跟读练习: Asthma - 通过视频学习英语口语
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Asthma is a chronic respiratory condition characterized by recurrent episodes of airway inflammation and obstruction, known as asthma attacks, which result in breathing difficulties,
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such as dry cough, wheezing, and shortness of breath.
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When you take a breath, the air travels through your nose or mouth down the trachea.
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From here, it moves into the primary bronchi, which branch into smaller secondary bronchi, then tertiary bronchi, and finally into the bronchioles.
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Bronchioles lead directly to tiny alveoli, where the gas exchange occurs.
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Now the airway walls contain smooth muscle cells and elastic tissue
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that help them open and return to their shape as we breathe.
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The lining of the airways includes epithelial cells with tiny brush-like projections called cilia and goblet cells that produce sticky mucus.
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The mucus traps dust and other unwanted particles, while the cilia move together in coordinated waves, pushing the mucus and trapped particles toward the throat.
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This system, known as the mucociliary escalator, allows us to either swallow or cough out foreign particles.
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And if the mucus traps a pathogen, immune cells in our airways step in to eliminate the threat.
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Now asthma develops when the immune system in the airways becomes hypersensitive and overreacts to triggers that should be harmless.
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Based on the underlying cause, asthma can be classified as atopic and non-atopic asthma.
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Atopic asthma, also known as allergic asthma, is the most common type of asthma.
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It usually begins when someone breathes in allergens like pollen or dust mites.
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Instead of ignoring these harmless substances, the immune system identifies them as threats.
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As a result, antigen-presenting cells in the respiratory mucosa capture the allergen through a process called phagocytosis and break it down.
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Next, they present some of its fragments, known as antigens, on their surface.
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It's their way of signaling to the immune system, we have an intruder!
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these antigens, they alert Th2 cells to release pro-inflammatory cytokines called interleukins, which signal other immune cells to jump into action.
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Interleukin-5 activates eosinophils to join the response, while interleukins-4 and 13 stimulate B cells to differentiate into plasma cells.
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Next, these plasma cells begin producing allergen-specific IgE antibodies, which latch onto mast cells.
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This process is known as sensitization, and initially it does not cause any symptoms.
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Instead, it prepares mast cells for future encounters.
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So when the body meets the same allergen again, the allergen cross-links the IgE on the surface of mast cells,
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triggering the release of histamine and other inflammatory mediators, such as leukotrienes and prostaglandins.
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This IgE-mediated immune response is known as type 1 hypersensitivity.
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The activation of mast cells and eosinophils occurs minutes after exposure to a specific allergen
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and represents the beginning of the early phase of atopic asthma.
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First, inflammatory mediators cause smooth muscle cells to contract, causing bronchospasm and narrowing of the airways.
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Second, the surrounding small blood vessels dilate and become leaky, causing local edema and further narrowing the airways.
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Third, the inflammatory response stimulates goblet cells to increase the production of thick mucus that can plug the already narrowed airways.
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Then, hours after the exposure, the late phase of atopic asthma sets in.
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During this phase, epithelial cells release chemokines to recruit more immune cells to the site.
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These include more Th2 cells and eosinophils, as well as neutrophils, basophils, lymphocytes, and monocytes.
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Meanwhile, eosinophils release substances that also damage the epithelium.
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This late phase can last for hours after the exposure, keeping the walls of airways swollen long after the initial trigger is gone.
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Now let's switch our focus to non-atopic or non-allergic asthma, which is typically associated with respiratory infections and exposure to air pollutants.
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When a pathogen, like a virus, reaches the airways, it activates the immune system, causing local inflammation.
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As the immune system fights the pathogen, it also damages the surrounding epithelial lining and the vagus nerve endings beneath it.
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This damage makes the nerve endings overly sensitive to irritants that would not typically cause a reaction.
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So besides viruses and pollutants, things like cold air, cigarette smoke, or physical activity can trigger these hypersensitive nerves and cause bronchospasm.
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And since non-atopic asthma does not involve IgE antibodies, it does not represent type 1 hypersensitivity.
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Regardless of the type, repeated inflammation causes permanent structural changes in airways called airway remodeling.
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The smooth muscle cells around the airways grow thicker and which is known as hypertrophy and hyperplasia of smooth muscle cells.
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Meanwhile, repeated inflammation and tissue damage activate fibroblasts, which deposit collagen, causing fibrosis of the airway walls.
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Goblet cells also grow in size, ramping up mucus production.
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The excess mucus and sloughed mucosal epithelial cells can form thick plugs known as Kirschman spirals.
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Next, as eosinophils break down, they release a protein called galactin-10, which forms needle-like crystals in the mucus called charcolidin crystals.
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In severe cases, thick mucus can completely block airflow, trapping air inside the alveoli and causing them to over-inflate like tiny balloons.
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Finally, immune cells release substances that promote blood vessel growth in the submucosa.
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Now, because the inflammation in the airways comes in waves, symptoms tend to show up in episodes or what we call asthma attacks.
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During an attack, often the first sign is a dry cough.
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On top of that, as a person tries to breathe out, the air is forced through narrow airways, creating the classic high-pitched whistling sound called wheezing.
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Usually this is heard most clearly during expiration.
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Also, you might notice prolonged expiration because a person takes longer to blow the air out.
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And because the airways are tight, fresh air can't reach the alveoli, which reduces oxygen delivery to the lungs, causing shortness of breath.
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To compensate for this lack of air, a person will usually breathe much faster and use accessory muscles to help with breathing.
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Many individuals also describe the feeling of chest tightness, like a heavy band squeezing around their chest.
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And because of these breathing difficulties, a person often has a hard time speaking in full sentences.
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Finally, in severe cases, oxygen levels in the blood can drop, causing a bluish discoloration around the lips called cyanosis.
