Exam 4 (#23) - External Respiration

What makes up the cells of alveoli?

• Type 1 cells

• Type 2 cells

• Alveolar macrophages

Explain type 1 vs type 2 cells of alveoli:

Type 1 cells:

• Most abundant cells

• Endothelium

Type 2 cells:

• Produce surfactant

• Divide to produce type 1

Explain alveolar macrophages in the alveoli:

Alveolar macrophages:

• Phagocytes

• Resident cells

Explain surface tension in alveoli:

Lungs use surfactant

• Reduces surface tension

= weakens bonds between water molecules

What does the surfactant do? (in relation to alveoli)

It blocks surface tension & keeps alveoli from collapsing

What does water “like” to interact with?

Other water molecules

What happens in the alveolis?

Water accumulates (humidified air)

What is the respiratory membrane?

The interface between air and blood

• The closest air and blood can ever be touching

• Essential for has diffusion (CO2 & O2)

What are the layers of the respiratory membrane?

A = lumen of alveolar sac

E - endothelium (alveolus)

BL = connective tissue

EC = endothelium (capillary)

Why do the gasses move across the respiratory membrane?

Because of the differences in partial pressure

What is the percent of each gas in the air we breath?

N2 = ~78%

O2 = ~21%

CO2 = ~0.035%

What is Dalton’s law of partial pressure?

The partial pressure of a gas is proportional to the percentage of that gas in the mixture

What is made when partial pressures of gases are added up?

They add up to make the total atmospheric pressure

A planet’s air has:

(P)CO2: 60 mmHg

(P)O2: 35 mmHg

(P)N2: 5 mmHg

What is the atmospheric pressure?

P atm = 100 mmHg

What is Henry’s law?

Gas will dissolve into a liquid in proportion to its partial pressure

(explains how gas moves across the membrane)

What does a higher pressure difference mean?

Movement into solution = more and faster

Where does external respiration occur at?

The interface of gas (air) and liquid (blood)

• Specifically alveolar

Does blood oxygenate quickly or slowly? How long does it take?

Blood oxygenates quickly - it takes about 0.25 seconds

How long does it take for a red blood cell to pass through a capillary

It takes about 0.75 seconds

How does altitude directly affect respiration?

It affects:

• gas partial pressures

• oxygen loading

Explain pneumonia:

H2O buildup

• Increased respiratory membrane thickness

Explain emphysema:

Less surface area in alveolus