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BDS1 BAMS: Respiratory System > Respiratory Gas Exchange > Flashcards

Respiratory Gas Exchange Flashcards

1
Q

What process do gases move down their concentration gradients?

A

Diffusion

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2
Q

What is partial pressure?

A

The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own

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3
Q

Sum of the partial pressures or tensions of a gas must be equal what?

A

Total pressure

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4
Q

What is atmospheric pressure (at sea level)?

A

760 mmHg (barometric pressure)

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5
Q

How do you calculate the partial pressure of a gas?

A

Partial pressure of gas (Pgas) = Fraction of gas (Fgas) in mixture x barometric pressure

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6
Q

Oxygen makes up 21% of the total gases in air. What is the partial pressure of oxygen at the mouth?

A

PO2 = 0.21 x 760 = 159 mmHg (at mouth)

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7
Q

What is the water vapour partial pressure at body temperature?

A

47 mmHg

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8
Q

Oxygen makes up 21% of total gases in the air. What is the partial pressure of oxygen in the trachea? (water vapour partial pressure at body temp = 47 mmHg)

A

PO2 = 0.21 x (760-47) = 150 mmHg in trachea

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9
Q

Describe the pattern of branching in the respiratory tree

A

Airways branch into smaller and more numerous bronchioles before terminating to a group of alveoli.
Each division results in an increase in number, a decrease in diameter, and an increase in surface area

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10
Q

What are the components of the conducting airways?

A

Bronchi containing cartilage and non-respiratory bronchioles
Everything from the trachea to the bronchioles
Does not participate in gas exchange

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11
Q

What is ‘anatomic dead space’?

A

The total volume of the conducting airways from the nose/mouth to the level of the terminal bronchioles. Fills with inspired air at the end of each inspiration but is exhaled unchanged. Does not participate in gas exchange.

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12
Q

What volume of air is in the conducting airways?

A

150ml (30% of average breath)

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13
Q

What are the respiratory airways?

A

Bronchioles with alveoli where gas exchange occurs (from terminal bronchioles to alveoli)

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14
Q

What volume of air is held in the respiratory airways?

A

~2,500ml

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15
Q

What is the respiratory unit?

A

The basic physiological unit of the lung consisting of respiratory bronchioles, alveolar ducts and alveoli

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16
Q

How many alveolar sacs are present in an adult?

A

~300-400 million

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17
Q

What shape are alveoli?

A

Polygonal

18
Q

What is the diameter of an alveoli?

A

~250 micrometres

19
Q

What types of epithelial cells are found in alveoli?

A

Type 1 and type 2 epithelial cells

20
Q

Which type of epithelial cells occupy 97% of surface area of alveoli?

A

Type 1 epithelial cells

21
Q

Which epithelial cells are the primary site of gas exchange?

A

Type 1 epithelial cells

22
Q

Which type of epithelial cell occupies 3% of surface area of alveoli?

A

Type 2 epithelial cells

23
Q

What do type 2 epithelial cells do?

A

Produce pulmonary surfactant - reduces surface tension

24
Q

What does surfactant allow the lung to do?

A

Important for normal lung function

Allows lung to expand and have elastic properties

25
Q

What is often the cause of death in premature babies ~23 weeks?

A

Lungs are unable to produce surfactant
Breathing is very laboured, lungs can’t expand
Epithelial lining can get irritated and come away from the lung

26
Q

What is the function of alveolar macrophages?

A

Removal of debris

27
Q

Which characteristics make alveoli perfectly designed for gas exchange?

A
  • Large surface area (100m^2)
  • Very thin walls (0.5 micrometers)
  • Good diffusion characteristics
28
Q

The lung has 2 separate blood supplies. What are these termed?

A

Pulmonary circulation

Bronchial circulation

29
Q

Describe the pulmonary circulation

A

Brings deoxygenated blood from the heart to the lungs and oxygenated blood from the lungs to the heart, and then rest of the body
Pulmonary artery brings deoxygenated blood to lungs, pulmonary vein carries oxygenated blood to heart

30
Q

Describe the bronchial circulation

A

Bronchial circulation is part of the systemic circulation carrying oxygenated blood to support the tissues of the lungs
Not to do with gas exchange

31
Q

What is the total blood volume in the pulmonary circulation?

A

500ml (10% total)

32
Q

How much blood is in the alveolar-capillary network at rest?

A

75ml

33
Q

During exercise, how much blood is in the alveolar-capillary network?

A

150-200ml

Involves recruitment of new capillaries secondary to an increase in pressure and flow

34
Q

Describe arteries in the alveolar capillary network

A

Thin walled, highly compliant, large diameter, low resistance (compared to systemic circulation)

35
Q

Where does gas exchange occur?

A

Respiratory airways

Through dense mesh-like network of capillaries and alveoli

36
Q

What is the distance between alveoli and red blood cells, and what is the distance composed of?

A

1-2 micrometres: type 1 alveolar epithelial cell, capillary endothelial cell and basement membrane

37
Q

How long does it take for a RBC to pass through capillaries?

A

Less than 1 second

Sufficient time for CO2 and O2 in gas exchange

38
Q

Describe the movement of oxygen in the pulmonary circuit in terms of pressure gradients

A

Oxygen moves from an area of high concentration (100 mmHg) in alveoli to an area of low concentration (40 mmHg) in blood vessel

39
Q

Describe the movement of carbon dioxide in the pulmonary circuit in terms of pressure gradients

A

Carbon dioxide moves from an area of high (45 mmHg) concentration in the blood vessel to an area of low (40 mmHg) concentration in the alveolar sac

40
Q

Similar volumes of oxygen and carbon dioxide move each minute. Why is the pressure gradient for oxygen much bigger than that of carbon dioxide?

A

Carbon dioxide is more diffusible

41
Q

Pulmonary circulation carries large volumes of blood at ___ pressures

A

Low

42
Q

Pulmonary circulation brings ____________ blood from right ventricle to alveolar-capillary network where gas exchange occurs

A

Deoxygenated

BDS1 BAMS: Respiratory System (8 decks)

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