Light and electron microscopic study of the eyelids, conjunctiva-associated lymphoid tissue and lacrimal gland in Bilgorajska Goose (Anser anser)

Normal structure of the accessory organs of the eye is essential for normal eye physiology. Among the most important accessory organs of the eye are the eyelids, the conjunctiva-associated lymphoid tissue (CALT) and the lacrimal gland (LG). The aim of this study was to demonstrate the histological structure of the eyelids and LG by histochemical and ultrastructural analysis. The study was performed on 13 adult female Bilgorajska geese. Eyelid samples were stained with the Alcian blue (AB pH 2.5) and periodic acid-Schiff (PAS) methods. Staining methods used for LG were AB pH 2.5, aldehyde fuchsin (AF), PAS and Hale’s dialysed iron (HDI). Within the connective tissue of the eyelids, well-developed, diffuse, CALT follicles were observed, mostly under the conjunctival epithelium. Numerous lymphocytes were present within loose connective tissue. Staining of the eyelids with the PAS method demonstrated the presence of goblet cells of a mucous nature, and AB pH 2.5 staining indicated the presence of sulfated acid mucopolysaccharides. PAS staining of LG revealed the presence of secretory cells containing weakly PAS-positive granules. All epithelial cells of the corpus glandulae and the duct systems reacted positively to AB pH 2.5. HDI staining detected the presence of carboxylated acid mucopolysaccharides. Transmission electron microscopy investigations revealed two types of secretory epithelial cells in LG. Both types of LG cells contained drop-like secretory vesicles of different sizes with low or high electron density in cytoplasm, as well as small and large lipid vacuoles, and numerous small primary lysosomes.