Fenestra

A fenestra (plural fenestrae) in anatomy, zoology and biology, is any small opening or pore. It is Latin for window and is used in various fields to describe a window, or opening in a structure.

In gross anatomy in zoology fenestrae are often found in bones particularly in the skull. In anatomy the round window and oval window are also known as the fenestra rotunda and the fenestra ovalis.

In microanatomy they are found in endothelium and fenestrated capillaries and allow for the rapid exchange of molecules between the capillaries, sinusoid blood vessels and surrounding tissue. These pores may enlarge and contract in response to various stimuli such as the hormone noradrenaline. The elastic layer of the tunica intima is a fenestrated membrane.

In surgery a fenestra is a new opening made in a part of the body to enable drainage or access.

In biology the perforations in a perforate leaf are also described as fenestrae and the leaf also called a fenestrate leaf. The leaf window is also known as a fenestra, and is a translucent structure that transmits light, as in Fenestraria.

In zoology the trilobite Fenestraspis possessed extensive fenestrae in the posterior part of the body and apparently the thorax. In the paleognathae there is an ilio–ischiatic fenestra.

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