Avian stomach anatomy – a mini review

The stomach of birds comprises three parts – glandular (proventriculus gastris), muscular (ventriculus gastris) and pyloric (pars pylorica gastris). Depending on the diet, these three parts are well differentiated in omnivorous, herbivorous, insectivorous and granivorous birds and slightly differentiated in fish- and meateaters. In fruit-eating, nectar-eating and testacivorous birds, the stomach has an intermediate structure between the two types. In some birds from the genus Tangara, the stomach is reduced to a diverticulum.

Micro- and macroanatomical features of the uropygial gland of duck (Anas platyrhynchos) and pigeon (Columba livia)

We describe the morphological, histological and histochemical characteristics of the uropygial gland of the duck (Anas platyrhynchos) and pigeon (Columba livia). The weight and dimensions of the glands were recorded. The gland openings onto the papilla in ducks were surrounded by double tufts of downy feathers; the tufts were held together by an oily secretion. In the pigeon, the gland opening was onto naked skin. Samples for light and transmission electron microscopy were obtained from adult birds. Gland morphometry of the duck showed greater dimensions and relative gland weight than the pigeon. In both species the gland was lined by stratified epithelium, packed with secretary tubules and filled with oil droplets that were discharged into a central cavity. In the pigeon, the gland was branched and alveolar with a wide central lumen, whereas in the duck it was simple and branched tubular. Ultrastructural analysis of both species revealed that the fat globules tended to condense in the peripheral layers of the secretory and degenerative cells, and the nuclei exhibited pyknosis, which suggest the holocrine nature of the gland. Morphometric and histological analysis of the gland showed that the architecture is similar among birds; however, some species-specific differences suggest a functional correlation with the habitat.