8Cb Gas exchange system
LO: Describe the structure and function of the human gas exchange system.
Model Answers
The human respiratory system contains the organs that allow us
to get the oxygen we need and to remove the waste carbon
dioxide we do not need. It contains these parts:

two lungs

tubes leading from the mouth and nose to the lungs

diaphragm - a large sheet of muscle that separates the
lungs from the abdominal cavity.

Intercostal muscles - sets of muscles between the ribs
which raise and lower the rib cage.
Connecting the outside to the inside
Air passes from the mouth into the trachea, often called the windpipe. The trachea divides into two bronchi,
with one bronchus for each lung.
Each bronchus divides further in the lungs into smaller tubes called bronchioles. At the end of each bronchiole,
there is a group of tiny air sacs. These air sacs have bulges called alveoli to increase their surface area.
Ventilation
Ventilation or breathing involves movements of the ribs, intercostal muscles and diaphragm to move air into and
out of the lungs:

when we breathe in, we inhale

when we breathe out, we exhale
The table describes the changes
involved:
Independent Practice
1. What gas do we need, and which is waste?
2. What organs are involved in the respiratory system?
3. Describe the passage of air around the respiratory system entering
the mouth.
4. What is it called when we breathe in?
5. What is it called when we breathe out?
6. What is the diaphragm?
7. Explain how the diagram moves when we inhale and exhale.
8. What are the intercostal muscles?
9. Explain how the intercostal muscles move when we inhale and
exhale.
10. How is the pressure inside the chest different when we inhale
compared to when we exhale?
Challenge
Conditions such as asthma
narrow the airways that carry air
into the lungs.
Explain how this would make
breathing difficult.
Use the correct terms for each
structure.
Assessment:
Independent Practice
1)
2)
3)
4)
5)
6)
7)
8)
9)
We need oxygen and carbon dioxide is the waste gas.
Lungs
Mouth – trachea – bronchi – bronchioles – alveoli.
Inhale
Exhale
A large sheet of muscle that separates the lungs from the abdominal cavity.
When we inhale the diaphragm moves downwards, when we exhale it moves upwards.
A set of muscles between the ribs which raise and lower the rib cage.
When we inhale the ribs contract and raise the ribs, when we exhale they relax letting the ribcage move
down.
10) When in inhale the pressure is decreased below atmospheric pressure, when we exhale the pressure is
above atmospheric pressure.
Challenge Task
Swelling of the bronchi and bronchioles will reduce the airflow that can pass through them meaning less
air can get to the alveoli for gas exchange.