Summary
Summary Grade 9: NS: Revision
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- Natural Sciences
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- 9
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Respiratory system: Responsible for supplying oxygen to the body and removing carbon dioxide.
Respiration takes place in the living cells and requires oxygen to take place, and
for carbon dioxide to be given off. The trachea is the tube which air travels
through into the lungs. It splits into the left and right bronchi, which further
branch into smaller tubes. These all end up in the hollow cavities called alveoli.
Components:
Nose
Mouth
Trachea
Bronchi
Bronchiole
Lungs
Main processes:
Breathing
Air contains a mixture of gases
Breathing is a process during which oxygen is inhaled and carbon dioxide is
exhaled
It is an active process – air flows in and out of the lungs as a result of
differences in air pressure between the lungs and air outside the body
Inhalation and Exhalation
During inhalation the following takes place: The rib cage moves upwards
and outwards. The diaphragm contracts and flattens causing it to move
downwards
This causes the chest volume to increase and the pressure decreases
As a result the lungs are also pulled to become bigger
This allows the air to be pulled into the extra space inside the lungs
During exhalation the following takes place: The rib cage moves
downwards and inwards
The diaphragm also relaxes, causing it to become more dome-shaped
This causes the chest volume to decrease and the pressure increases
As a result the lungs are squeezed smaller
This forces the air out of the lungs
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