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1. Importance of Breathing
│ ➔ Supplies O₂, removes CO₂.
│ ➔ Humans rely on active breathing (not diffusion).
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2. Structure of the Respiratory System
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├─ Nasal Passages: Filter, warm, moisten air.
├─ Trachea: C-shaped cartilage, cilia, mucus.
├─ Larynx: Voice production.
├─ Bronchi/Bronchioles: Branch into lungs.
└─ Alveoli: Gas exchange site (large surface area + capillaries).
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3. Breathing Mechanism
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├─ Inhalation
│ ├─ Diaphragm contracts (flattens).
│ ├─ Ribs rise (external intercostals contract).
│ └─ Thoracic volume ↑ → air enters.
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└─ Exhalation
├─ Diaphragm relaxes (domes up).
├─ Ribs drop (gravity/internal intercostals).
└─ Thoracic volume ↓ → air exits.
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4. Gas Exchange in Alveoli
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├─ Requirements: Moist surfaces, short diffusion distance, rich blood supply.
├─ Process:
│ ├─ O₂ diffuses into blood.
│ └─ CO₂ diffuses out of blood.
└─ Air Composition:
├─ Inhaled: 21% O₂, 0.04% CO₂.
└─ Exhaled: 16% O₂, 4% CO₂.
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5. Factors Affecting Breathing Rate
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├─ Exercise → ↑ O₂ demand.
├─ Anxiety → "Fight or flight" response.
├─ Drugs: Stimulants ↑ rate; depressants ↓ rate.
├─ Altitude → Low O₂ → ↑ breathing.
├─ Weight → Restricted diaphragm movement.
└─ Smoking → Damages lungs (see below).
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6. Effects of Smoking
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├─ Chemicals:
│ ├─ Nicotine (addictive).
│ ├─ CO (reduces O₂ transport).
│ └─ Tar (carcinogen; paralyzes cilia).
├─ Diseases:
│ ├─ Bronchitis, COPD, lung cancer (90% smoking-linked).
│ └─ Heart disease.
└─ Economic Impact: Healthcare costs, lost income.
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7. Breathing Hygiene & Artificial Respiration
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├─ Hygiene:
│ ├─ Cover mouth when coughing/sneezing.
│ ├─ Oral hygiene.
│ └─ Avoid smoking/shisha.
└─ Artificial Respiration:
├─ Clear airway.
├─ Tilt head, pinch nostrils.
└─ 12 breaths/minute.
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Key Definitions
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├─ Tidal Volume: ~500 mL at rest.
├─ Vital Capacity: Max air volume.
└─ Diaphragm: Muscle controlling breathing.
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