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العنوان
Anatomical, Histological and Ultrastructural Studies
on the Rectal Caeca of Some Avian Species /
المؤلف
Ali, Shahenda Gamal Mohamed.
هيئة الاعداد
باحث / شاهندا جمال محمد علي
مشرف / رجاء محمود الديب
مناقش / سهام بيومى سالم محمد
مناقش / أحمد إمام أحمد دكرورى
تاريخ النشر
2022.
عدد الصفحات
238 P. :
اللغة
الإنجليزية
الدرجة
ماجستير
التخصص
علم الحيوان والطب البيطري
تاريخ الإجازة
1/1/2022
مكان الإجازة
جامعة عين شمس - كلية العلوم - قسم علم الحيوان
الفهرس
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Abstract

The current work was undertaken to assess, in a comparative manner, the anatomy, histology and ultrastructure of the rectal caeca of six avian species avian species with three different feeding habits; the carnivorous, omnivorous and granivorous habits. The carnivorous birds were the black winged kite, Elanus caeruleus, the common kestrel, Falco tinnunculus rupicolaeformis and the barn owl, Tyto alba. The omnivorous birds were the hooded crow, Corvus corone cornix and the common moorhen, Gallinula chloropus. Finally, the granivorous bird was the zebra finch, Taeniopygia guttata. The data were then used to explore the relationships between the rectal caeca structure and the feeding habits and the taxonomical position.
In the present work, the rectal caeca of all studied avian species are represented by a pair of pouches that arise from the alimentary canal at the ileocecocolic junction. The length of the rectal caeca of the studied species was variable. In this regard, the rectal caeca of E. caeruleus, F. t. rupicolaeformis, C. c. cornix and T. guttata were a short and finger-like pair. On the other hand, those of T. alba and G. chloropus were a long pair and each caecum was divided into three parts; the proximal, middle and distal parts.
The relative caecal lengths to the intestinal length and rectal length of E. caeruleus, F. t. rupicolaeformis, C. c. cornix and T. guttata were small, while those of T. alba and G. chloropus were large.
The histological results revealed that the rectal caeca of E. caeruleus, F. t. rupicolaeformis, C. c. cornix and T. guttata were of lymphoid type, while those of T. alba and G. chloropus were of the intestinal type. Moreover, the wall of the rectal caeca of all studied species was built up mainly of four layers; the serosa, muscularis, submucosa, and mucosa. In addition, the wall of the rectal caeca of F. t. rupicolaeformis had an additional layer; the sub-serosa.
The muscularis of E. caeruleus, T. alba, C. c. cornix and G. chloropus was thick and was formed of two muscle layers, namely: the outer longitudinal and inner circular muscle layers, however, the muscularis of F. t. rupicolaeformis and T. guttata was formed of a single thin layer of longitudinal muscle fibers.
The mucosal layer of the rectal caeca of all studied species consisted of two layers; the lamina propria and the epithelial layer. Besides, the mucosa of the rectal caeca of T. alba and G. chloropus was thrown into numerous villi, which were lined by a simple columnar epithelium and numerous goblet cells. The villi of the middle part of the rectal caeca of G. chloropus were longer than those of the other two parts.
The lamina propria E. caeruleus, F. t. rupicolaeformis, C. c. cornix and T. guttata was formed of a connective tissue that was filled with numerous lymphocytes and few crypts of Lieberkühn. On the other hand, the lamina propria of T. alba and G. chloropus was formed of a connective tissue that contained scattered lymphocytes and numerous crypts of Lieberkühn. The crypts of Lieberkühn were lined by a simple columnar epithelium. In addition, the lamina propria of the middle part of the rectal caeca of T. alba and the proximal part of the rectal caeca of G. chloropus were characterized by the presence of the lymphoid nodule which were formed of lymphocytes aggregation.
The epithelial layer of the rectal caeca of all studied species, except F. t. rupicolaeformis, was built up mainly of a simple columnar epithelium that had scattered goblet cells. It is noteworthy to mention that the epithelial layer of the rectal caeca of F. t. rupicolaeformis was devoid of goblet cells.
The ultrastructural examination of the mucosal layer of the rectal caeca of F. t. rupicolaeformis and G. chloropus revealed that it was divided into two layers; namely: the epithelial layer and the lamina propria.
The epithelial layer of the mucosa of F. t. rupicolaeformis was built up mainly of enterocytes and scattered M-cells, while that of G. chloropus consisted mainly of enterocytes and goblet cells.
The enterocytes of F. t. rupicolaeformis and G. chloropus were columnar cells (the average height is of about 15 and 20 µm, respectively) with oval nuclei that had prominent eccentric nucleoli and chromatin patches. The enterocytes cytoplasm contained numerous mitochondria and rough endoplasmic reticulum. The luminal cell membrane of such enterocytes was characterized by presence of numerous microvilli. The microvilli length of F. t. rupicolaeformis was about 700 nm, while that of G. chloropus was varied in different part of the rectal caeca. In this context, the microvilli length of the enterocytes of the proximal and middle parts of the rectal caeca was of uniform length of about 1 µm, while that of the distal part was about 600 nm.
The M-cells of F. t. rupicolaeformis were modified enterocytes that are characterized by their high electron density. The luminal cell membrane of these cells had numerous microvilli, whose length was about 700 nm and had a prominent glycocalyx. It is noteworthy to mention that the lymphocytes are seen near the basal part of the M-cells.
The lamina propria of the rectal caeca of F. t. rupicolaeformis was formed of connective tissue that was filled with numerous lymphocytes and few crypts of Lieberkühn. Furthermore, there were two types of the lymphocytes, according to their size and electron density, the large and small lymphocytes.
The lamina propria of G. chloropus was formed of connective tissue that had numerous crypts of Lieberkühn, which are built up mainly of enterocytes. Moreover, the lamina propria of the proximal region of the rectal caeca of G. chloropus was characterized by the presence of lymphoid nodule which was formed of numerous lymphocytes of the small type.
The results of the present work indicated that the rectal caeca of the carnivorous E. caeruleus and F. t. rupicolaeformis were small and play a major role in the immune response against foreign microorganisms and has no role in food digestion and absorption. On the contrary, the rectal caeca of the carnivorous T. alba were unexpectedly long and well-developed. Such rectal caeca may be implicated in food absorption or may be associated with the conservation of critical resources such as water and nitrogen.
Moreover, the present results showed that the rectal caeca of the omnivorous C. c. cornix were small, however those of the omnivorous G. chloropus were long and well-developed. In addition, the rectal caeca of the granivorous T. guttata were small. The unexpected small rectal caeca of C. c. cornix and T. guttata may be likely due to the animal-heavy diet of C. c. cornix or due to that the species of Order: Passeriformes have small rectal caeca regardless of their feeding habits. Moreover, the expected well-developed rectal caeca of G. chloropus may be due to its plant-heavy diet.
In conclusion, the present study did not fully agree with the general concept that postulated that the herbivorous, omnivorous, and granivorous species had the longest rectal caeca than their carnivorous counterpart because the animal diets are easily digested by endogenous digestive enzymes. In the present work, the anatomical, histological and ultrastructural characteristics of the rectal caeca of all studied avian species proved that the differences between the rectal caeca do not dependent only on their feeding habits, but also on their taxonomical position. The rectal caeca are poorly-developed in Accipitriformes, Falconiformes and Passeriformes. On the other hand, the well-developed rectal caeca occur in the Strigiformes and Gruiformes.
The current work recommends conducting more studies on the structure of the avian rectal caeca of different avian orders and find out the relationships between the rectal caeca structure, function and the bird taxonomical position.