Fenestrae

Fenestrae (singular: fenestra) are small pores in epithelial cells to allow for rapid exchange of molecules between blood vessels and surrounding tissue. These pores can enlarge and contract at the action of various stimuli such as noradrenaline.

In anatomy, the term is used to refer to natural (as opposed to traumatic) openings in the skull or other bones. Fenestrae is the Latin plural for windows.