COMPARATIVE HISTOCHEMICAL AND HISTOMORPHOMETRICAL STUDY OF ESOPHAGUS STRUCTURES IN SHEEP (Ovis aries) AND RABBITS (Oryctolagus Cuniculus)

Evolution between animals causes many changes so that it can adapt to its environments. Each species has unique features that help them survive and can consume different types of food. Sheep and rabbits are economically important animals and used in many aspects of veterinary medicine.This study aimed to compare the histomorphometric and histochemical features of the esophagus of twenty sheep (n = 10) and rabbit (n = 10) adult males. The samples were collected from slaughterhouse and market Misan and were used for histological studies of two types of stains, hematoxylin and eosin, and special stains (Periodic acid Schiff stains). Histological study showed differences in the type epithelium of mucosa lining the esophagus between sheep and rabbits. The epithelium lining was composed of a keratinized stratified squamous epithelium in sheep while in rabbit was composed of a non-keratinized stratified squamous. In both animals, the submucosa layer does not possess glands. The muscular layer of both was composed of striated muscle in the cervical, thoracic, and abdomen parts of the esophagus. Both animals contained an outer layer of loose connective tissue called the adventitia. All layers in sheep showed more thickness than in rabbits. The histochemical study showed that the reaction to Periodic acid Schiff stain was similar between the animals and in different places. Only stratum corneum cells of the sheep mucosa and squamous cells of the rabbit mucosa demonstrated a strong reaction to this stain. In contrast, the rest of the cells of the mucosa and muscular layers were moderate reactions with Periodic acid Schiff stain in all regions sheep and rabbit esophagus. Submucosa and adventitia showed weakly reaction with Periodic acid Schiff's stain in both animals. In conclusion, this study showed that sheep and rabbits have similarities and differences in the esophagus; that is, the layers of this organ has different thicknesses and respond differently to Periodic acid Schiff stain.