Keywords
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| Anatomy; Animal; Animal Structures; Endocrine Glands; Geese; Histology; Histology, Comparative; Islets of Langerhans; Microscopy; Pancreas; Pancreatic Ducts |
INTRODUCTION
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| The avian pancreas is located on the right side of the abdominal cavity in all birds. It is tightly bound by mesentery and blood vessels positioned between the descending and the ascending duodenal loops [1]. It is composed of two main lobes, dorsal and ventral, which extend from the apex of the duodenal loop to the point where the pancreatic ducts enter the distal duodenum. Another smaller lobe, extending from the head of the pancreas towards the spleen has been termed as the splenic lobe [2]. A further subdivision of the lobes of the pancreas has been made by Mikami and Ono [3] who divide the ventral lobe into the ventral lobe proper and the third lobe on the basis of the latter’s independent form and peculiar distribution of islets. Both dorsal and ventral lobes have ducts extending almost the full length of their course and there is also a third, smaller duct leading from the third lobe. Pancreatic ducts from the acinus to the point where it empties its contents into the duodenum are arranged in following order: intercalated ducts (the smallest in size), intralobular ducts, interlobular ducts and pancreatic ducts (main ducts) [4, 5]. The objective of the present study was to investigate the histological structure of goose pancreatic ducts. |
MATERIALS AND METHODS
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| Five adult geese (Anser anser) obtained from the Kafkas University Veterinary Faculty Farm were used in the current study. Tissue samples from the lobes and ducts of the pancreas were dissected under deep ether anesthesia. Samples were fixed in Bouin’s fluid and then routinely processed for embedding in paraffin. Tissue blocks were cut into 6-micrometer thick sections using a microtome. The sections were stained using Crossmon’s connective tissue method for general observations and Gomori’s method for pancreatic islet cells. |
ETHICS
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| Tissues were harvested in compliance with an approved Kafkas University Animal Care and Use Committee Protocol. |
RESULTS
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| In the present study, the goose pancreas was found to be located between the duodenal loops and had dorsal, ventral, third and splenic lobes. All the pancreatic lobes had their own intercalated ducts, intralobular ducts (Figure 1) and interlobular ducts (Figure 2). In addition, there were only two main ducts (dorsal and ventral pancreatic ducts) extending from the pancreas (Figure 3) to the point where it emptied its contents into the duodenum. |
| Intercalated ducts lined with a simple flattened epithelium reach intralobular ducts lined with tall columnar epithelium. Intralobular and interlobular ducts are composed of two main tissues, a columnar epithelium which lines up inside the ducts and connective tissue surrounding outside the ducts. Furthermore, interlobular ducts have thin muscle layers surrounding the connective tissue. However, the main ducts of the pancreas are composed of three layers: first, the mucosa lined with columnar epithelial tissue, then inside longitudinally and outside circularly arranged muscle tissue and, finally, externally adventitial connective tissue. Furthermore, basophilic staining on the apical surface of the goose pancreatic ducts starting from the interlobular ducts (Figure 2) to the pancreatic ducts (Figures 3 and 4) indicates possible secreting functions of those tissues. |
| Interestingly, the glands were found intermittently inside the connective tissue of the ducts starting from the interlobular ducts (Figure 2) to the point where the pancreas emptied its contents into the duodenum (Figure 5) as well as inside the muscular layer of the pancreatic ducts (Figure 3). Those glands contained centro-acinar cells (Figure 6) and also had the same staining features as the acinus. Moreover, those glands had their own intercalated ducts (Figure 4), intralobular ducts (Figure 5) and interlobular ducts (Figure 3). It appeared that the glands inside the wall of the ducts were structurally similar to the exocrine part of the goose pancreas. Furthermore, no endocrine island was noticed among those glands. |
DISCUSSION
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| We found that the goose pancreas, as in other avian species [2], was located between the duodenal loops and had dorsal, ventral, third and splenic lobes. Mikami and Ono [3] demonstrated that the dorsal, ventral and third lobes had their own ducts, whereas Mc Leod et al. [6] showed that the third lobe occasionally consisted of its own duct. Additionally, it was shown that there were usually two pancreatic ducts (main ducts) in the goose pancreas, even though the presence of a third one was reported [7]. |
| We also demonstrated that, in the goose pancreas, there were only two main ducts extending from the pancreas to the duodenum. This finding is in agreement with the results of Mc Leod et al. [6], and Nickel-Schummer and Seiferle [7]. |
| The structure of the goose exocrine glands found in the present study agrees with the results of previous studies [3, 4, 8, 9, 10]. In fact, as in other vertebrates, the avian pancreas was mainly composed of exocrine glands (about 99%), [3, 8]. Those glands consisted of tall columnar epithelial tissues which had acidophilic zymogen granules on their apical surface [4, 9, 10]. Moreover, small centro-acinar cells without granules were observed in the central lumen of the acinus [10]. |
| The structure of the ducts in the goose pancreas was found to be similar to that described in previous studies [4, 11]. In addition, the presence of basophilic staining on the apical surface of the goose pancreatic ducts starting from the interlobular ducts to the pancreatic ducts was also found in chickens [12]. |
| To our knowledge, this was the first report of the presence of glands in the ducts of the goose pancreas. Thus, it would be of interest to study in more detail the structure of those glands using either electron microscopic or immunohistochemical techniques to clarify their possible functions. |
Figures at a glance
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Figure 2 |
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Figure 5 |
Figure 6 |
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References
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