The histogenesis of the esophagus and crop of the chicken, turkey, guinea fowl and pigeon, with special reference to ciliated epithelium

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

“…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].…”

“…Schumacher [12] described the oesophagus of the fowl as having a pseudostratified epithelium at 5 th day, low columnar at 7 th day, 2-layered cuboidal at 9 th day, and 4-layered stratified squamous at 18 th day. Ivey and Edgar [5] reported that the oesophageal epithelium of the chicken, turkey, guinea fowl and pigeon was simple columnar or rarely pseudostratified type in the youngest embryos. They described the elder embryos oesophagus with 2-layered cuboidal epithelium and sometimes, the surface layer stretched into the squamous type.…”

“…There was a gradual increase in the number of cell layers, with the surface layer assuming a squamous form in some cases and a columnar or cuboidal type in others. The squamous type of surface cell became more common in later stages [5].…”

“…In the mammals, it is a muscular tube modified for voluntary and involuntary movement of foodstuffs to and from the stomach [2]. The oesophagus of birds shows histologic differences with that of mammals including glandular lamina propria [1,2], different extension of muscularis mucosae into the mucosal folds [5,9,11], absence of muscularis mucosa in some birds [5,10] and two external smooth muscular layers covered almost completely by the adventitia [1,2]. Consequently, these differences result from different sequential events of the oesophagus histogenesis in these two classes of animals.…”

“…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.…”