Pulmonary Aerodynamic Valves: Distribution & Function

这个项目解决了脊椎动物进化中一个主要的，鲜为人知的问题，与肺的非凡结构多样性有关，特别是产生单向气流的结构。鸟类的肺在这方面占有特殊的地位，因为它们的设计与哺乳动物的肺截然不同，而且人们一直认为单向气流与飞行的能量需求有关。然而，其他非飞行脊椎动物的肺，包括蛇、海龟和变色龙，也与哺乳动物的肺不同。这项研究将更好地理解爬行动物肺部的气动阀如何产生单向气流，这些气流模式的生理意义，以及它们在脊椎动物中的分布。它将揭示爬行动物和两栖动物肺部结构与气流模式之间的基本形式-功能关系；加强对这些气流模式对气体交换、呼吸水分损失和热量损失的影响的理解；并应用于已灭绝的四足动物呼吸系统的重建。该项目还包括重要的教育和推广活动，包括对实验室人员的科学交流培训，参与公共教育，犹他州霍格尔动物园运行的远程学习项目，以及为研究、推广和教学开发虚拟现实基础设施。拟议的研究将导致三项主要活动。将对两栖动物和爬行动物肺部的气流模式进行种系调查。(2)将通过对气流模式的测量和可视化、计算流体动力学模拟和物理模型，对以下关于肺气动阀的机制基础的假设进行检验：1)海龟有肺特斯拉阀；ii)始祖龙的呼气阀的功能就像一个内部喷嘴，其中的康达表面诱导并扩大了流量；Iii)呼气阀起源于尾端导向坝。(3)将气球导管植入短吻鳄的肺部，使单向气流转化为潮汐气流。在这两种流动状态下，将测试气动阀功能意义的假设：i)短吻鳄具有逆流或逆流气体交换；ii)单向流降低了蒸发水和热损失率，并改善了肺部二氧化碳的冲洗和氧气的冲洗。测量将包括每次呼吸时的氧气提取和二氧化碳去除、肺部二氧化碳排出率、呼吸蒸发失水和热损失率以及相对于氧气消耗和二氧化碳排泄率的通气率。拟议的研究有四个方面的教育和推广更广泛的影响：1)招募代表性不足的参与者进入STEM；2)与犹他州自然历史博物馆密切合作，培养科学传播方面的实验室人员；3)通过犹他州霍格尔动物园的远程学习项目，拓展到非专业社区，包括K-12学校；4)开发用于研究、推广和教学的虚拟现实基础设施。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project addresses a major, poorly understood question in vertebrate evolution related to the lung's extraordinary structural diversity, especially the structures that give rise to one-way airflow. Bird lungs have held a special place in this regard, because their design is so radically different from mammalian lungs, and it has been thought that one-way airflow is related to the energetic demands of flight. However, the lungs of other non-flying vertebrate animals, including snakes, turtles, and chameleons, also differ from those of mammals. This research will provide a better understanding of how aerodynamic valves in the lungs of reptiles give rise to one-way airflow, the physiological significance of these patterns of flow, and their distribution across vertebrate animals. It will reveal fundamental, form-function relationships linking lung structures to patterns of airflow in reptiles and amphibians; enhance understanding of the effects of these patterns of airflow on gas exchange, respiratory water loss, and heat loss; and be applied to reconstruction of the respiratory systems of extinct tetrapods. The project also includes significant educational and outreach activities, including science communication training for lab personnel, participation in public-education, distance-learning programs run by Utah's Hogle Zoo, and development of virtual reality infrastructure for research, outreach, and teaching.Three primary activities will result from the proposed research. (1) A phyletic survey will be made of patterns of airflow in the lungs of amphibians and reptiles. (2) Tests of the following hypotheses for the mechanistic basis of pulmonary aerodynamic valves will be made by measurements and visualizations of patterns of airflow, computational fluid dynamics simulations, and physical models: i) that turtles have a pulmonary Tesla valve; ii) that the expiratory valve of archosaurs functions like an internal nozzle, where a Coanda surface induces and amplifies flow; iii) that the expiratory valve arises from a caudal guiding dam. (3) Balloon catheters will be implanted into the lungs of alligators which will allow unidirectional flow to be converted to tidal airflow. Under these two flow regimes hypotheses for the functional significance of aerodynamic valves will be tested: i) that alligators have counter-current or cross-current gas exchange; ii) that unidirectional flow reduces rates of evaporative water and heat loss, and improves wash-out of lung CO2 and wash-in of O2. Measurements will made of O2 extraction and CO2 removal with each breath, rates of lung washout of CO2, rates of respiratory evaporative water loss and heat loss, and rates of ventilation relative to rates O2 consumption and CO2 excretion. The proposed research has four strands of educational and outreach broader impacts: 1) Recruitment of underrepresented participants into STEM; 2) Training of lab personnel in science communication, working closely with the Natural History Museum of Utah; 3) Outreach to the lay community, including K-12 schools, through distance-learning programs of Utah's Hogle Zoo; 4) Development of virtual reality infrastructure for research, outreach, and teaching.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.