Anatomical, histological, and scanning electron microscopic features of the esophagus and crop in young and adult domestic pigeons (Columba livia Domestica)

Abstract Background Pigeons (Columba livia) are mainly raised as a source of animal protein, racing, leisure and as an experimental animal. The present study investigated the morphology of the esophagus in the young and adult domestic pigeon, Columba livia domestica. Methods Ten young and ten adult, normal, and healthy pigeons were collected from the local breeders. Samples from different parts of esophagus and crop were examined grossly, by stereomicroscopy, scanning and light microscopy. Results The esophagus consisted of a long cervical part, a crop, and a short thoracic part. The crop was represented by a thin-walled outpouching with two lateral diverticula. The mucosa presented wavy fine folds in the cervical esophagus, irregular folds in the lateral diverticula giving it a corrugated appearance, and prominent longitudinal folds with several gland openings in the middle and lower parts of the crop, as well as in the thoracic esophagus. The density of gland openings was higher in adult pigeons than that in young pigeons. The mucosa of the esophagus was lined by non-keratinized stratified squamous epithelium. The shape, height, and branching of the mucosal folds differed between young and adult pigeons. Mucous-secreting alveoli were detected in the middle part of the crop as well as in the thoracic esophagus, but not in the cervical esophagus or lateral diverticula of the crop. Conclusion The variations between the young and adult pigeons suggest a functional adaptation of adult pigeons to their diet compared to young pigeons.