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CP Exam 2 > Respiratory Sysytem and Gas Exchange part 2 (slides 50-) > Flashcards

Respiratory Sysytem and Gas Exchange part 2 (slides 50-) Flashcards

1
Q

So, how much gas is exchanged every minute-Translation-What is “J”?

- Under normal resting conditions:
    - ml of O2 exchanged every minute?
    - ml of CO2 exchanged every minute?
A
  • 250 ml of O2 exchanged every minute
  • 200 ml of CO2 exchanged every minute
  • They ARE NOT EQUAL!
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2
Q

First lesson about gas exchange?

A

The diffusion of each gas (O2 and CO2) is INDEPENDENT of one another

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3
Q

2 factors from alveolar gas exchange equation that depend directly on the structure of the alveolus?

A

Surface area and diffusion distance (thickness of alveolar barrier)

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4
Q

Alveolar gas exchange

-Equation and what is each variable?

A

J = ((S.A.) x D x (P1-P2))/distance
J: diffusion rate in ml/min
D:diffusion coefficient for each gas
(P1-P2): pressure gradient across alveolar membrane
S.A.:surface area available for diffusion
distance: diffusion distance (thickness of alveolar barrier)
Equation is solved for each gas individually

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5
Q

Alveoli

A
  • Thin-walled structures

- In a typical section of lung tissue, most of the tissue sample will be composed of alveoli

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6
Q

Alveoli-Separated by?

A
  • Alveoli are separated by interalveolar septa that consist of two simple squamous epithelial layers with an interstitium (non-fenestrated capillaries embedded in an elastic connective tissue) between them
  • The structure of the walls enhances diffusion and gas exchange
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7
Q

The alveolar epithelium consists of two cell types lining the surface of the capillaries (terminal branches of the pulmonary artery) and the alveolar wall

A

Type I and type II alveolar cells

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8
Q

Type I alveolar cells

A

Represent about 40% of the alveolar epithelial cell population and cover 90% of the alveolar surface

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9
Q

Type II alveolar cells

A
  • Represent about 60% of the alveolar epithelial cell population but cover only 10% of the surface
  • Preferentially located at the angles formed by adjacent alveolar septa
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10
Q

Type II alveolar cell function?

A

Produce surfactant

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11
Q

Alveolar macrophages (dust cells)

  • Part of?
  • Where are they located?
A
  • Part of the mononuclear phagocyte system
  • Found along the alveolar surface, within the interstitium
  • Often seen detached in alveolar lumen of histological sections
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12
Q 
Alveolar macrophages (dust cells)
   -Function?
A
  • Remove debris that escapes mucus and cilia in the conducting portion of the system
  • Many migrate to bronchi and are transported via ciliary action to pharynx to be swallowed or expectorated
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13
Q

Alveolar macrophages (dust cells)

  • Can be indicative of what disease?
  • Why?
A
  • Called HEART FAILURE CELLS IN CONGESTIVE HEART FAILURE
  • Left ventricle fails to keep pace with venous return from lungs
  • Lungs become congested with blood
  • RBCs pass into alveoli and are phagocytosed
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14
Q

In the diffusion rate equation (J), S.A. is the surface area available for diffusion
-This means that S.A. corresponds to?

A

-The number of alveoli in the lungs and the number of open pulmonary capillaries

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15
Q

As surface area increases, what happens to J?

A

As surface area increases, J (diffusion rate) increases

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16
Q

Emphysema-Caused by?

A

-Emphysema is caused by a permanent enlargement of the air spaces distal to the terminal bronchioles due to the progressive and irreversible destruction of elastic tissue of the alveolar walls

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17
Q

Emphysema

  • Elastic tissue in the interalveolar wall can be destroyed by what enzyme?
  • What type of cell releases this enzyme?
A
18
Q

Emphysema

-Elastase is neutralized by?

A

-Serum a1-antitrypsin (serum trypsin inhibitor) neutralizes elastase

19
Q

Emphysema

-So what happens in the absence of of a1-antitrypsin?

