Woodward Jeremy D, Maina John N
School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
J Anat. 2005 May;206(5):477-92. doi: 10.1111/j.1469-7580.2005.00413.x.
To elucidate the shape, size, and spatial arrangement and association of the terminal respiratory units of the avian lung, a three-dimensional (3D) computer-aided voxel reconstruction was generated from serial plastic sections of the lung of the adult muscovy duck, Cairina moschata. The air capillaries (ACs) are rather rotund structures that interconnect via short, narrow passageways, and the blood capillaries (BCs) comprise proliferative segments of rather uniform dimensions. The ACs and BCs anastomose profusely and closely intertwine with each other, forming a complex network. The two sets of respiratory units are, however, absolutely not mirror images of each other, as has been claimed by some investigators. Historically, the terms 'air capillaries' and 'blood capillaries' were derived from observations that the exchange tissue of the avian lung mainly consisted of a network of minuscule air- and vascular units. The entrenched notion that the ACs are straight (non-branching), blind-ending tubules that project outwards from the parabronchial lumen and that the BCs are direct tubules that run inwards parallel to and in contact with the ACs is overly simplistic, misleading and incorrect. The exact architectural properties of the respiratory units of the avian lung need to be documented and applied in formulating reliable physiological models. A few ostensibly isolated ACs were identified. The mechanism through which such units form and their functional significance, if any, are currently unclear.
为阐明禽肺终末呼吸单位的形状、大小、空间排列及关联，利用成年番鸭（Cairina moschata）肺的系列塑料切片构建了三维（3D）计算机辅助体素重建模型。气毛细血管（ACs）是相当圆润的结构，通过短而窄的通道相互连接，血毛细血管（BCs）由尺寸相当均匀的增殖段组成。ACs和BCs大量吻合且彼此紧密缠绕，形成一个复杂的网络。然而，正如一些研究者所声称的，这两组呼吸单位绝不是彼此的镜像。从历史上看，“气毛细血管”和“血毛细血管”这两个术语源于这样的观察结果：禽肺的交换组织主要由微小的空气和血管单位网络组成。那种根深蒂固的观念，即ACs是从副支气管腔向外伸出的直的（无分支）、盲端小管，而BCs是与ACs平行向内延伸并与之接触的直接小管，过于简单化、具有误导性且不正确。禽肺呼吸单位的确切结构特性需要记录下来，并应用于构建可靠的生理模型。发现了一些表面上孤立的ACs。目前尚不清楚这些单位形成的机制及其功能意义（如果有的话）。
