KS3 Science: Respiration and Gas Exchange — KS3 科学：呼吸与气体交换

一、什么是呼吸？从细胞层面理解 | What is Respiration? Understanding It at the Cellular Level

呼吸（respiration）是生物体将食物中的化学能转化为可用能量的过程。许多同学一开始会混淆”呼吸”（breathing）和”细胞呼吸”（cellular respiration）这两个概念 – breathing 是指空气进出肺部的物理动作，而 respiration 则是在细胞内发生的化学反应，将葡萄糖与氧气结合，释放出 ATP（三磷酸腺苷），这是细胞能够直接使用的能量货币。在 KS3 科学课程中，理解这一区别是整个呼吸主题的起点。

Respiration is the process by which living organisms convert chemical energy stored in food into usable energy. Many students initially confuse “breathing” with “cellular respiration” – breathing refers to the physical movement of air in and out of the lungs, whereas respiration is a chemical reaction that takes place inside cells, combining glucose with oxygen to release ATP (adenosine triphosphate), the energy currency that cells can use directly. In the KS3 Science curriculum, understanding this distinction is the starting point for the entire respiration topic.

呼吸作用发生的场所是细胞内的线粒体（mitochondria）。线粒体被称为”细胞的发电站”，因为它们负责将葡萄糖分子分解，释放出其中储存的能量。每一个活细胞都需要能量来维持生命活动 – 无论是肌肉收缩、神经信号传递，还是细胞分裂和生长，都离不开呼吸作用产生的 ATP。

Respiration takes place inside the mitochondria, which are organelles found within cells. Mitochondria are often called the “powerhouses of the cell” because they are responsible for breaking down glucose molecules and releasing the energy stored within them. Every living cell requires energy to sustain life processes – whether it is muscle contraction, nerve signal transmission, or cell division and growth, none of these can happen without the ATP produced by respiration.

二、呼吸系统的组成器官及其功能 | Organs of the Respiratory System and Their Functions

人体呼吸系统由一系列专门器官组成，它们协同工作，将空气中的氧气输送到血液中，并将二氧化碳排出体外。呼吸系统的主要器官包括：鼻腔（nasal cavity）、咽部（pharynx）、喉部（larynx）、气管（trachea）、支气管（bronchi）、细支气管（bronchioles）和肺泡（alveoli）。

The human respiratory system consists of a series of specialised organs that work together to deliver oxygen from the air into the bloodstream and expel carbon dioxide from the body. The main organs of the respiratory system include: the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli.

空气首先通过鼻腔或口腔进入体内。鼻腔内部的黏膜和纤毛（cilia）可以过滤空气中的灰尘和微生物，同时温暖和湿润吸入的空气。接着空气经过咽部和喉部 – 喉部还包含声带，使我们能够发声。然后空气进入气管，这是一条由 C 形软骨环支撑的管道，确保气管始终保持打开状态。气管向下分支成两根支气管，分别进入左右两肺。支气管在肺内继续分支，形成越来越细的细支气管，最终通向数百万个微小的气囊 – 肺泡。

Air first enters the body through the nasal cavity or mouth. The mucous membrane and cilia inside the nasal cavity filter dust and microorganisms from the air, while also warming and moistening the inhaled air. The air then passes through the pharynx and larynx – the larynx also contains the vocal cords, enabling us to produce sound. Next, air enters the trachea, a tube supported by C-shaped rings of cartilage that ensure the airway remains open at all times. The trachea branches downwards into two bronchi, each leading into one of the two lungs. Inside the lungs, the bronchi continue to divide into increasingly narrower bronchioles, eventually reaching millions of tiny air sacs called alveoli.

膈肌（diaphragm）和肋间肌（intercostal muscles）是驱动呼吸运动的关键肌肉。膈肌是一层位于胸腔底部的穹顶状肌肉，当它收缩时向下移动，增大胸腔容积；肋间肌位于肋骨之间，收缩时将肋骨向上和向外拉动。这两组肌肉的协调运动产生了吸气和呼气。

The diaphragm and intercostal muscles are the key muscles that drive the breathing movements. The diaphragm is a dome-shaped sheet of muscle located at the base of the chest cavity; when it contracts, it moves downwards, increasing the volume of the chest cavity. The intercostal muscles are located between the ribs and, when they contract, pull the ribs upwards and outwards. The coordinated movement of these two sets of muscles produces inhalation and exhalation.

