Fenestra

This article is about the biological term. For the software company, see Fenestrae B.V..

Scanning electron micrograph of a liver sinusoid with fenestrated endothelial cells. Fenestræ are approx 100 nm in diameter, with a sinusoidal width of 5 micrometres. Magnification 30,000X

Fenestræ (singular: fenestra) is a Latin word that means "window".

• In histology, fenestræ are small pores in endothelial cells that allow for rapid exchange of molecules between sinusoid blood vessels and surrounding tissue. These pores may 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.

See also

• Temporal fenestra
• Sinusoid (blood vessel)
• Liver sinusoid