牦牛肺脏的适应性结构

应用光镜和电镜技术，对牦牛肺脏的微细结构进行了系统观测，分析其结构特性与高原低氧环境适应性的关系。结果表明，牦牛肺小叶结构明显，肺泡I型上皮菲薄，构成肺泡壁的绝大部分。与其它动物不同，牦牛I型肺泡上皮见有间断处，为非连续型上皮。气－血屏障的算术平均厚度和调和平均厚度分别为0.53±0.10µm和0.44±0.07µm，明显比体格较小的其它家畜还要薄，这有利于气体交换时增加氧的弥散量。肺脏微动脉中膜的肌层厚度与血管外径的百分比为5.00±0.93%，与高原驼马的比值近似，而比奶牛和公牛的要小，可减少牦牛肺动脉高压的发病几率。肺胸膜、小叶间隔、肺泡隔、各级支气管管壁和血管壁内都有丰富的弹性纤维分布，并相互联系，构成一个完整的弹性系统，维持肺脏良好的扩张和回缩状态。杯状细胞不仅大量分布于各级支气管，细支气管粘膜上皮中也出现杯状细胞，其分泌的粘液有助于牦牛在干旱环境下保护呼吸道的通气量。这些结构特点是牦牛世代生活于高原低氧环境下所获得的适应性变化。

Structural Study on Plateau Adaptability of Yak Lung

Fine structure of the yak lung was examined by microscopy and trans electro-microscopy, and then, the relationship between the morphological features and the adaptability to lower-oxygen was analyzed. The lobuli pulmonum occurred obviously. Most of the alveoli wall composed by type I alveolar cells which had gaps on it clearly. The arithmetic and conciliate averages of the air-blood barrier thickness were 0.53±0.10µm and 0.44±0.07µm respectively, which were notabilitly smaller than that of other smaller livestock. Those can facilitate the dispersion of oxygen through the barrier. The rate of muscle-layer thickness to outer diameter of the blood vessel was 5.00±0.93%, being similar as the camel house but smaller than the cow and bull, which can reduce pulmonary artery high pressure. There were lots of elastic fibres in pulmonary pleura, interlobular connective tissue, alveolar septa, the walls of different bronchus and blood vessels， which formed a complete elastic system in favor of the lung dilating and shrinking. Goblet cells that distributed not only in different bronchi but also in bronchioles, were good for dry air passing through the tract. These structural features were obtained by yaks as a result of their living in lower-oxygen on Qingzang Plateau from generation to generation.