Abstract
Background:
The esophagus is vital for the efficient transport of food from the mouth to the stomach. It features mucous membrane and muscle fiber layers that are essential for generating powerful peristaltic movements to propel food forward. Additionally, the inner lining of the esophagus comprises specialized epithelial cells specifically designed to handle the passage of both rough and smooth food types with ease.

Aim:
The current study was aimed as a comparative model for investigating the changes that occur in the esophagus cytoarchitecture of the same animal species.

Methods:
Tissue specimens were processed according to the protocol of the paraffin embedding technique and stained with hematoxylin and eosin and Masson’s streptomycin (Masson’s trichrome).

Results:
In this study, the esophagi of lactating, weaned, and adult cats were used to investigate histological and histochemical features. The esophagus wall of lactating kittens revealed immature cytoarchitecture of all tunicae with little mucosal folds covered by proliferating epithelial cells, the muscularis mucosa was absent, and the muscularis externa comprised a bilayer of newly differentiating smooth myofibers. In weaned kittens, the esophagus had a slightly thickened wall, the mucosa of the cervical and thoracic segments had long folds, and the thoracic and abdominal segments revealed differentiation of the muscularis mucosa and skeletal muscle fibers, which differentiated in the cervical and thoracic segments, while the muscularis revealed smooth muscle bundles in the abdominal segments. In mature cats, the mucosa of the entire length of the esophagus comprised enlarged mucosal folds that were covered by very thick stratified squamous cells. The lamina propria submucosa had no esophageal glands. Muscular mucosa was absent in the cervical segment, whereas it was observed in the thoracic and abdominal segments. The muscularis externa at the neck and chest segments of the esophagus is constructed of inner circular and outer longitudinal bundles of skeletal muscle, whereas it turns into smooth muscle fibers in the abdominal segment. The statistical analysis of the data revealed significant differences in fold height and epithelium, fold thickness, and tunica muscularis among segments in weaned, lactating, and adult cats.

Conclusion:
The current study concluded that the cat esophagus was not a glandular part of the gastrointestinal tract compared with other mammals, which makes this species a reliable experimental model of digestive tissue, and explained the role of the pharyngeal or oral part of the digestive system in the lubrication of the upper digestive tract.

Key words: Esophagus; Histochemical; Cats; Kitten.