Respiratory System
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Respiratory System Overview

The Respiratory System is everything we use to breathe and supply our bodies with oxygen.

  • We breath air into our lungs.
  • Oxygen is then transported around our body by our blood.
  • Air passes through the nose or mouth into the trachea
  • The trachea splits into 2 tubes called the bronchi, one going to each lung
  • The bronchi split into smaller tubes, called the bronchioles
  • The bronchioles end up at small bags called the alveoli, where gaseous exchange takes place.



Breathing in (inspiration)

  • The intercostal muscles and diaphragm contract to widen the chest cavity
  • Air is pushed into the lungs by the air pressure outside

Breathing out (expiration)

  • The intercostal muscles and diaphragm relax to make the chest cavity smaller
  • The lungs are squeezed and air is forced out

When you exercise, your body needs more oxygen to make the muscles work. Therefore, you breath more quickly and your heart pumps faster, so the red blood cells can travel faster to deliver more oxygen. This increases your O2 uptake.



There are millions of alveoli in our lungs, where gaseous exchange takes place.

When we breath, Carbon dioxide (CO2) moves from the blood into the alveoli. Oxygen (O2)moves to the red blood cells, which contain haemoglobin. This combines with the O2 to make oxyhaemoglobin. The red blood cells carry O2 around the body, taking it to where its needed. Whilst this is taking place, the blood collects the CO2 to take it back to the lungs.

The air we breath out has less O2, because the body has used some of it up through the respiration process.


Gaseous exchange in the lungs

The composition of inhaled and exhaled air are compared and the anatomy of the respiratory surface is described. Using an animation, the presenters describe how gaseous exchange takes place. The adaptations of the alveoli are explained: large surface area, moist, thin walls, good blood supply.

Aerobic Training

Aerobic training can help in the following ways:

  • The diaphragm and intercostal muscles get stronger, making the chest cavity large
  • Therefore, more air can be breathed in, so your vital capacity increases
  • More capillaries grow around the alveoli, so more CO2 and O2 can be swapped at any time
  • Gas exchange is quicker, so vigorous exercise can be kept up

Here is a video explaining how the Circulatory and Respiratory Systems work


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