Afenestra (fenestration;pl.:fenestrae orfenestrations) is any small opening or pore, commonly used as a term in thebiological sciences.[1] It is theLatin word for "window", and is used in various fields to describe a pore in ananatomical structure.
Inmorphology, fenestrae are found incancellous bones, particularly in theskull.[2] Inanatomy, theround window andoval window are also known as thefenestra rotunda and thefenestra ovalis.[3] Inmicroanatomy, fenestrae are found inendothelium offenestrated capillaries, enabling the rapid exchange ofmolecules between the blood and surroundingtissue.[4] Theelastic layer of thetunica intima is a fenestrated membrane. Insurgery, a fenestration is a new opening made in a part of the body to enable drainage or access.
Inplant biology, the perforations in aperforate leaf are also described as fenestrae, and the leaf is called a fenestrate leaf. Theleaf window is also known as a fenestra,[5] and is a translucent structure that transmits light, as inFenestraria.
Examples of fenestrate structures in the fungal kingdom include the symmetrically arranged gaps in the indusium ("skirt") of the mushroomPhallus duplicatus,[6] and thethallus of the coral lichenPulchrocladia retipora.[7]
Inzoology, the trilobiteFenestraspis possessed extensive fenestrae in the posterior part of the body.[8] In thePaleognathae, there is an ilio–ischiatic fenestra.
Fenestrae are also used to distinguish the three types ofamniote:
The ancestor of the amniotes is a primitive lizard,Hylonomus. From this reptile, three groups of amniotes would evolve: anapsids, diapsids, and synapsids. These broad groupings of amniotes are most easily differentiated by the presence and number of holes in the skull behind the eye socket. Those gaps, or holes, are called fenestrae, meaning "windows." The anapsids are the most primitive members of the group. They have a complete skull, with no gaps. ... The diapsids [including lizards, dinosaurs, and birds] have two fenestrae in their skulls, one directly behind the eye socket and one just slightly above. [160] The synapsids [including mammals] have just one fenestra, behind the eye socket.[9]