Morphological and Histological Study on Vermiform Appendix in Rabbit, Goat and Human Being.

ABSTRACT

Background: The vermiform appendix is a narrow blind tube projecting from the postero-medial wall of caecum. The name is derived from the Latin word "Vermiforma" meaning worm shaped or worm like. Anatomically, it is one of the mobile viscera of abdomen with an average length of 6-8cm. Microscopically, it consists of mucous, sub mucous, muscular and serous coats from inside out, and its surface epithelium being lined with a simple columnar type of cells including Goblet, Paneth and Argentaffine cells. Due to the presence of extensive lymphoid tissue in the mucous and submucous coats forming lymphoid follicles, it has been called 'Tonsil of the Abdomen'. This small structure without any known function in a human being has been regarded as a vestigial remnant of a better developed distal caecum in herbivores. However, in view of its rich blood supply and histological cyto differentiation, the vermiform appendix has been accepted as a complex and highly specialized organ rather than a degenerate vestigial structure. Aim: This study was performed to compare and contrast the morphology and histology of the vermiform appendix in three species of class mammalia with different dietary habits. Methods: Samples of fifty-three human vermiform appendices were collected out of which twenty-three were of human being, seventeen were of goats and thirteen were of rabbit. The samples were subjected to a naked eye examination along with routine histological staining and observation. Results: In man the range of length of vermiform appendix was from 5.4 -12.4 cm. histologically, all four layers were prominent. In goat the length of caecum was from 15 – 28 cm and microscopically all four layers were prominent. In the rabbit length of the vermiform appendix was from 8.5 – 12.5cm and all four layers were observed histologically. Conclusion: Morphological and histological differences as observed in vermiform appendix and caecum of three mammals in this study appear to be associated with their different dietary habits. Morphologically distinct vermiform appendix was found in human being and rabbit only as goat has a well-developed caecum. Rabbit revealed to possess a very large caecum acting as a fermentation tank but also a prominent and distinctive appendix with lymphoid aggregations.