How and why Gas Exchange happens:

Location: The alveoli

Method: Diffusion

KEY WORDS:

• Partial pressure: In a mixture of gases such as air or blood, each gas accounts for a portion of the total pressure the mixture produces. The amount of pressure each gas contributes is the partial pressure.

EXAMPLE Partial Pressures:

Partia

l Pre

ssure

s:

How does this happen?

• Oxygen that you breathe in from the atmosphere when it reaches your alveoli has a partial pressure of PO2= 104mm Hg.

• The partial pressure of Oxygen in your bloodstream from this point is only 40mm Hg.

Diffusion of Gases:

FIRST- why is the blood stream partial pressure of oxygen so low?

SECOND- where will the oxygen want to

diffuse to? Think about what we know about diffusion already.

1. When blood reaches the alveolus / lungs the blood is oxygen poor- it has depleted its oxygen source to the rest of the body and needs to “pick up more”.

2. The oxygen will diffuse from an area of high concentration to low or from the alveoli into the blood stream. Which will now make it oxygen rich and travel to other tissues and cells.

• Explain than what is going on with the Carbon dioxide?

• Why is carbon dioxide higher in the blood capillaries?

• With the help of diffusion where does the Carbon dioxide go?

• Label the following diagram:

How does pressure or altitude affect breathing? WHY?

• Why do my ears pop? If you've ever been to the top of a tall mountain, you may have noticed that your ears pop and you need to breathe more often than when you're at sea level. As the number of molecules of air around you decreases, the air pressure decreases. This causes your ears to pop in order to balance the pressure between the outside and inside of your ear. Since you are breathing fewer molecules of oxygen, you need to breathe faster to bring the few molecules there are into your lungs to make up for the deficit.

LUNG CAPACITIES

KEY TERMS: • Respiratory cycleRespiratory cycle: One inspiration plus one

expiriation. (Breathe in- breathe out)

• Resting Tidal volume- Resting Tidal volume- the normal amount of air that enters the lungs and leaves the lungs during a respiratory cycle.

• The average is about 500 milliliters of air per breath in and the same amount out.

• During Tidal volume you do not use the total amount of space in your lungs! They only use about 75-80%

KEY TERMS:

• Inspiratory Reserve VolumeInspiratory Reserve Volume: When you take a deep breath in to hold more air than a usual breath. “Forced inhalation”.

• Expiratory Reserve VolumeExpiratory Reserve Volume: Forced expiration. Expelling air beyond the tidal volume. Even after the most forceful exhale however you still have air left in your lungs.

• This left over air is called the Residual VolumeResidual Volume.

KEY TERMS:

• Vital Capacity: Vital Capacity: Combing the tidal volume with both the inspiratory reserve volume and the expiratory reserve volume.

• Total Lung CapacityTotal Lung Capacity: The vital capacity plus the residual volume. All the possible air that can come into or out of the lungs, including the air that never leaves the lungs.

Fill in the following table with the appropriate terms: