The morphology of the starling (Sturnus vulgaris) bursa of Fabricius: a scanning and light microscope study.

Two starlings, a male and female, were sampled from the nest in 1980 and 1981. Scanning electron microscopy and light microscopy revealed the bursa of Fabricius to be similar in these two nestlings. In the center of the elongated bursa is a wide central canal from which blind secondary canals branch. The luminal surface of the central canal is smooth and lacks the plicae characteristically observed in the chicken's bursa. The central and secondary canals contain a mixture of epithelial cells: mucin-producing goblet cells and epithelial cells with deeply stained granules. The former cells are present in the chicken's bursa while the latter cells are not. These epithelial cells lack the florid microvilli observed in the chicken's interfollicular epithelium. The secondary canals are lined by bursal follicles which are divided into a cortex and medulla by epithelial cells. The epithelial cells of the corticomedullary border form an arch which partly encloses lymphocytes. A row of lymphoblasts commonly line the archlike epithelial cells. Follicle-associated epithelium (FAE) appears at the apex of the bursal follicle. Unlike the chicken, one may observe tingible-body macrophages associating with the FAE. A prominent terminal web is located beneath the apical surface of the FAE.