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，这个问题与肺的非凡结构多样性有关，特别是导致单向气流的结构。在这方面，鸟类的肺具有特殊的地位，因为它们的设计与哺乳动物的肺有很大的不同，而且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、乌龟和变色龙，也不同于哺乳动物的肺。这项研究将更好地了解爬行动物肺部的空气动力瓣膜如何产生单向气流，这些流动模式的生理意义，以及它们在脊椎动物中的分布。它将揭示将爬行动物和两栖动物的肺结构与气流模式联系起来的基本形式-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了解；并应用于重建灭绝的四足动物的呼吸系统。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营的远程学习计划，以及开发用于研究、推广和教学的虚拟现实基础设施。(1)将对两栖动物和爬行动物肺部的气流模式进行系统分类调查。(2)将通过测量和可视化气流模式、计算流体动力学模拟和物理模型来测试下列肺空气动力瓣膜的机械基础：i)海龟有肺特斯拉瓣膜；ii)原始龙的呼气瓣功能类似于内部喷嘴，在Coanda表面诱导和放大气流；iii)呼气瓣来自尾部导流坝。(3)将气囊导管植入鳄鱼的肺部，使单向气流转化为潮汐气流。在这两种流动模式下，气动阀门的功能意义的假设将得到检验：i)鳄鱼有逆流或横流气体交换；ii)单向流动减少蒸发水和热损失的速率，并促进肺部二氧化碳的洗出和氧气的洗入。将测量每次呼吸的氧气提取和二氧化碳排出，肺洗出二氧化碳的速率，呼吸蒸发失水和热量损失的速率，以及与氧气消耗和二氧化碳排泄速率相关的通气率。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，培训实验室人员；3)通过犹他州霍格尔动物园的远程学习计划，向非专业社区推广，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NSF的法定使命，并通过使用基金会的智力优势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.