鸡胚胸腺和腔上囊的组织发生

鸡胚的胸腺原基发生于第Ⅲ、Ⅳ咽囊上皮，在E4（E4指胚胎发育到第4天）到E5胸腺的上皮分化成索状，进入咽囊的间质内。从E9至E10胸腺呈长索状，环绕颈静脉分布，胸腺开始区分出皮质、髓质及大叶，E12出现胸腺小体原基。从E15至E16皮质和髓质界限明显。大约F20至E21髓质中出现典型的胸腺小体，皮质主要被中、小淋巴细胞填充。在E6到E8上囊原基泄殖背面上皮间的小空泡合并成大空泡形成。从E11到E12腔上囊出现8条－11条叶状皱襞，粘膜面出现淋巴上皮芽。大约在E16至E17初级小叶增到16条－20条，小叶内巴滤泡的髓质形成。在E18至E21滤泡髓质内的淋巴细胞向单层上皮外移动形成皮质。滤泡的粘膜面分化出吸收上皮，滤泡间者称分泌上皮。

HISTOGENESIS OF THE THYMUS AND THE FABRICIUS BURSA OF THE CHICK EMBRYOS

The thymic rudiments of the chick embryo develop from the epithelium of the 3th and 4th visceral pouches,at E 4(E 4 means embryo develop to the 4th day of incubation)to E 5 the epithelium of the thymus differentiate into cords and get in the mesenchyme of the visceral pouches.The thymus that twist around the jugular vein are elongated and begin to divide into the cortex and the medulla in the large lobes from E 9 to E 10 .The rudiments of Hassalls Corpuscles are found at E 12 .The boundary of the cortex and the medulla is obrious from E 15 to E 16 .The cortex mainly is filled by the medium and small lymphocytes,the typical Hassalls Corpuscles in the medulla appear about E 20 to E 21 . The rudiment of the Fabricius bursa develops from vacuoles between the dorsal epithelia cells of the cloaca,then small vacuoles coalescence to form a large vacuoles during E 6 to E 8 .The bursa arises eight to eleven plicaes during E 11 to E 12 and appears lymphoepihelial bud in the surface of mucosa.About E 16 to E 17 the primary lobules in the bursa have increased between sixteen to twenty,the medulla of the lymphotic follicles formed.During E 18 to E 20 the lymphocytes within follicles transfer gradully to ward out of the simple epithelium to form the cortex.The epithelium of mucosal surface of the follicles differentiates into follicular absorbed epithelium(FAE) and the epithelium between follicles are called follicuar secretive epithelium(FSE).