A

Neutrophil elastase is free to break down elastin, which contributes to the elasticity of the lungs, resulting in respiratory complications such as emphysema, or COPD

20
Q

Centriacinar emphysema

A
  • Dilated respiratory bronchioles at the apex of the respiratory acinus, surrounded by dilated alveolar ducts and alveoli
  • This form of emphysema is found in cigarette smokers
21
Q

Panacinar emphysema

A
  • Thin-walled air spaces of varying sizes are observed in the whole respiratory acinus
  • The boundaries of alveoli, alveolar ducts, and respiratory bronchioles are lost by coalescence after destruction of the elastic wall
  • This form of emphysema is frequent in individuals with an a1-antitrypsin deficiency
22
Q

Structural landmark of emphysema?

A

Large air spaces (blebs)

23
Q

What is mainly destroyed in centriacinar emphysema?

A

The respiratory bronchioles

24
Q

What is mainly destroyed in panacinar emphysema?

A

Respiratory bronchioles, alveolar ducts, and alveoli

25
Q

Blood-air barrier

-Refers to?

A

-Refers to the structures that O2 and CO2 must cross during gas exchange

26
Q

Blood-air barrier

-It contains?

A
  • It contains:
    • Cytoplasm of squamous epithelial cells (type I alveolar cells or pneumocytes)
    • Fused basal lamina of type I alveolar cells and capillary endothelial cells
    • Cytoplasm of capillary epithelial cell
27
Q

In the diffusion rate equation, what happens to J when distance is increased?

A

J (diffusion rate) decreases as distance (thickness of alveolar barrier) increases

28
Q

Distance includes?

A
  • Fluid layer
  • Alveolar epithelium
  • Interstitial space
  • Blood vessel wall
29
Q

Pathology of Pulmonary interstitial Fibrosis

A

The deposition of collagen within the interstitial spaces increases the diffusion distance and decreases the diffusion of the gases across the barrier

30
Q

Acute Respiratory Distress Syndrome

-A form of?

A

-A form of pulmonary edema that causes acute respiratory failure

31
Q

Acute Respiratory Distress Syndrome (ARDS)

-Results from?

A
  • Results from increased permeability of the alveolocapillary membrane
  • Results from an increase in the hydrostatic pressure in the alveolar capillaries (cardiogenic) or damage to the alveolar epithelial lining caused by bacterial endotoxins or trauma (noncardiogenic)
32
Q

Acute Respiratory Distress Syndrome (ARDS)

-What happens as a result?

A
  • Fluid accumulates in the lung interstitium, alveolar spaces, and small airways, causing the lung to stiffen
  • This stiffening impairs ventilation, prohibiting adequate oxygenation of pulmonary capillary blood
33
Q

ARDS

-Severe ARDS can cause?

A

Severe ARDS can cause intractable and fatal hypoxemia, but patients who recover may have little or no permanent lung damage

34
Q

D: Diffusion coefficient for each gas

-Depends on?

A
  • The solubility of the gas in water (in your body)
    • CO2 is much more soluble than O2
  • The molecular weight of the gas
    • CO2 weighs more than O2
35
Q

Pressure gradient

-Which gas has the larger pressure gradient-O2 or CO2?

A

O2 has the larger pressure gradient

36
Q

DL O2

-Normal value at rest??

A
  • Diffusion capacity of the lung for oxygen
  • Normal value at rest = 21 ml O2/min/mmHg
  • mmHg: avg gradient along alveolar capillary
37
Q

Measuring the DL O2

  • What gas is used? Why?
  • What is the correction factor?
A
  • Carbon monoxide is used to measure the DL O2
    • Used because it binds to Hb so avidly that it doesn’t dissolve in the plasma
  • Correction factor: DL O2 = 1.23 x DL CO
38
Q

Describe the diffusion capacity of the lung for CO2 and O2

A

How much of each gas crosses in 1 minute for every 1 mmHg gradient

39
Q

Describe how we measure the diffusion capacity for Oxygen and be able to calculate DL O2

A
  • Measured using carbon dioxide
  • To convert from DL CO to DL O2, multiply by 1.23
  • Calculates to about 21 ml O2/min/mmHg
40
Q

Pneumocyte type I

A

Squamous alveolar epithelium

41
Q

Pneumocyte type II

A

Surfactant secreting cells

42
Q

Why is surfactant important?

A
  • Surfactant changes the surface tension (T)
    • It reduces T in the smallest alveoli more than in larger alveoli to account for the change in the radius between the two different sized alveoli

CP Exam 2 (12 decks)

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