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Once an asthma attack settles down, most people feel fine.
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But for some, subtle symptoms persist.
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These often follow a diurnal pattern, appearing early in the morning or late at night.
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A common symptom is a dry cough, which may occur late at night and disturb sleep.
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Others might experience mild shortness of breath along with coughing during physical activity.
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All these features are suggestive of asthma, but you need to determine the type and confirm the diagnosis.
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Atopic asthma often appears alongside other allergic conditions.
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Many individuals early in life first experience atopic dermatitis, followed by allergic rhinitis, and eventually develop breathing difficulties suggestive of atopic asthma.
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This pattern of progression is known as the atopic merch.
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Next, allergen testing, such as a skin prick test, often shows a person is overreacting to everyday allergens.
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And if you check IgE levels, they are typically high because B-cells are pumping these antibodies to gear up the immune system for future exposures.
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Finally, be sure to check how well the lungs are working using spirometry.
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This test will reveal that a person can't blow out as much air in one second as they should.
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However, the key clue is that after they use a bronchodilator, which helps relax the airways, they can suddenly breathe out a lot more air.
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This reversibility points to asthma.
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On the other hand, in non-atopic asthma, there's no history of allergies, and allergy testing is typically negative.
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Instead, these individuals report that their symptoms show up during respiratory infections, physical activity, times of stress,
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or even when breathing cold air.
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And just like with atopic asthma, spirometry shows the same breathing pattern, meaning a person has trouble blowing out air, which improves after using a bronchodilator.
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In both types, the management of asthma attacks involves inhalation of short-acting beta-agonists like albuterol.
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These medications relax smooth muscle cells in the airways, causing bronchodilation and making breathing much easier.
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Additionally, systemic corticosteroids can help reduce airway inflammation.
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On the other hand, long-term management aims to keep the inflammation in check and prevent future asthma attacks.
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That's where low doses of inhaled corticosteroids and long-acting beta-agonists come in.
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Alright, as a quick recap, asthma is a chronic respiratory condition characterized by recurrent episodes of airway inflammation and obstruction,
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known as asthma attacks, which result in breathing difficulties such as dry cough, wheezing, and shortness of breath.
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Atopic asthma is triggered by allergens and involves an IgE-mediated type 1 hypersensitivity response.
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In contrast, non-atopic asthma is associated with respiratory infections and air pollutants, and it's triggered by things like cold air, stress, or physical activity.
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Thank you.
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本课的词汇与口语要点
视频中反复出现的词有：asthma, cells, airway, atopic, immune。 这段视频共有 93 个句子、1497 个单词可供跟读。 讲话部分时长为 10:17。 说话人语速平稳，每分钟约 145 个词，很适合跟读。 只有 66% 的单词属于英语最常用的 3,000 词，词汇难度较高。
视频中的重点词汇
视频中最难的 15 个单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| asthma 名词 | /ˈæzmə/ | 哮喘, 氣喘 /气喘 |
| airway 名词 | /ˈɛɚ.weɪ/ | 空中航線 /空中航线 |
| allergen 名词 | /ˈælə(ɹ)ˌd͡ʒɛn/ | 變應原 /变应原, 過敏原 /过敏原 |
| mucus 名词 | /ˈmjuːkəs/ | 黏液 |
| inflammation 名词 | /ɪnfləˈmeɪ̯ʃən/ | 炎症, 發炎 /发炎 |
| respiratory 形容词 | /ɹɪˈspɪ.ɹət.ə.ɹi/ | 呼吸的 |
| symptom 名词 | /ˈsɪm(p)təm/ | 症狀 /症状, 病徵 /病征 |
| mast 名词 | /mɑːst/ | 桅, 桅杆 |
| inflammatory 形容词 | /ɪnˈflæmət(ə)ɹi/ | 激發性 /激发性 |
| allergic 形容词 | /əˈlɝ.d͡ʒɪk/ | 過敏的 /过敏的, 過敏性的 /过敏性的 |
| alveolus 名词 | /ælˈvi.əl.əs/ | 肺泡 |
| antibody 名词 | /ˈæn.tɪˌbɑ.di/ | 抗體 /抗体 |
| antigen 名词 | 抗原 | |
| bronchus 名词 | /ˈbɹɑŋkəs/ | 支氣管 /支气管 |
| goblet 名词 | /ˈɡɒblət/ | 高脚杯 |
视频中出现的短语动词
| 单词 | 释义 |
|---|---|
| break down 动词 | 壞了 /坏了, 出故障 |
| settle down 动词 | 冷靜下來 /冷静下来 |
| show up 动词 | 露面 |
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | can be classified · is known · is forced |
| 定语从句 who / which + 从句 — 补充说明人或事物 | asthma, which is · and which is |
需要注意的发音
- “th” 音: pathogen /ˈpæθəd͡ʒn̩/, epithelium /ˌɛpɪˈθiːlɪəm/
- “sh” 和 “zh” 音: inflammation /ɪnfləˈmeɪ̯ʃən/, expiration /ˌɛk.spɚˈeɪ̯.ʃən/, obstruction /əbˈstɹʌk.ʃən/, bluish /ˈbluːɪʃ/, tertiary /ˈtɜː.ʃi.ə.ɹiː/
- 长单词——注意重音位置: inflammation /ɪnfləˈmeɪ̯ʃən/, respiratory /ɹɪˈspɪ.ɹət.ə.ɹi/, eosinophil /i.əˈsɪnəˌfɪl/, inflammatory /ɪnˈflæmət(ə)ɹi/, alveolus /ælˈvi.əl.əs/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 用正常速度逐句跟读，每句重复到你的节奏与说话人一致为止。
- 录下自己的声音并与原声对比，特别注意 asthma, airway, allergen 这类单词。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。