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Structure & Function of the Gas Exchange System

Science: KS3, topic 1.6.15

Structure and Function of the Gas Exchange System

The gas exchange system in humans is about the inhaling of oxygen and the exhaling of carbon dioxide.

Respiration

Respiration

  • Aerobic respiration is a chemical reaction.
  • Respiration converts glucose and oxygen into carbon dioxide and water.
  • Respiration is different from breathing.
  • Breathing is the inhaling of oxygen and the exhaling of carbon dioxide.
  • Respiration occurs in organelles called mitochondria.
The gas exchange system

The gas exchange system

  • Air is inhaled through the mouth.
  • Air enters the trachea.
  • The trachea is also called the windpipe.
  • The trachea splits into two bronchi.
  • The left bronchus goes into the left lung.
  • The right bronchus goes into the right lung.
  • In each lung, the bronchus splits into over 30000 bronchioles.
  • Alveoli are at the tips of the bronchioles.
Alveoli

Alveoli

  • Alveoli are air sacs in the lungs
  • Alveoli are where the gas exchange takes place.
  • Oxygen enters the blood at the alveoli.
  • Oxygen flows from the alveoli to the heart.
  • The heart pumps blood with oxygen in it around the body.
  • Carbon dioxide leaves the blood through the alveoli.
Alveoli walls

Alveoli walls

  • To maximise the gas exchange, alveoli have very thin walls.
  • Alveoli walls are only one cell thick.
  • The thin alveoli walls allow more efficient diffusion of oxygen and carbon dioxide.
  • Alveoli walls are moist and permeable
  • Gases can dissolve and pass through the Alveoli.
The diaphragm

The diaphragm

  • The diaphragm is an important muscle for breathing.
  • When you inhale, the diaphragm contracts.
  • The contracted diaphragm creates more volume within the ribcage.
  • The increased volume allows more air into the lungs.
  • When you exhale, the diaphragm relaxes.
  • The relaxed diaphragm reduces the volume within the ribcage.
  • As the ribcage volume decreases, air is pushed out of the lungs.

Test yourself on Structure & Function of the Gas Exchange System

  • What happens when you inhale?

  • What would happen if the diaphragm did not contract during inhaling?

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