Study On The Histological Structure And Distributive Changes Of Mucosal Immunity-associated Cells In Large Intestine Of The Yak

Yak is a kind of rarely domestic species, it could tolerate high altitude and lowoxygen environment and then reproduce after a long period of natural selection. Yakcould provide meat, milk and other raw materials for farmers and all of these are vitalresource for extremely environment animal production.To reveal the structure of adult yak’s large intestine histological and distributionand varies of mucosal immune related cells, this study adopt the paraffin embeddingsectioning technology, histochemical technology, image analysis, microscopicmeasurement technology and transmission electron microscope to investigate adultyak’s large intestine structure and the number of changes of intraepithelial lymphocytes,goblet cells, plasma cells and mast cells. The results showed that yak large intestinal wallconsists of mucous membrane, submucosa, tunica muscularis and tunica adventitia.Yak cecum epithelial cells was simple columnar cells，striated border was not obvious,lamina propria of cecum contains a lot of isolated lymphoid nodules, germinal centerwas obvious,meanwhile, lamina propria has a lot of adenomas, A large number ofglands were in the lamina propria, glandular epithelial cells closely arranged, whichsandwiching a large number of lynphocytes, the inner circular layer to form specialmuscle summary. Colonic mucous membrane and tunica muscularis were developed,have isolated lymphoid nodule in lamina propria, but less quantity than the cecum. Alarge number of goblet cells were in the rectal mucosa and intestinal glands, the secretion ofmucus proteins which from goblet cells form a protective film on the mucosal surface. Thethickest mucous layer was in colon, mean thickness was864.18±88.46μm, while thethickness of mucous layer of cecum and rectum was606.82±53.89μm and755.86±39.45μm, respectively, remarkable significant difference between colon andrectum (P<0.01); non-significant difference between colon and rectum (P>0.01);non-significant difference between cecum and rectum (P>0.01). The thinnestmuscular layer was in cecum (926.4±24.9μm), non-significant difference (P>0.01)between colon(1026.6±126.6) and rectum(1143.8±157.3). The number ofintraepithelial lymphocyte gradually decreased from colon to rectum and remarkablesignificant difference (P<0.01), non-significant difference between cecum and colon(P>0.01); In terms of mast cell non-significant difference between cecum and colon(P>0.01), remarkable significant difference between colon and rectum, cecum andrectum (P<0.01); Concerned goblet cell non-significant difference between rectumand colon (P>0.01),remarkable significant difference between colon and rectum(P<0.01). Observation of electron microscopy indicated that junctional complexexisted among the epithelium columnar cells such as tight junction, intermediatejunction and desmosome junction, a great deal of microvillis arranged near freesurface. The cytoplasm of intraepithelial lymphocyte was relatively less and nucleiwas round. The cytoplasm of mastocyte contained unequal sized high electron densityparticles aggregation. The cytoplasm of plasmocyte contained lots of roughendoplasmic reticulum. A mount of rough endoplasmic reticulum andribosome nearnuclei of goblet cell, cytoplasm was filled with lots of mucus particles.The tissue structure of large intestinal wall of yak was similar to other ruminant animals basic’s, but each layer had its distinct characteristic. Cecum mucosa laminapropria of isolated lymph nodules which has strong mucosal immune function.Because muscle summary increases the ductility of cecum,it is advantageous that theyaks Storage and fermentation of food and enhance their ability to adapt in alpineHypoxia grassland environment. The junctional complexes between epithelial cells ofYak constitute important physical barrier function of the body, it could transportrelated substances selectively,maintain the integrity of mucosal barrier throughpreventing bacterial, antigen substances or toxins into the lamina propria.The regulardistribution of mucosal immunity-associated cells in each segment of large intestineprovide a good immune barrier function for large intestine.