三、肺泡内的气体交换机制 | The Mechanism of Gas Exchange in the Alveoli

气体交换（gas exchange）是呼吸系统最核心的功能，发生在肺泡与毛细血管之间。肺泡是呼吸树末端的微小气囊，每个肺泡的壁极薄 – 仅有一个细胞的厚度 – 并且被密集的毛细血管网络所包裹。这种结构特点使得氧气和二氧化碳能够通过扩散（diffusion）快速地在空气和血液之间进行交换。

Gas exchange is the most essential function of the respiratory system and occurs between the alveoli and the surrounding capillaries. Alveoli are tiny air sacs at the ends of the respiratory tree; each alveolus has an extremely thin wall – only one cell thick – and is wrapped in a dense network of capillaries. These structural features allow oxygen and carbon dioxide to be exchanged rapidly between the air and the blood through the process of diffusion.

扩散是指粒子从高浓度区域向低浓度区域净移动的过程，不需要消耗额外能量（因此称为被动运输）。在吸气后，肺泡内的氧气浓度高于流经肺泡的血液中的氧气浓度，因此氧气从肺泡扩散进入血液。与此同时，血液中二氧化碳的浓度高于肺泡内空气的二氧化碳浓度，因此二氧化碳从血液扩散进入肺泡，在呼气时被排出体外。

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration, requiring no additional energy (hence it is classified as passive transport). After inhalation, the concentration of oxygen inside the alveoli is higher than the concentration of oxygen in the blood flowing past the alveoli, so oxygen diffuses from the alveoli into the blood. At the same time, the concentration of carbon dioxide in the blood is higher than the concentration of carbon dioxide in the alveolar air, so carbon dioxide diffuses from the blood into the alveoli and is expelled during exhalation.

肺泡具有多种适应性特征来最大化气体交换效率：它们数量庞大（成人约有 3 亿个肺泡），提供了巨大的表面积；壁极薄，缩短了扩散距离；表面湿润，有助于气体溶解；并且被丰富的毛细血管网络紧密包裹，维持了持续的浓度梯度，确保扩散不断进行。

Alveoli possess several adaptive features that maximise the efficiency of gas exchange: they are extremely numerous (an adult has approximately 300 million alveoli), providing an enormous total surface area; their walls are extremely thin, minimising the diffusion distance; their surfaces are moist, which helps gases dissolve; and they are tightly wrapped in a rich network of capillaries, maintaining a steep concentration gradient that ensures continuous diffusion.

四、吸气和呼气的机械过程 | The Mechanical Process of Inhalation and Exhalation

呼吸运动（ventilation）包括吸气（inhalation）和呼气（exhalation）两个阶段，由膈肌和肋间肌的协调收缩与放松来驱动。这是一个物理过程，与气体交换（化学过程）不同，但它为气体交换创造了必要的条件 – 不断更新肺泡内的空气，维持氧气和二氧化碳的浓度梯度。

Ventilation consists of two phases – inhalation and exhalation – driven by the coordinated contraction and relaxation of the diaphragm and intercostal muscles. This is a physical process, distinct from gas exchange (which is chemical), but it creates the necessary conditions for gas exchange by continuously refreshing the air inside the alveoli and maintaining the concentration gradients of oxygen and carbon dioxide.

在吸气过程中，膈肌收缩并向下移动（变平），同时外肋间肌收缩，将肋骨向上和向外拉动。这两个动作共同导致胸腔容积增大，肺内气压因此降至低于大气压的水平。由于空气总是从高压区流向低压区，外部空气被吸入肺部。在进行深呼吸时，颈部和胸部的辅助肌肉也会参与，进一步增加胸腔容积。

During inhalation, the diaphragm contracts and moves downwards (flattening), while the external intercostal muscles contract, pulling the ribs upwards and outwards. Together, these two actions increase the volume of the chest cavity, causing the air pressure inside the lungs to drop below atmospheric pressure. Since air always flows from areas of high pressure to areas of low pressure, external air is drawn into the lungs. During deep breathing, accessory muscles in the neck and chest also become involved, further expanding the chest cavity.

