MORPHOLOGICAL, HISTOLOGICAL, AND HISTOCHEMICAL STUDIES OF STOMACH, PROVENTRICULUS, AND GIZZARD IN SLENDER-BILLED GULL CHROICOCEPHALUS GENEI (BRÈME, 1839) (AVES, CHARADRIIFORMES, LARIDAE)

The current study aimed to identify the morphological, histological, and histochemical composition of the proventriculus and the gizzard of the slender-billed gull Chroicocephalus genei (Breme, 1839) (Aves, Charadriiformes, Laridae) using a light microscope. Morphological analysis revealed that the stomach of the bird is divided into proventriculus and gizzard. The proventriculus is situated to the left of the body's midline and is completely encompassed by the liver's left lobe, and appears pear-shaped or elongated oval and has smooth walls. The gizzard has a pear-shaped muscular organ and is located to the left of the midline in the lower quarter of the abdominal cavity. The results of histological examination show that there are four major layers that make up the proventriculus and gizzard walls consist of: mucosa, submucosa, muscularis, and serosa, as well as the presence of the koilin layer covering the tunica mucosa of the gizzard. The lining epithelium of the wall of the proventriculus is covered with simple columnar epithelial tissue, but the lamina properia has simple tubular glands and is made mostly of loose connective tissue, and the submucosa is composed of loose connective tissue and deep gastric glands. The muscularis which consist of three layers of smooth muscle fibers, while loose connective tissue makes up the tunica serosa. In the gizzard, the lining epithelium is lined by simple columnar epithelium; the lamina properia consists of simple tubular glands. The gizzard's submucosa is lined with dense connective tissue, the muscularis is made up of smooth muscle fibers, and the tunica serosa is coated with loose connective tissue. According to the histochemical analysis, the proventriculus and gizzard contain a significant amount of mucopolysaccharides which exhibited a positive reaction to Periodic Acid Schiff (PAS) stains.