Histological Description of Morphogenesis of the Gastroesophageal Mucosa of Gallus gallus domesticus (Linnaeus, 1758)

Abstract

SUMMARY:The ontogenesis of the gastroesophageal mucosa involves morphological alterations related to its structure and the function of each segment. The present study describes the histogenesis of the mucus-secreting epithelium and glands of the esophagus, gizzard, and proventriculus of the chicken (Gallus gallus), and identifies alterations in the secretion pattern of glycosaminoglycans (GAG's). We analyzed 38 chicken embryos, processed the material collected following the histological routine, and then stained it with hematoxylin-eosin for the analysis of tissue structure and with Gomori's trichrome for the identification of conjunctive tissue and collagen fibers. We used the PAS histochemical technique for the analysis of neutral GAG's and the AB pH 2.5 histochemical technique for the analysis of acid GAG's. The embryos at late stage of development had the esophagus wall composed of four layers: mucosa, submucosa, muscularis, and serosa, whereas the proventriculus and the gizzard were composed of three layers: mucosa, muscularis, and serosa. In all three segments, we identified the superficial epithelium as mucus-secreting; in the esophagus this epithelium was mucussecreting only at the initial development stages. The proventricular glands began to form at the initial development stages, whereas the tubular glands began to form in the gizzard just after the 15th day. The differences in the production of GAG's in these regions of the digestive tract are related to development stages, functions, and physiological requirements of each segment, and to the gradual adjustment of the body to the post-hatching life.

Histochemical study of the oesophagus in the chukar partridge (Alectoris chukar) embryo

“…Only on the 20 th day the cells of the glands became characteristic of mucous glands: tall and with nucleus located at the basal region. It is not clear that these results belong to the cervical or thoracic part of the oesophagus as they had not mentioned it in their study [13].…”

“…In the 20-day turkey, buds were present throughout the oesophagus and crop, but glands with lumen were present only in the thoracic part [5]. Ventura et al [13] stated that the primordia of oesophageal glands of the chick embryo were already present on the 12 th day of development. From the 16 th day on, the cells that formed the oesophageal glands organised themselves in 1 or 2 layers around the lumen.…”

“…On the contrary, Ivey and Edgar [5] reported the epithelium appeared to be somewhat horny in the pharynx, oesophagus, and crop of the 20-day chick embryo. However, in 2013, Ventura et al [13] stated that the mucosa of the chicken oesophagus in 12-to 20-day-old embryos was covered by non-keratinised and secreting squamous stratified epithelium.…”

“…The avian oesophagus had also been the subject of this kind of studies, which most of them focused on the chicken embryo. Turkey, guinea fowl, pigeon and a few other birds species were also studied [4,5,13].…”

“…Consequently, these differences result from different sequential events of the oesophagus histogenesis in these two classes of animals. Although the histogenesis of the oesophagus has been studied in some avian species [5,13], differences in their nutritional behaviour, length of incubation period and evolutionary origin of avian species result in different time and sequence of the morphogenetic events of the oesophagus formation and have been prevented researchers to introduce a common "model of oesophagus hitogenesis" for them.…”