单环刺螠虫消化道组织学和细胞学

Histology and cytology of digestive tract in Urechis unicoinctus VonDrasche

对单环刺虫(UrechisunicoinctusVonDrasche)消化道的结构进行了组织学和细胞学观察。单环刺虫消化道可分为咽、食道、嗉囊、砂囊、胃、中肠、呼吸肠、直肠和排泄腔。咽、食道和直肠管壁由内向外分为粘膜层、粘膜下层、肌层和外膜,嗉囊、砂囊、胃、中肠和呼吸肠壁仅由粘膜层和外膜组成。除食道外,胃之前的消化道及直肠上皮细胞均有发达的纤毛,中肠和呼吸肠上皮主要为微绒毛。消化道上皮主要分为3类细胞,第1种为柱状上皮细胞;第2种为粘液细胞;第3种为分泌细胞。粘液细胞和分泌细胞散布于柱状上皮细胞之间,且结构和数量随部位而异:粘液细胞在咽、食道、嗉囊、胃、中肠和直肠上皮中有较多的分布,分泌细胞在砂囊、胃、中肠和呼吸肠中数量较多。

The structure of digestive tract was observed with light microscope and electron microscope in Urechis unicoinctus VonDrasche. The digestive tract can be divided into pharynx, esophagus, craw, gizzad, stomach, mid-gut, aspiratory intestines, rectum, and cloacae. The walls of pharynx, esophagus and rectum are composed of mucosa, submucosa, muscularis and adventitia. The muscularis and submucosa are absent in craw, gizzard, stomach, mid-gut and aspiratory intestines. Ahead of the stomach the epithelium is almost composed of ciliated and mucus cells with developed microvilli and mucus cells except the esophagus. In the midgut and aspiratory intestines, the epithelium is composed of microvillate and secretory cells. Three kinds of cells are distinguished in the epithelia of digestive tract that one kind is mainly column epithelia, and the second is mucous cell and the third is decretory cell. The last two kinds of cells intersperse among the epithelia, and the quantity is different at different parts. The mucous cells are much more distributed in pharynx, esophagus, craw, stomach and rectum than in the other sections while the secretory cells are more in gizzard, stomach, midgut and aspiratory intestines. 