Ventilation

Ventilation

Getting air in and out of the lungs

Muscles involved in ventilation

• The diaphragm

• The intercostal muscle (internal & external : antagonistic), found between and attached to the ribs

• Abdominal muscles

When we inhale

The volume of our thoracic cavity increases. Pressure inside the lungs decreases.

When we exhale

The volume of our thoracic cavity decreases. Pressure inside the lungs increases.

During inspiration

1. The diaphragm contracts & moves downward

2. The external intercostal muscles contract causing the ribcage to move up and out

3. Volume of the thoracic cavity increases, pressure in lungs decreases

4. As a result, air moves down its pressure gradient into the lungs

During quiet breathing expiration

1. The diaphragm relaxes, moving upwards and inwards

2. The external & internal intercostal muscles relax, causing the ribcage to move down and in

3. Causes decreased volume of thoracic cavity so pressure increases

4. Air moves down its pressure gradient out of the lungs

During forced breathing expiration

1. The diaphragm relaxes, moving upwards and inwards

2. The external intercostal muscle relax and the internal intercoastal muscles contract, causing the ribcage to move down and in forcefully

3. Causes decreased volume of thoracic cavity so pressure increases

4. Air moves down its pressure gradient out of the lungs forcefully

Forced vital capacity

The volume of air that you can forcefully exhale

Residual volume

The volume of air remaining in the lungs that cannot be exhaled as our lungs would collapse without it

Tidal volume

The volume of air that move in and out of the lungs with each normal breath

Inspiratory reserve

The additional volume of air you can inhale after a normal breath

Expiratory reserve

The additional volume of air you can exhale after a normal breath

Factors that affect human lung capacity

• Age, decreases after 25

• Body composition, larger people have larger lungs

• Biological sex

• Respiratory disease

• Levels of physical activity

Spirometery

A pulmonary function test that measures the volume and speed of air that a person can exhale