Summary Grade 9: NS: Revision

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