苏氏(鱼芒)鲇鳔的组织学及呼吸上皮的超微结构的研究

STUDIES ON THE HISTOLOGICAL STRUCTURE OF SWIM BLADDER AND ULTRAMICROSCOPIC STRUCTURE OF RESPIRATORY-EPITHELIUM IN PANGASIUS SUTCHI

  • 摘要: 本文首次报道了苏氏(鱼芒)鲇的具有气呼吸作用的鳔的组织学和呼吸上皮的超微结构。鳔由浆膜、纤维层、粘膜上皮三层构成,纤维层的胶原纤维向鳔腔内突入衍生出密集的泡囊状小室,并在鳔腔中心汇合为中轴。泡囊小室的内表面被覆高度毛细血管化的上皮(即呼吸上皮)。呼吸上皮细胞是一类同型特化的扁平上皮细胞,电镜观察证明具有哺乳类肺泡上皮Ⅰ型和Ⅱ型细胞的结构。上皮细胞基底面与单层的毛细血管壁细胞联接形成胞质薄层的血-气屏障。研究结果证实鳔是苏氏(鱼芒)鲇的重要副呼吸器官,具有强的空气呼吸作用。

     

    Abstract: The present paper deals with the histological structure of the swimbladder and uhramicroscopic structure of mucosa (also called respiratory-epithelium) of an air-breathing catfish,Pangasius sutchi, of which the swimbladder as an obligatory respiratory organ. The structure of pneumatic duct of the fish is similar to that of the esophagus, being organized by mucosa, submucoa, muscularis and fibrosa. Formed mainly by goblet and epithelial cells, the mucosa is stratified, with longitudinal folds. Muscularis consists of well-developed circular skeletal muscle, especially in posterior part of the pneumatic duct, where the muscle is so welldeveloped that it forms a larynx-like structure to regulate the amount of air inlet and outlet of the swimbladder. The trabeculated swimbladder is composed of three parts; mucosa, collagenic fiber wall and fibrosa. The wall of swimbladder and the respiratory alveoli consist of collagenic fibers but no muscle fibers are present. The mucosa is a sort of highly vascularized respiratory epithelium with capillaries covering the luminal surface of the respiratory alveoli. Between the respiratory epithelium and collagenic fibers, there is a relatively thin layer of loose connective tissue within which fibrohlasts, various kinds of white blood corpusles and blood vessels Were found.The respiratory epithelium is a very thin cellular structure, with a layer of simple squamous epithelial cells and the endothelial cells closely connected to the basement of the epithelial cell. A rather thin basement membrane separates the epithelial cells from the endothelial cells. Hence, the blood-gas barrier for aerial exchange is composed of epithelium, basement membrane and endothelium. All the squamous epithelial cells are isotypic having T-shaped nuclei surrounded by endoplasmic reticulum and osmiophil multilamellar bodies. Mitochondria and Golgi apparatus are seen, often with vacuoles of different sizes. From the apices of the epithelium, short microvilli extend irregularly into the alveoli space. The characteristics of the epithelial cell mentioned above are similar to type Ⅰ and type Ⅱ cells of the alveolar epithelium in mammals. In this paper, the ultramicroscopic structure of endothelial cells, mast cells, and fibroblasts are also described, and the relations of the swimbladder to aerial respiration are discussed.

     

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