Histomorphometric Adaptation of Yak (Bos grunniens) Abomasum to the Qinghai-Tibetan Plateau Environment

Six abomasums of yaks (Bosgrunniens) were studied with gross dissection and histological methods. It was found that the mucosa of the yak abomasum was covered with simple columnar epithelium. There were lots of spiral folds (10) in the fundic glandular area. The developed membrane of lamina propria was occupied by high density glands. According to the morphological characteristics of the glands, the abomasum was divided into the cardiac, gastric and pyloric glands. Cardiac glands were curved tubular glands with the intumescent bottom and small glandular cavity. Fundic glands were simple tubular glands or branched tubular glands, where the chief, parietal and mucous neck cells can be observed clearly. Pyloric glands were curled tubular glands, the closer to the deep of the lamina propria, the more obvious the glands curl. Staining of glycoconjugate revealed that the mucosal epithelium of the cardiac gastric and pyloric glands and gastric pits epithelium mainly secreted neutral glycoconjugate, but other portions of cardiac and gastric glands secreted mixed and acid glycoconjugate respectively. By Gordon-Sweet's reticular fiber staining, it was found that the mucous neck cells possessed the characteristic of argyrophilic phenomenon. There was a large number of argyrophilic granules in the supranuclear cytoplasm in contrast with the chief cells. Furthermore, there were isolated lymphoid nodules and diffuse lymphoid tissue in the abomasum glands, especially in corpus abomasi. Grimelius silver staining showed that the argyrophil cells were located in the glandular epithelium and lamina propria of glands, which can also be observed in connective tissue. These endocrine cells dispersed individually in epithelial cells, occasionally in 3­5 cell groups. Therefore, the yaks were grazed throughout the year on diverse natural grassland and had evolved morphological characteristics of the abomasum enabling them to consume a wide variety of plant species, thereby better adapting them to harsh plateau environment.(AU) Seis abomaso yak (Bosgrunniens) fueron estudiados con diseccion y metodos histologicos. Se encontro que la mucosa del abomaso yak estaba cubierta de epitelio columnar simple. Se observaron pliegues en espiral (10) en la zona glandular fundica. La membrana desarrollada de la lamina propia contenia glandulas de alta densidad. De acuerdo con las caracteristicas morfologicas de las glandulas, el abomaso se dividio en las glandulas cardiacas, gastricas y pilorica. Las glandulas cardiacas se curvan en glandulas tubulares con la parte inferior intumescente y una pequena cavidad glandular. Las glandulas fundicas eran glandulas tubulares simples o glandulas tubulares ramificadas, donde se pueden observar con claridad las celulas principales, parietales y mucosas del cuello. Las glandulas piloricas fueron glandulas tubulares curvadas, cuanto mas cercanas a la lamina propia, mas evidente fue su forma ondulada. La tincion glucoconjugada revelo que el epitelio de la mucosa de las glandulas gastricas cardiacas, piloricas y el epitelio de las fosas gastricas secretaron principalmente un glucoconjugado neutro, pero otras porciones cardicas y de las glandulas gastricas secretaron un glucoconjugado mixto y acido, respectivamente. A la tincion de fibras reticulares, se encontro que las celulas mucosas del cuello poseian caracteristicas argirofilas. Se observo un gran numero de granulos en el citoplasma supranuclear en contraste con las celulas principales. Ademas, no fueron aislados los nodulos linfoides y presentaba tejido linfoide difuso en las glandulas de abomaso, especialmente en el cuerpo del abomaso. La tincion Gordon Sweet indico que las celulas argirofilicas se localizaron en el epitelio y lamina propia glandular, lo que tambien se observo en el tejido conectivo. Estas celulas endocrinas se dispersan individualmente en las celulas epiteliales, de vez en cuando en grupos celulares de 3-5. De esta forma, los yak pastorean durante todo el ano, en diversos pastizales naturales, y han evolucionado sus caracteristicas morfologicas que les permiten consumir una amplia variedad de especies de plantas, con lo que se adaptan mejor a las condiciones inhospitas.(AU)