The Breathing System

L/O ;- To be able to label the human breathing system

‘When it is cold your blood vessels shrink away from your fingers and toes so that they can keep the heart and vital organs

warm’

Use this sentence to explain why people get frostbite (think level 6)

Gaseous Exchange The lungs are not empty bags, the are full with little air sacs called alveoli. This is where the oxygen diffuses into the blood and the carbon dioxide diffuses out

To improve the gaseous exchange the alveoli have;-

• A large surface area • A moist surface • A large network of capillaries

The gases move by diffusion - net movement from a [high] to [low]

• Oxygen diffuses from air in alveoli into blood• Carbon dioxide diffuses from blood into air in alveoli• Some water vapour is also lost from the surface of the

alveoli

Complete the worksheet and stick in

Capillaries surround the air sacsGas exchange occurs in the lungsPlasma carries CO2 within the blood

O2

CO2

Cilia• There are also specialised cells in the lining of the breathing

tubes which produce a sticky mucus to trap dirt and microbes• Specialised cells called cilia help to move this mucus out of

the lungs• Smoking can damage these delicate cells (hot smoke and tar)

and they are less effective• This is why smokers cough a lot, trying to move this mucus

Cilia

Summary• The breathing system allows for gas exchange - it needs to

be as efficient as possible (alveoli have thin walls and very large surface areas - area the same as a tennis court)!

Summary• Oxygen is transferred into the blood, and carbon dioxide

out of it via diffusion (net movement from high concentration to low concentration)