Martyniuk Kamila, Ziółkowska Natalia, Hanuszewska-Dominiak Maria, Szyryńska Natalia, Lewczuk Bogdan
Department of Histology and Embryology, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, 10-719 Olsztyn, Poland.
Animals (Basel). 2023 Feb 11;13(4):635. doi: 10.3390/ani13040635.
The European beaver is a herbivorous rodent whose diet changes seasonally, and in winter consists of large quantities of woody plants. It is distinguished among other mammals by a unique organization of the stomach that comprises the cardiogastric gland and by the unusual process of mucus formation in the gastric mucosa. The aim of study was to (i) characterize the structure of the beaver esophagus with particular attention to the mucosal epithelium; (ii) compare the histological structure of the esophagi collected in spring, summer, and winter; (iii) provide preliminary data on the structure of the esophagus in beaver fetuses. The study was conducted on esophagi of 18 adult beavers captured in Poland in April, August, and December, and on 3 fetal organs. The results obtained in adults show that the mucosa is lined with thick stratified squamous keratinized epithelium with a structure similar to that of the skin epidermis. Ultrastructural studies reveal the presence of multiple lamellar and non-lamellar bodies in granular cells, whose morphology and location gradually change while reaching the upper epithelial layers. The muscularis mucosa comprises a layer of longitudinally oriented bundles of smooth muscle cells. Both mucosa and submucosa do not comprise any glands. The thick muscularis externa consists mainly of internal circular and external longitudinal layers of striated muscle fibers. The keratinized layer of mucosa epithelium was 2-3-fold thicker in esophagi collected in winter than in those collected in spring and summer, while the epithelial cell layer thickness remained unchanged regardless of the season. Immunolabeling for proliferating cell nuclear antigen shows a higher index of epithelium proliferation in esophagi collected in winter than in spring and summer. No seasonal differences were noted in other layers of the esophagus. Fetal organs have epithelium covered with a keratinized layer, thinner than in adults, and the muscularis externa comprises both striated and smooth muscle cells.
欧洲河狸是一种草食性啮齿动物，其饮食会随季节变化，冬季主要以大量木本植物为食。它在其他哺乳动物中与众不同，其胃具有独特的结构，包括贲门胃腺，并且胃黏膜中黏液形成的过程也不寻常。本研究的目的是：（i）描述河狸食管的结构，特别关注黏膜上皮；（ii）比较春季、夏季和冬季采集的食管的组织学结构；（iii）提供河狸胎儿食管结构的初步数据。该研究对4月、8月和12月在波兰捕获的18只成年河狸的食管以及3个胎儿器官进行了研究。在成年河狸中获得的结果表明，黏膜内衬有厚的复层鳞状角化上皮，其结构与皮肤表皮相似。超微结构研究显示颗粒细胞中存在多个板层体和非板层体，其形态和位置在到达上皮上层时会逐渐变化。黏膜肌层由一层纵向排列的平滑肌细胞束组成。黏膜和黏膜下层均不包含任何腺体。厚的外肌层主要由横纹肌纤维的内环行层和外纵行层组成。冬季采集的食管黏膜上皮的角化层比春季和夏季采集的厚2至3倍，而上皮细胞层厚度无论季节如何均保持不变。增殖细胞核抗原的免疫标记显示，冬季采集的食管上皮增殖指数高于春季和夏季。食管其他层未未未发现季节性差异。胎儿器官的上皮覆盖有角化层，比成年河狸的薄，并且外肌层包括横纹肌和平滑肌细胞。
