The Lungs

The Lungs

Key Adaptions for Gas Exchange:

• presence of surfactant

• high surface area

• diaphragm and intercostal muscles

• thin respiratory membrane

What are alveoli covered with?

A thin layer of pulmonary surfactant (a protein/lipid liquid)

What is the role of pulmonary surfactant in the alveoli?

It reduces surface tension in the alveoli, making it easier for oxygen and carbon dioxide to diffuse in and out of the lungs.

How does high surface area contribute to gas exchange?

A high surface area provided by many bronchioles and extensive capillary beds increases the efficiency of gas exchange.

What does the diaphragm and intercostal muscles control?

The movement of air expanding and contracting to create pressure gradients

How thick are the respiratory membranes lining the alveoli and capillaries?

One cell thick to enhance gas exchange

Antagonistic muscle pairs

When one muscle contracts, the other relaxes

What happens during inspiration?

The pressure in the chest is less than the atmospheric pressure, causing air to move into the lungs.

What occurs during expiration?

The pressure in the chest is greater than the atmospheric pressure, resulting in air moving out of the lungs.

Inhalation

Diaphragm

External intercostal muscles

Volume of the lungs

Pressure of the lungs

Air

Diaphragm - contracts

External intercostal muscles - contract

Volume of the lungs - increases

Pressure of the lungs - decreases

Air - enters

Exhalation

Diaphragm

External intercostal muscles

Volume of the lungs

Pressure of the lungs

Air

Diaphragm - relaxes

External intercostal muscles - relaxes

Volume of the lungs - decreases

Pressure of the lungs - increases

Air - leaves

When to the internal intercostal muscles also contract?

During long or forced exhalations

What contracts to push the diaphragm upward?

Additional abdominal muscles

Techniques for measuring ventilation rate or lung tidal volume:

• observation

• chest belt and pressure meter

• spirometer

Observation

Count the number of breaths per second

Chest belt and pressure meter

Recording the rise and fall of the chest

Spirometer

Records the volume of gas expelled per breath

Inhalation + exhalation

What is ventilation rate?

The number of breaths per minute

What allows for more continuous gas exchange?

Greater frequency of breaths

What is tidal volume?

The total volume of air that moves in or out of the lungs with each breath.

What allows more gas exchange?

Deeper breaths

What is vital capacity?

The maximum amount of air you can inhale and exhale in one breath.

Expiratory reserve

Extra air you breath in or out after normal inhalation or exhalation

Total lung capacity

The maximum volume of air your lungs can hold

Residual volume

The volume of air that remains in your lungs after exhalaing

How does exercise affect ventilation?

• Increases ventilation rate

• Increases tidal volume

• Over time enhance vital capacity and expiratory reserve.