呼气通常是一个被动过程：膈肌和外肋间肌放松，膈肌恢复其穹顶形状向上回弹，肋骨在重力作用下向下回落。胸腔容积减小，肺内气压升高至高于大气压，空气被推出肺部。在用力呼气（如咳嗽或吹气球）时，内肋间肌和腹部肌肉会主动收缩，加速空气排出。

Exhalation is usually a passive process: the diaphragm and external intercostal muscles relax; the diaphragm returns to its dome shape and moves back upwards, and the ribs fall back downwards under gravity. The volume of the chest cavity decreases, raising the air pressure inside the lungs above atmospheric pressure, and air is pushed out of the lungs. During forced exhalation (such as coughing or blowing up a balloon), the internal intercostal muscles and abdominal muscles contract actively to accelerate the expulsion of air.

五、有氧呼吸的化学反应与能量释放 | The Chemical Reaction of Aerobic Respiration and Energy Release

有氧呼吸（aerobic respiration）是在氧气充足的情况下发生的主要呼吸形式。它的总反应方程式可以用以下文字公式和化学方程式表示：

Aerobic respiration is the primary form of respiration that occurs when adequate oxygen is available. Its overall reaction can be represented by the following word equation and chemical equation:

文字公式： 葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）

Word equation: glucose + oxygen → carbon dioxide + water (+ energy)

化学方程式： C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ ATP)

Chemical equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ ATP)

有氧呼吸是需氧生物获取能量的最有效方式。每分子葡萄糖通过有氧呼吸可以产生约 36-38 个 ATP 分子。这个过程实际上分为几个阶段 – 糖酵解（发生在细胞质中）、克雷布斯循环和电子传递链（均发生在线粒体内）。在 KS3 阶段，同学们不需要记忆这些中间步骤的细节，但需要知道反应物（葡萄糖和氧气）和产物（二氧化碳、水和能量），并理解这是一个放热反应（exothermic reaction），因为反应过程中向周围环境释放了能量。

Aerobic respiration is the most efficient way for aerobic organisms to obtain energy. Each glucose molecule can yield approximately 36-38 ATP molecules through aerobic respiration. The process is actually divided into several stages – glycolysis (occurring in the cytoplasm), the Krebs cycle, and the electron transport chain (both occurring inside the mitochondria). At the KS3 level, students are not required to memorise the details of these intermediate steps but need to know the reactants (glucose and oxygen) and products (carbon dioxide, water, and energy), and understand that this is an exothermic reaction because energy is released to the surroundings during the process.

六、无氧呼吸：当氧气不足时发生了什么 | Anaerobic Respiration: What Happens When Oxygen Is Insufficient

当剧烈运动导致肌肉细胞无法获得足够的氧气时，细胞会转而进行无氧呼吸（anaerobic respiration）。这种呼吸形式不需要氧气，但效率远低于有氧呼吸 – 每分子葡萄糖仅能产生 2 个 ATP 分子。无氧呼吸在人体内的反应可以概括为：

When intense exercise prevents muscle cells from receiving sufficient oxygen, cells switch to anaerobic respiration. This form of respiration does not require oxygen but is far less efficient than aerobic respiration – it produces only 2 ATP molecules per glucose molecule. The reaction for anaerobic respiration in humans can be summarised as:

文字公式： 葡萄糖 → 乳酸（+ 少量能量）

Word equation: glucose → lactic acid (+ a small amount of energy)

乳酸的积累是导致运动后肌肉酸痛和疲劳的主要原因。当肌肉中的乳酸浓度升高时，肌肉的 pH 值下降，酶活性受到抑制，肌肉收缩能力减弱。这就是为什么进行高强度短跑或举重后，肌肉会感到灼烧感和无力。好消息是，运动停止后，乳酸会被血液运送至肝脏，在那里被转化回葡萄糖或进一步分解 – 这个过程需要额外的氧气，这部分额外需要的氧气被称为”氧债”（oxygen debt）。

The accumulation of lactic acid is the main cause of muscle soreness and fatigue after exercise. When the concentration of lactic acid in muscles rises, the pH of the muscle tissue drops, enzyme activity is inhibited, and the ability of muscles to contract is reduced. This is why muscles feel a burning sensation and weakness after high-intensity sprinting or weightlifting. The good news is that once exercise stops, lactic acid is transported by the blood to the liver, where it is converted back into glucose or broken down further – this process requires additional oxygen, and the extra oxygen required is referred to as the “oxygen debt.”

