Breathing
Overzicht
You have taken roughly twenty thousand breaths since this time yesterday and noticed almost none of them. Every one of them ran the same errand: bringing fresh air close enough to your blood for oxygen to cross into it, and carrying away the carbon dioxide your cells have finished with. Nothing pumps those gases across. They move by diffusion, which is slow and works only over very short distances, so the body has to build a surface that makes it fast.
This lesson takes that surface apart. You will name the eight structures the specification asks you to recognise on a diagram of the respiratory system, follow air down the branching tubes from the trachea to the alveoli, and work out why a gas exchange surface the size of a badminton court is folded up inside your ribcage. Along the way you will see why an organism the size of you cannot do what a single cell does and simply swap gases across its own outer surface.
Doelstellingen
- The respiratory (breathing) system takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air. The lungs are in the upper part of the body (thorax), protected by the ribcage and separated from the lower part of the body (abdomen) by the diaphragm. Students should be able to recognise the following on a diagram of the respiratory system: ribs, intercostal muscles, diaphragm, lungs, trachea, bronchi, bronchioles, alveoli.
- The alveoli provide a very large surface area, richly supplied with blood capillaries, so that gases can readily diffuse into and out of the blood.
Mindmap
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Lesevaluatie
Gefeliciteerd met het voltooien van de les op Breathing. Nu je de sleutelconcepten en ideeën, het is tijd om uw kennis op de proef te stellen. Deze sectie biedt een verscheidenheid aan oefeningen vragen die bedoeld zijn om uw begrip te vergroten en u te helpen uw begrip van de stof te peilen.
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- Which structure separates the thorax from the abdomen? A. The ribcage B. The diaphragm C. The trachea D. The bronchioles Answer: B
- In which order does air pass through these structures on its way into the lungs? A. Trachea, bronchiole, bronchus, alveolus B. Trachea, bronchus, bronchiole, alveolus C. Bronchus, trachea, alveolus, bronchiole D. Bronchiole, bronchus, trachea, alveolus Answer: B
- Approximately what percentage of exhaled air is carbon dioxide? A. 0.04% B. 4% C. 16% D. 21% Answer: B
- Which feature of the alveoli most increases the rate at which oxygen diffuses into the blood? A. Rings of cartilage that hold them open B. A large surface area with walls one cell thick and many capillaries C. A thick layer of muscle in their walls D. Cilia that sweep mucus away from them Answer: B
- A single-celled organism needs no gas exchange system. Why? A. It does not respire B. It has a relatively large surface area compared with its volume C. It makes its own oxygen D. Its surface membrane is thicker than an alveolus wall Answer: B
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