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

Abstract

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. 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.