4. Breathing

Success Criteria

Your learning has been successful if you can do the following:

I can define ‘breathing’.
I can explain how ‘breathing in’ happens.
I can explain how ‘breathing out’ happens.

Vocabulary

Learn these so you can communicate this concept well.

Inhalation: What happens as a result of increased volume and decreased pressure inside the chest.
Exhalation: What happens as a result of decreased volume and increased pressure inside the chest.
Intercostal muscles: Raises and lowers the ribs to help with breathing.
Diaphragm: Contracts and relaxes to increase and decrease the chest volume.
Ribs: Bones that protect the lungs.
Breathing: Movement of air into and out of the lungs.

Hei Mahi (Do Now)

Do Now in your Learning Journal:

Think back to the previous lesson. Arrange these parts in the order that air travels through when breathing in:

bronchioles, nose, alveoli, traceha, bronchi

Exit Task

In your Learning Journal:

Re-write this interpreting question so it is asking about Breathing:

What is the cause?

Then, write an answer for it.

What is breathing?

BREATHING is the contracting and relaxing of the intercostal muscles and the diaphragm muscle to physically move air into and out of the lungs.

Breathing in (Inhalation)

To get air to flow into the lungs the area inside the chest cavity needs to be increased. This happens when:

The INTERCOSTAL MUSCLES are the muscles between the ribs. When the muscles contract the rib bones are moved up and outwards – increasing the area inside the chest.
The DIAPHRAGM is a sheet of muscle across the base of the lungs. When the diaphragm contracts the diaphragm moves down – creating more area inside the chest.

As a result, the volume of the chest cavity increases and forces air to move air into the lung to equalise the air pressure inside and outside the lungs.

Breathing out (Exhalation)

Breathing out happens when all of the muscles relax and the volume of the chest cavity decreases. Air rushes out as there is less space in the lungs for the air that is in there.

The intercostal muscles relax and the ribs move in and downwards – decreasing the area of the chest.
The diaphragm relaxes and moves up – decreasing the area inside of the chest.

The volume of the chest cavity has decreased and air is pushed out of the lungs to equalise the air pressure.

A bell jar can be used to model breathing, where the bell jar represents the chest cavity, the glass Y tube represents the airways, the balloons represent the lungs, and the rubber sheath represents the diaphragm.