Functional Morphology of the Upper and Lower Eyelids, Third Eyelid, Lacrimal Gland and Superficial Gland of the Third Eyelid in the Red Kangaroo (Macropus rufus).

A study concerning the upper (UE) and lower (LE) eyelids, lacrimal gland (LG), superficial gland of the third eyelid (SGTE) and third eyelid (TE) was conducted on 4 sexually mature red kangaroos (2 males and 2 females). Gross anatomical, histological, histometrical, histochemical and ultrastructural (TEM) components were compared. Tissue sections were stained with haematoxylin and eosin, azan-trichrome, van Gieson, Masson-Goldner trichrome, methyl green-pyronin Y, periodic acid-Schiff, alcian blue pH 2.5, aldehyde fuchsin and Hale's dialysed iron. The location of the LG, SGTE, TE, UE and LE was similar to that of other mammals. Organized lymphoid follicles were also found in the LE. The TE resembled the letter T and was composed of cartilage (hyaline tissue). The LG was relatively larger than the SGTE. The LG and SGTE were multilobar tubuloacinar glands. The LG had more plasma cells than the SGTE. The SGTE and LG secretions were mucoserous in composition. The TEM study showed that the secretory cells of the LG and SGTE have a similar ultrastructural appearance. Two types of secretory vesicles were detected in the cytoplasm in acini and one type of secretory vesicle was found in the tubules of these glands.