ostia may refer to:

Human anatomy[edit]

• Ostium of fallopian tube
• Ostium of the uterus (disambiguation)
• Ostium primum of the developing heart
• Ostium secundum (foramen ovale) of the developing heart
• Ostium maxillare of the maxillary sinus
• Ostium vaginae (vaginal orifice)
• Coronary ostium – opening of coronary arteries at root of aorta, superior to aortic valve
• Sinus ostium an opening that connects a sinus to the nasal cavity itself.

In other animals[edit]

• Ostium (sponges), the pores of living sponges
• Ostia of female lepidoptera genitalia

See also[edit]

• All pages with titles containing Ostium
• Pore (disambiguation)
• Foramen
• Ostiole