Flashcards · 9700 · AS Topic 9

Gas exchange (AS Level) flashcards

6 cards on AS Topic 9. Pick a subtopic or study them all.

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How does cartilage differ in the trachea, bronchi and bronchioles?: Trachea: C-shaped rings. Bronchi: irregular plates. Bronchioles: none. Cartilage keeps the airways open so they do not collapse.
Role of goblet cells and cilia: Goblet cells (and mucous glands) secrete mucus, which traps dust, pollen and pathogens. Cilia beat to move the mucus up to the throat, where it is swallowed. Cilia do not trap anything.
Smooth muscle vs elastic fibres in the gas exchange system: Smooth muscle contracts to narrow and relaxes to widen bronchi and bronchioles, controlling airflow. Elastic fibres stretch as alveoli fill and recoil to help expel air; they are not muscle.
How do you identify a bronchiole in a micrograph?: No cartilage visible, a ring of smooth muscle and a folded lining of ciliated epithelium.
Why is gas exchange in the alveoli efficient?: Large surface area; short diffusion distance (squamous epithelium + capillary endothelium); narrow capillaries; steep gradients kept by blood flow and breathing; moist surface.
Path of oxygen from alveolus to blood: Alveolar air → alveolar wall (squamous epithelium) → capillary wall → plasma → red blood cell, where it binds haemoglobin. By diffusion down a partial pressure gradient.