Assertion: epithelium's surface | /r/HasProperty | exposed to external environment
Facets:
Source sentences:
text: The apical surface of these epithelial cells is exposed to the "external environment", the lumen of the organ or the air.
text: They have 1 surface that is not attached to any cell, either exposed to the external environment or the lumen of an organ.
text: The apical surface of this membrane is exposed to the external environment and is covered with dead, keratinized cells that help protect the body from desiccation and pathogens.