不同生物的无氧呼吸产物也不同。例如，酵母菌（yeast）在无氧条件下进行发酵，将葡萄糖转化为乙醇和二氧化碳，这一过程被广泛用于酿造啤酒和烘焙面包：

Different organisms produce different end products from anaerobic respiration. For example, yeast carries out fermentation under anaerobic conditions, converting glucose into ethanol and carbon dioxide – a process widely used in brewing beer and baking bread:

酵母发酵： 葡萄糖 → 乙醇 + 二氧化碳（+ 少量能量）

Yeast fermentation: glucose → ethanol + carbon dioxide (+ a small amount of energy)

七、有氧呼吸与无氧呼吸的系统对比 | Systematic Comparison of Aerobic and Anaerobic Respiration

理解有氧呼吸和无氧呼吸之间的差异是 KS3 考试中的高频考点。两者都是将葡萄糖转化为可用能量的过程，但在条件、效率和产物上存在本质区别。以下从六个维度进行系统对比：

Understanding the differences between aerobic and anaerobic respiration is a frequently tested topic in KS3 examinations. Both are processes that convert glucose into usable energy, but they differ fundamentally in their conditions, efficiency, and products. The following is a systematic comparison across six dimensions:

1. 是否需要氧气：有氧呼吸需要氧气；无氧呼吸不需要氧气。

1. Oxygen requirement: Aerobic respiration requires oxygen; anaerobic respiration does not.

2. 发生场所：有氧呼吸大部分在线粒体内完成；无氧呼吸则完全发生在细胞质中。

2. Location: Most of aerobic respiration takes place inside the mitochondria; anaerobic respiration occurs entirely in the cytoplasm.

3. ATP 产量：有氧呼吸每分子葡萄糖产生约 36-38 个 ATP；无氧呼吸每分子葡萄糖仅产生 2 个 ATP。

3. ATP yield: Aerobic respiration produces approximately 36-38 ATP per glucose molecule; anaerobic respiration produces only 2 ATP per glucose molecule.

4. 最终产物：有氧呼吸产生二氧化碳和水（均为无毒产物）；人体无氧呼吸产生乳酸（有毒，会引起肌肉疲劳），酵母无氧呼吸产生乙醇和二氧化碳。

4. End products: Aerobic respiration produces carbon dioxide and water (both non-toxic); anaerobic respiration in humans produces lactic acid (toxic, causes muscle fatigue), and in yeast produces ethanol and carbon dioxide.

5. 反应完全程度：有氧呼吸将葡萄糖完全氧化分解；无氧呼吸仅将葡萄糖部分分解，乳酸分子中仍含有大量未释放的化学能。

5. Completeness of breakdown: Aerobic respiration completely oxidises glucose; anaerobic respiration only partially breaks down glucose, and the lactic acid molecules still contain a significant amount of unreleased chemical energy.

6. 持续时间：有氧呼吸可以持续进行，只要氧气和葡萄糖供应充足；无氧呼吸仅能维持较短时间（通常几十秒到几分钟），因为乳酸的积累最终会抑制肌肉功能。

6. Duration: Aerobic respiration can continue indefinitely as long as oxygen and glucose supplies are adequate; anaerobic respiration can only be sustained for a short period (typically tens of seconds to a few minutes) because the accumulation of lactic acid eventually impairs muscle function.

八、植物中的呼吸作用 | Respiration in Plants

植物和动物一样，每时每刻都在进行呼吸作用，将葡萄糖分解以释放能量来驱动各项生命活动 – 包括主动运输（active transport）、细胞分裂、蛋白质合成和生长。一个常见的误解是认为植物只进行光合作用而不进行呼吸，或者认为植物只在夜间进行呼吸。实际上，植物的呼吸作用是持续不断的，无论白天还是黑夜。

Like animals, plants carry out respiration continuously, breaking down glucose to release energy that drives various life processes – including active transport, cell division, protein synthesis, and growth. A common misconception is that plants only perform photosynthesis and do not respire, or that plants only respire at night. In reality, plant respiration is continuous, occurring both day and night.

