<div>Background: The gut mucosa is effectively protected by a local organization of lymphoid tissue. In large intestine, isolated lymphoid follicles give rise to solitary lymphoid nodules and lympho glandular complexes, which are responsible for sampling of gut antigen and production of local immunity. Large intestine requires higher level of mucosal protection as because it is the site where food staff remains for a longer period and also for ascending rectal infection. Present study was undertaken highlighting the lymphatic drainage from large intestine and solitary lymphoid nodules of pig. 
 
Methods: 1% solution of methylene blue up to 100 micro litters in the one place of submucosa of large intestine as per the standard technique advocated by Smedley et al. (2014) and then stained nearest mesenteric lymph nodes were recorded and re-injected to map the drainage to the next draining lymph node to trace the lymphatic tract. 
 
Result: The study was designed on 12 (Twelve) apparently healthy weaned crossbred piglets of 3 to 4 months age irrespective of sex. Gross study revealed the presence of two different types of solitary lymphatic nodules (SLN) viz.&nbsp;scrotiform and faviform. The scrotiform SLN consisted of central small pore was appreciated in colon and rectum, whereas the faviform SLN although present in colon and rectum was devoid of a central pore. The average solitary lymphoid nodules in the large intestine was 427, of which 403 in colon and 24 in rectum and in terminal part of rectum patches of solitary lymphoid nodules of more than 100 numbers were observed. The different lymph nodes involved in the lymphatic drainage of large intestine of pig were colic caecal, anorectal , lumbar aortic, renal , medial lumbar and lateral lumbar lymph nodes. Again, except the right and left lumbar duct, one minor lymphatic trunk was observed parallel to the rectum, draining the lymph from anorecral lymph node to caudal mesenteric lymph node and then to renal lymph node. The celiac trunk and the jejunal trunk joined and formed a common trunk which was again joined by the colic trunk that finally opened into the caudal aspect of cysternachyli.</div>

Lymphatic Drainage Conduit and Macro Anatomy of Lymphoid System in Large Intestine of Post Weaned Pigs

Background: Gut-associated lymphoid tissue (GALT) in pig comprises the Peyer&rsquo;s patches (PP) in the small intestine and solitary lymphoid nodules (SLN) in the large intestine. The dome epithelium that lines the lymphoid follicles of PP and SLN is specially designed for the uptake of gut luminal antigen where M cell is the principal cell type responsible for antigen uptake and processing.&nbsp; 
 
Methods: In porcine, the M cells were detected in cryosections with the help of FITC-labelled anti-cytokeratin-18 antibody.&nbsp; 
 
Result: The relative distribution pattern of this cell type reflected the possible difference in the microbial environment and, necessity of protective or tolerogenic response against the gut luminal antigens in small and large intestines. It also revealed the preferred location of uptake of mucosal antigen. The number of M cells was highest in the ileum and rectum in the small and large intestine respectively. These cells were mainly confined to the follicle-associated epithelium of the intestinal lymphoid aggregated. However, M cells were also observed in absorptive villi epithelium and in the villi epithelium where lamina propria lymphocytes were more in number.

Relative Distribution of M Cell in the Follicle-associated Epithelium of Peyer&rsquo;s Patch and Solitary Lymphoid Nodule of Porcine Intestines

<div>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).&nbsp;&nbsp; 
 
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.</div>

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Lymphatic Drainage Conduit and Macro Anatomy of Lymphoid System in Large Intestine of Post Weaned Pigs

Relative Distribution of M Cell in the Follicle-associated Epithelium of Peyer’s Patch and Solitary Lymphoid Nodule of Porcine Intestines

Histoarchitecture of Large Intestine and Lympho Glandular Complex of Pig