Comprehensive Structural Characterization of the Esophageo‐Gastric Tube in the Hooded Crow ( <i>Corvus cornix</i> ): Histological, Histochemical, and Ultrastructural Insights

The esophagus and stomach of nine adult healthy hooded crows (Corvus cornix) were collected for light and scanning electron microscopes (SEM) as well as histomorphometric analysis. SEM showed that the esophageal mucosa has round-shaped gland openings, extending to its junction with the proventriculus. The proventriculus luminal surface had roughly circular gland openings surrounded by simple mucosal folds that appeared as raised tubular structures. A cuticle at the proventricular-gizzard junction was present. The gizzard cuticle appeared as thread-like rods, while the tubular gastric glands resembled broccoli sprouts. Histologically, the esophageal mucosa exhibited argyrophilic endocrine cells within both the lining epithelium and glandular epithelium. Numerous telocytes surrounded the secretory acini of the superficial and deep proventricular glands and encircled blood vessels in the lamina propria. Columnar to cuboidal (oxynticopeptic) cells were abundant in the deep proventricular glands. The most superficial epithelial cells of the gizzard contained excessive metachromatic granules. Telocytes were detected around the glandular secretory acini within the lamina propria and muscle fibers of the gizzard. The results of the current study suggest that the esophageo-gastric tube histomorphology in hooded crows revealed some characteristics that might be attributed to adaptation to a diverse urban and rural diet.