然而，植物在白天同时进行光合作用和呼吸作用，情况比动物更为复杂。光合作用吸收二氧化碳并释放氧气，而呼吸作用消耗氧气并释放二氧化碳。在白天，光合作用的速率通常高于呼吸作用速率，因此植物净吸收二氧化碳，净释放氧气。到了夜晚，光合作用因缺少光照而停止，但呼吸作用继续进行，此时植物净吸收氧气，净释放二氧化碳。

However, during the daytime, plants carry out both photosynthesis and respiration simultaneously, making the situation more complex than in animals. Photosynthesis takes in carbon dioxide and releases oxygen, while respiration consumes oxygen and releases carbon dioxide. During the day, the rate of photosynthesis is usually higher than the rate of respiration, so plants have a net uptake of carbon dioxide and a net release of oxygen. At night, photosynthesis ceases due to the absence of light, but respiration continues – at this point, plants have a net uptake of oxygen and a net release of carbon dioxide.

这也是为什么在医院病房中通常不在夜间摆放大量植物的原因 – 它们会与病人竞争有限的氧气。同样地，在卧室中放置过多植物也可能在夜间略微降低室内氧气水平。不过需要指出的是，几盆室内植物对室内氧气水平的影响微乎其微，远低于一个人在房间内呼吸所消耗的氧气量。

This is also why hospital wards typically do not keep large numbers of plants at night – they would compete with patients for the limited oxygen. Similarly, having too many plants in a bedroom may slightly reduce the indoor oxygen level at night. It is worth noting, however, that a few houseplants have a negligible effect on indoor oxygen levels, far less than the oxygen consumed by a single person breathing in the room.

九、运动对呼吸的影响及实验探究 | The Effect of Exercise on Respiration and Experimental Investigation

运动对呼吸速率和深度有显著影响。当开始运动时，肌肉收缩需要更多的 ATP，因此呼吸速率加快以提供更多的氧气并清除产生的二氧化碳。这一变化可以通过简单的实验来测量和记录 – 这是 KS3 科学中的常见实践活动。

Exercise has a significant effect on breathing rate and depth. When exercise begins, muscle contraction requires more ATP, so the breathing rate increases to deliver more oxygen and remove the carbon dioxide produced. This change can be measured and recorded through simple experiments – a common practical activity in KS3 Science.

实验方法：测量静息状态下的呼吸速率（通过计算 30 秒内胸部的起伏次数，然后乘以 2 得到每分钟的呼吸次数）。然后进行一定量的运动（如原地跑步或上下台阶 2 分钟），运动结束后立即再次测量呼吸速率，之后每隔 1 分钟测量一次，直到呼吸速率恢复到静息水平。将数据记录在表格中，并绘制呼吸速率随时间变化的折线图。

Experimental method: Measure the resting breathing rate by counting the number of chest rises in 30 seconds, then multiply by 2 to obtain the breaths per minute. Next, perform a set amount of exercise (such as running on the spot or stepping up and down for 2 minutes), then measure the breathing rate again immediately after exercise, and continue measuring every minute thereafter until the breathing rate returns to the resting level. Record the data in a table and plot a line graph of breathing rate against time.

预期结果：呼吸速率在运动结束时达到峰值，然后随着恢复时间的推移逐渐下降。通常情况下，静息呼吸速率约为 12-16 次/分钟；中等强度运动后可能升高至 30-40 次/分钟；高强度运动后甚至可能超过 50 次/分钟。恢复至静息水平所需的时间取决于个体的健康水平 – 体能越好的人，恢复得越快。

Expected results: Breathing rate peaks at the end of exercise and then gradually declines as recovery time progresses. Typically, resting breathing rate is around 12-16 breaths per minute; after moderate exercise it may rise to 30-40 breaths per minute; after high-intensity exercise it may exceed 50 breaths per minute. The time taken to return to resting level depends on the fitness level of the individual – the fitter a person is, the faster the recovery.

除了呼吸速率，心率也会在运动期间同步增加，以便更快地将氧气输送到肌肉并将二氧化碳运回肺部。这两个系统的协调反应展示了人体内器官系统之间精密的协作关系。

In addition to breathing rate, heart rate also increases in sync during exercise to deliver oxygen to the muscles more quickly and transport carbon dioxide back to the lungs. The coordinated response of these two systems demonstrates the intricate collaboration between organ systems within the human body.

