Abstract:
The glandular regions of the upper digestive tract in the emu were non-pigmented (except for the tongue in most
specimens) and invested by a non-keratinised stratified squamous epithelium. The glands found in these regions
were exclusively simple in nature and composed of tubular secretory units lined by Periodic Acid Schiff Stain-positive
mucus-secreting cells. The naming of the various glandular fields was based on previously identified anatomical
features and on nomenclature modified from previous studies on birds. The glands were classified into two main
types, namely, simple tubular and simple branched tubular mucus-secreting glands. Simple branched tubular glands
were a feature of the regions exposed to the greatest amount of friction during feeding, whereas simple tubular
glands were a feature of regions exposed to less friction. The saliva produced by the salivary glands in birds functions
to moisturize and lubricate food boli. Mucins in saliva also protect mucosal surfaces from desiccation and mechanical
damage, assist in maintaining cellular water balance, provide lubrication and have an antimicrobial action. This study
suggests that, in addition to the role of specific gross anatomical features, the type and distribution of glandular tissue
in the emu upper digestive tract supports the cranioinertial feeding method employed by this species.
