Antrum

In biology, antrum is a general term for a cavity or chamber which may have specific meaning in reference to certain organs or sites in the body.

In vertebrates, it may mean for example:

• antrum cardiacum, a dilation that occurs in the esophagus near the stomach (forestomach)
• antrum follicularum, the cavity in the epithelium that envelops the oocyte
• mastoid antrum, a cavity between the middle ear and temporal bone in the skull
• pyloric antrum, the initial portion of the pyloric part of the stomach. This is what usually is referred to in terms of "antrum" in stomach related topics.
• maxillary antrum or Antrum of Highmore, the maxillary sinus, a cavity in the maxilla and the largest of the paranasal sinuses

In invertebrates, it may mean for example:

• antrum of female lepidoptera genitalia