Crocodilian lungs are distinct from bird lungs and are thought to have a large alveolar-arterial blood gas difference, large ventilation-perfusion inhomogeneity, and parenchyma consisting of cubicles (ediculae) (3–5).
鳄鱼的肺和鸟类的肺有显著区别，肺泡动脉气血循环有差异，换气方式也不相同，并且肺实质由小隔间组成。
However,the topography of the intrapulmonary bronchus and of the first generation of bronchi is similar in birds and crocodilians (3, 6, 7).
然而，初级支气管和肺内血管的解剖结构在鸟类与鳄鱼间很相似。

Key features of the avian aerodynamic valve appear to be present in the alligator lung.
鸟类双重呼吸的关键特征也出现在了鳄鱼肺中。
The green bronchus shown in Fig. 1, the cervical ventral bronchus(CVB), is strikingly similar to the avian ventral bronchus that connects with the cervical air sacs.
图1中的绿色支气管——CVB，十分相似于鸟类连接中气囊的中支气管。



我先插一个～

The small ostium to the CVB opens into a funnel-shaped vestibule acutely angled with the intrapulmonary bronchus, so that the bronchus makes a hairpin turn ventrocranially before coursing cranially to the apex of the lung (Fig.1A, B).
CVB的小孔通向漏斗形的前庭，与肺内支气管成一定角度。以便支气管在到达肺尖之前做一个发夹形转弯。



Distalto the CVB ostium, the intrapulmonary bronchus widens and becomes partially enclosed as it curves caudally and laterally and gives rise to a pair of small medial paracardiac bronchi (Fig. 1, red bronchi),a large individual dorsolateral bronchus (Fig. 1, chartreuse Bronchus), and three caudal bronchi originating from a common terminal intrabronchial chamber (Fig. 1, blue bronchi).
在CVB小孔的末端，肺内支气管变得宽阔并部分围起，它在尾部和侧面弯曲并连接到一个心旁支气管（图1中红色）；一个巨大且独立的背侧支气管（图1中黄绿色）；还有三个来自于相同接口的气管腔的尾侧支气管（图1中蓝色）。



The anatomical similarity with the avian lung led us to hypothesize that airflow might also be unidirectional in crocodilians.
解剖结构的相似使我们猜测鳄鱼肺内的气流也是单向流动的
Previously, measurements of airflow in alligator lungs did not identify unidirectional flow (8).
在此之前，对于鳄鱼肺内气流的测量并没有检测出单向流动。
Perry discussed the possibility that crocodilians have unidirectional airflow, but concluded that airflow is tidal in crocodilians and that unidirectional flow evolved in coelurosaurian-grade dinosaurs (9–12).
佩里讨论过鳄鱼具有单向流动的可能性，但是认为鳄鱼是潮式呼吸,而虚骨类恐龙才有双重呼吸。
Furthermore, for avian-style respiration to occur in birds and nonavian dinosaurs, abdominal air sacs have been presumed to be critical (13), and the hepatic piston mechanism of ventilation of crocodilians has been presumed incompatible (14).
此外，腹气囊被认为是鸟类呼吸方式的关键，这与鳄鱼呼吸用的肝活塞矛盾。（注：鳄鱼用肝瓣拉动肺呼吸，类似哺乳类的隔膜）

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We also visualized flow by filling an excised lung with saline containing fluorescent microspheres.
我们还通过对离体肺充入含荧光微球的溶液进行了直观观察。
In the CVB, the microspheres flowed in a cranial-to-caudal direction as the fluid was pushed into and pulled out of the lung (movies S1
and S2).
在CVB中，无论在溶液注入还是排出时，荧光微球标记都显示为从头至尾流动(电影 S1 和 S2).
In the parabronchi, the spheres also flowed unidirectionally (movie S3).
在副支气管中，球体也是单向流动的。（电影S3）
All three methods—in vivo recordings of airflow, recordings of airflow in
artificially ventilated excised lungs, and visualization of water flow in artificially ventilated lungs—indicate that fluid flows unidirectionally through the
lungs of alligators in a strikingly birdlike pattern.
以上三种实验，离体肺的记录，活体肺的记录，充入微球的记录，都明确的显示鳄鱼肺的气流方式与鸟类相同。

学生物 学英文?

最近怎么老看到双重呼吸讲解。。

During exhalation, the configuration of the later obronchial ostia may cause air to move dorsally to enter the ostia of the dorsobronchi,rather than leaving the lung directly by way of the mesobronchus (1).
在呼气时，后方支气管小孔的构造使空气进入背支气管，而不是从两侧支气管直接离开肺。
During inspiration, rapid flow of air along the intrapulmonary bronchus past the ostia to the ventrobronchi may reduce lateral pressure at this location because of the Venturi effect, and the low pressure may act as a suction pump to draw air past the mouths of the ventrobronchi into the mesobronchus (1).
在吸气时，快速的气流沿着肺内支气管通过ventrobronchi的小孔由于文丘里效应降低了气压。低压像一个抽气机使空气从ventrobronchi流向了中支气管。
A glassmodel demonstrated how this geometry gives rise to unidirectional airflow (1).
一个玻璃模型能演示这种几何结构是如何产生单向流动的。

厉害！

Also,the mechanism of gas exchange in crocodilians is not known; a crosscurrent
mechanism has been hypothesized(11), but a countercurrent mechanism cannot be ruled out.
鳄鱼的具体气体交换机制还不明朗，有一种相反的猜测，这种猜测还不能被排除
Furthermore,the importance of unidirectional airflow for gas exchange efficiency in the alligator lung is not known and cannot be determined from our data, which
consist of measurements of airflow.
此外，鳄鱼肺单向流动是否提高了气体交换效率这一重点尚不可知，还没从我们的的实验中得出。

再插一下～