Histoarchitecture of Large Intestine and Lympho Glandular Complex of Pig

Abstract

Background: To have a better understanding of the lympho glandular complexes (LGC) along with the histoarchitecture of large intestine and associated M cells, the proposed study have been undertaken. Methods: Present study was conducted on 12 (twelve) numbers of apparently healthy weaned crossbred piglets of 3 to 4 months irrespective of sex. After humane sacrifice of the animals with the approval of institutional animal ethics committee, the representative tissue samples were collected preserved, processed and stained as per standard methods of Luna (1968). Result: Columnar cells predominated the follicle associated epithelium (FAE) and the crypts. M cells were recorded in the follicle associated epithelium as well as in lower crypt epithelium in toluidine blue stained ultra thin sections. M cells were observed with intraepithelial lymphocyte and basally placed euchromatic nucleus. In the colon and rectum of crossbred pigs the lympho glandular complex (LGC) typically consisted of a pore like depression on surface epithelium from which extensions of mucosal glands passed through the circular gap into lamina muscularis mucosae. The lymphatic aggregation of LGC in the lamina propria and tunica submucosa showed three distinct zone viz. follicle, interfollicular area and dome area and distinct FAE could be appreciated. The epithelium lining the solitary lymphatic nodule (SLN) showed (Periodic acid-Schiff) PAS positive reaction. The mucous substance showed strong reaction in the gland in LGC and the FAE epithelium the number of goblet was less. The LGC was formed by aggregation of lymphoid follicles with invagination of crypt gland inside the follicle in the tunica sub mucosa. The follicle associated epithelium devoid of goblet cells were observed on the LGC with interspersed of diffuse migrating lymphocytes in the lamina propria. In the LGC, secondary follicle with interfollicular area was appreciated. In mesenteric lymph node the secondary follicles with inner germinal centre and outer corona could be seen in cortico medullary area. Meshwork of reticular fibers was abundantly present around the crypts in the lamina propria and in the pore like depression of LGC and around the secondary follicle. Collagen fibers could be seen surrounding the LGC and glands. Scanty collagen fibres were observed in the inter-follicular glands. Innervations of nerve fibre was observed around the lymphoid follicle and penetrating the LGC. The mucosal glands were PAS positive.