AS AQA Unit 1 Biology - Lungs


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Alveoli- Contain collagen, elastic fibres and lined with epithelium. Elastic fibres allow them to stretch and fill with air and spring back to expel CO2.

Bronchi- Cartalidge gets reduced as it gets smaller. Produce musus and have cilia.

Trachea-  Supported by rings of cartalidge.

Rib Cage- Supports and protects the lungs.

Bronchioles- Branching sub-divisions of bronchi. Muscle controls the amount of air which goes into the alveoli.

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Macrophages- Found in the alveoli and defend body by bacteria.

Blood Vessels- Warm incoming air.

Surfactant Cells- Cells of the alveoli that produce a phospholipid, release a rich secretion on the surface of the alveoli, minimizes friction.

Hairs- Trap and filter dust particles.

Ciliated Epithelial Cells- Have goblet cells which produce mucus to trap dust particles.

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  • Intercostal muscles relax.
  • Ribs and Sternum move down and in.
  • Diaphragm muscles relax.
  • Diaphragm more up (domed shape).
  • Thorax volume decreases.
  • Gas pressure in the thorax increases.
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  • Intercostal muscles contract.
  • Ribs and sturnum move up and out.
  • Diaphragm muscles contract.
  • Diaphragm move down (flattens)
  • Thorax volume increases
  • Gas pressure in the thorax decreases.
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Lung Diseases- Asthma

  • Triggered by dust, smoke, pollution and cold air.
  • Symptoms:- coughing, wheezing, shortness of breath.
  • Smooth muscle contracts (spasms) which produces more mucus than normal, so airways become narrow, which in turn reduces ventilation and airflow is less efficient.
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Lung Diseases- Emphysema

  • Alveoli walls are damaged and replaced by connective tissue.
  • Permanently stretches the elastin- does not force the air out of the alveoli. 
  • Surface area of alveoli is reduced.
  • Symptoms:- chronic cough, shortness of breath, blue colouration to skin due to lack of oxygen.
  • Caused by smoking and pollution.
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