十、呼吸系统的健康与疾病防护 | Respiratory System Health and Disease Prevention

保持呼吸系统健康对于维持正常的呼吸功能至关重要。影响呼吸系统健康的主要因素包括：吸烟（包括二手烟）、空气污染、呼吸道感染以及职业性粉尘暴露。吸烟是导致慢性阻塞性肺疾病（COPD）、肺气肿和肺癌的最主要风险因素 – 香烟烟雾中的焦油会破坏纤毛，使肺部失去自我清洁能力；尼古丁会使气道收缩；一氧化碳会与血红蛋白结合，降低血液的携氧能力。

Maintaining respiratory system health is essential for sustaining normal respiratory function. The main factors affecting respiratory system health include: smoking (including second-hand smoke), air pollution, respiratory infections, and occupational dust exposure. Smoking is the leading risk factor for chronic obstructive pulmonary disease (COPD), emphysema, and lung cancer – tar in cigarette smoke damages the cilia, depriving the lungs of their self-cleaning ability; nicotine constricts the airways; and carbon monoxide binds to haemoglobin, reducing the oxygen-carrying capacity of the blood.

哮喘（asthma）是另一种常见的呼吸系统疾病，表现为气道的慢性炎症和可逆性狭窄。哮喘患者在接触触发因素（如花粉、尘螨、冷空气或运动）时，会出现喘息、胸闷、咳嗽和呼吸困难等症状。哮喘可以通过避免触发因素和使用吸入性药物（如支气管扩张剂）来管理。

Asthma is another common respiratory condition, characterised by chronic inflammation and reversible narrowing of the airways. When exposed to triggers (such as pollen, dust mites, cold air, or exercise), asthma sufferers may experience wheezing, chest tightness, coughing, and shortness of breath. Asthma can be managed by avoiding triggers and using inhaled medications (such as bronchodilators).

预防呼吸系统疾病的有效措施包括：不吸烟并避免二手烟暴露；在空气污染严重时佩戴口罩；定期进行有氧运动以增强肺活量；保持良好的室内通风；以及通过均衡饮食摄取足够的抗氧化剂（如维生素 C 和维生素 E），这些物质有助于保护肺组织免受氧化损伤。

Effective measures for preventing respiratory diseases include: not smoking and avoiding exposure to second-hand smoke; wearing a mask when air pollution is severe; engaging in regular aerobic exercise to improve lung capacity; maintaining good indoor ventilation; and consuming adequate antioxidants (such as vitamin C and vitamin E) through a balanced diet, as these substances help protect lung tissue from oxidative damage.

Summary | 总结

呼吸作用是生命最基本的生化过程之一，它使生物体能够将食物中的化学能转化为可直接利用的 ATP。人类的呼吸系统 – 从鼻腔到肺泡 – 经过精妙的演化，能够高效地进行气体交换，通过扩散作用将氧气输送到血液中，同时将代谢废物二氧化碳排出体外。有氧呼吸是最高效的能量获取方式，而无氧呼吸则是在氧气不足时的应急备用方案，但会产生乳酸作为副产品。植物同样进行呼吸作用，只不过它们在白天还同时进行光合作用，使气体交换的净效应变得更加复杂。运动时呼吸速率和深度的增加是身体满足能量需求升高的正常生理反应，而保护好呼吸系统免受烟雾、污染物和病原体的侵害，则是维持长期健康的关键。

Respiration is one of the most fundamental biochemical processes of life, enabling organisms to convert the chemical energy in food into directly usable ATP. The human respiratory system – from the nasal cavity to the alveoli – has evolved with remarkable precision to carry out gas exchange efficiently, delivering oxygen into the bloodstream by diffusion while removing the metabolic waste product carbon dioxide. Aerobic respiration is the most efficient way to obtain energy, while anaerobic respiration serves as an emergency backup when oxygen is insufficient, albeit producing lactic acid as a by-product. Plants also carry out respiration, but during the daytime they simultaneously perform photosynthesis, making the net effect on gas exchange more complex. The increase in breathing rate and depth during exercise is a normal physiological response to meet the elevated energy demand, and protecting the respiratory system from smoke, pollutants, and pathogens is key to maintaining long-term health.

---

更多咨询请联系16621398022（同微信）