Department of Zoology, Faculty of Science, Sohag University, Sohâg, 82524, Egypt.
J Mol Histol. 2022 Apr;53(2):449-472. doi: 10.1007/s10735-022-10071-z. Epub 2022 Mar 6.
The microanatomical features of the intestinal tract mucosa layer in different species of tetrapoda vary according to the type of species, tissue, and function of the targeted cells. In the present study, we have evaluated the histological and histochemical variations of the intestinal tract in four species representing superclass tetrapoda. Bufo regularis (toad), Trachylepis quinquetaeniata (lizard), Columba livia domestica (pigeon) and Mus musculus (mouse) were used as representatives for amphibians, reptilians, avians and mammalians respectively. Histologically, the ileum's mucosal layer of the lower tetrapods (toad and lizard) was almost similar and consists of elongated finger-like shape villi lined with simple columnar epithelium and goblet cells. Similarly, the microanatomical features in ileum of higher tetrapod representatives (pigeon and mouse) were characterized by the presence of villi lined with simple columnar epithelium and scattered goblet cells as well as intestinal glands (crypts of Lieberkühn) at the bases of the intestinal villi. In the toad rectum, the mucosal layer was similar to that of the ileum but with shorter villi and more numerous goblet cells. However, the mucosal layer of the rectum in the lizard had low numbers of absorptive columnar epithelial cells with abundant goblet basal cells. Comparatively, the pigeon's rectal mucosa had almost a similar structure to that of ileum but in leaf-like shaped villi. Finally, the rectum of the mouse has narrow rectal pits, instead of villi, lined with goblet cells and absorptive epithelial cells. Histochemically, the ileum in the four studied tetrapod representatives showed varying biodistribution profiles of neutral, sulfated and carboxylated mucins. There are variations encountered in the intestinal brush border and goblet cells of villi in all species as well as the crypts of Lieberkühn in higher tetrapods. Also, the rectum of all tetrapod species showed weak to strong positive signals for the three types of mucins in the brush border and goblet cells of villi in all species and crypts of Lieberkühn in higher tetrapods as well. In addition, the brush border of toad's rectum was lacking sulfated mucins and that of the lizard did not have any type of mucins. The data of this study will contribute to understand the relationship between the microanatomical features and mucins biodistribution profiles in the mucosal layer of tetrapod intestinal tract and their functions.
不同四足动物肠道黏膜层的微观解剖特征因物种类型、组织和靶向细胞的功能而异。在本研究中，我们评估了代表超纲四足动物的四个物种的肠道组织学和组织化学变化。我们使用中华蟾蜍（蛙）、五线石龙子（蜥蜴）、原鸽（鸽）和小家鼠（鼠）分别作为两栖动物、爬行动物、鸟类和哺乳动物的代表。组织学上，低等四足动物（蛙和蜥蜴）回肠的黏膜层几乎相似，由长而指状的绒毛组成，衬有单层柱状上皮和杯状细胞。同样，高等四足动物代表（鸽和鼠）回肠的微观解剖特征表现为绒毛衬有单层柱状上皮和散在的杯状细胞以及在绒毛基部的肠腺（李氏隐窝）。在蟾蜍的直肠中，黏膜层与回肠相似，但绒毛较短，杯状细胞较多。然而，蜥蜴的直肠黏膜层具有较少的吸收柱状上皮细胞，而具有丰富的杯状基底细胞。相比之下，鸽的直肠黏膜具有与回肠几乎相似的结构，但呈叶状绒毛。最后，鼠的直肠具有狭窄的直肠隐窝，而不是绒毛，由杯状细胞和吸收上皮细胞衬里。组织化学上，在研究的四个四足动物代表的回肠中，中性、硫酸化和羧化粘蛋白表现出不同的生物分布谱。在所有物种的绒毛和肠隐窝的肠刷状缘和杯状细胞中以及高等四足动物的肠隐窝中都遇到了变化。此外，所有四足动物的直肠在绒毛和杯状细胞的肠刷状缘以及高等四足动物的肠隐窝中都显示出三种类型粘蛋白的弱至强阳性信号。此外，蟾蜍直肠的刷状缘缺乏硫酸化粘蛋白，蜥蜴的刷状缘没有任何类型的粘蛋白。本研究的数据将有助于了解四足动物肠道黏膜层的微观解剖特征与粘蛋白生物分布谱及其功能之间的关系。
