Bursa of Fabricius

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bursa of Fabricius

[′bər·sə əv fə′brēsh·əs]
(vertebrate zoology)
A thymus-like organ in the form of a diverticulum at the lower end of the alimentary canal in birds.

Bursa of Fabricius


(named after G. Fabricius), a pouchlike thick-walled formation in birds, situated on the dorsal surface of the rear section of the cloaca. The bursa of Fabricius is well developed in all young birds until they reach sexual maturity, at about eight or nine months, when it becomes reduced. Rheas are the only birds in which it does not become reduced. The function of the bursa of Fabricius has not been clearly established; lymphatic cells and oxyphile leucocytes are formed inside it.

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Histopathological lesions in the bursae of Fabricius were demonstrated in this study 4 and 7 weeks after IBD vaccine administration.