Page 256 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

238 Veterinary Histology of Domestic Mammals and Birds

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10.88 Gall bladder (chicken). Haematoxylin and eosin 10.89 Pancreas (chicken). Haematoxylin and eosin stain
stain (x42). (x300).

to the pancreatic juice are carboxypeptidases, phospholi- Species variation
pases, amylases, collagenases and esterases (from the Golgi
apparatus and endoplasmic reticulum), as well as water Birds: The gall bladder lies on the facies visceralis of
and electrolytes. Within the pancreas, enzymes are present the right lobe of the liver. Many varieties of pigeons
in their inactive form, becoming activated by secretions of and parrots lack a gall bladder. Where present, the
the intestinal mucosa. The synthesis and secretion of pan- gall bladder exhibits a structure similar to that of mam-
creatic juice components is stimulated by the vagus nerve, mals (Figure 10.88).
and by gastrin, secretin and cholecystokinin. The secretions of the exocrine portion of the avian
Centro-acinar cells, considered components of the pancreas pass via three ducts (ductus pancreaticus
intercalated ducts, frequently extend into the acinar end dorsalis, ventralis and accessorius) into the ascending
pieces (Figures 10.84 and 10.87). The epithelium of the duodenum. As in mammals, the endocrine portion
intercalated duct (ductus intercalatus) is simple cuboidal. (Figure 10.89), the islets of Langerhans, produce insu-
Intercalated ducts are continued by intralobular ducts. lin, glucagon and somatostatin. The islets are largest
There are no striated ducts. The epithelium of the larger and most numerous in the splenic lobe of the pancreas.
interlobular ducts is columnar and often contains goblet
cells. The ducts are surrounded by loose networks of colla-
gen fibres containing blood vessels and nerve fibre bundles.

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