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Biology > 6.4 Gas exchange > Flashcards

6.4 Gas exchange Flashcards

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1
Q

What does ventilation maintain?

A

Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries

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2
Q

What is gas exchange?

A

The process in which organisms absorb one gas from the environment and release a different one

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3
Q

How do humans use gas exchange?

A

Human absorb oxygen for use in cell respiration and release the carbon dioxide produced by this process

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4
Q

Where do gas exchange occur in humans and in terrestrial organisms?

A

Humans: In small air sacs called alveoli inside the lungs
Terrestrial organisms: exchange gases with the air

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5
Q

How does gas exchange happen by?

A

By diffusion between air in the alveoli and blood flowing in the adjacent capillaries

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6
Q

How does the gases only diffuse during gas exchange?

A

The gases only diffuse because there is a concentration gradient

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7
Q

Describe the concentration gradient involving the alveolus and the blood in the capillary?

A

The air in the alveolus
* higher conc. of oxygen
* Lower conc. of CO2
… compared to the blood in the capillary

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8
Q

How do humans maintain the concentration gradient between oxygen and CO2?

A
  • Fresh air must be pumped into the alveoli
  • Stale air must be removed
    This process is called ventilation
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9
Q

What is the process of maintaining the concentration between oxygen and Co2 called?

A

Ventilation

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10
Q

What are type I pneumocytes?

A

extremely thin alveolar cells that are adpated to carry out gas exchange

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11
Q

What does the lung contain huge numbers of?

A

Alveoli

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12
Q

What is the purpose of having huge numbers of alveoli in the lungs?

A

For a very large total surface area for diffusion. Diffusion for gas exchange

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13
Q

What is the wall of each alveolus consist of?

A

A thin layer of cells, called the epithelium

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14
Q

What type are most of the cells in the epithelium of each alveolus?

A

Type I pneumocytes

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15
Q

What do type I pneumocytes look like?

A

Flattened cells, with the thickness of only about 0.15 micrometer

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16
Q

What do the walls of the adjacent capillaries also consist of?

A

A single layer of very thin cells
Therefore the air in the alveolus and the blood in the alveolar capillaries are less than 0.5 micrometer apart

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17
Q

How does the distance between the air in the alveolus and the blood in the alveolar capillaries affect gas exchange?

A

The distance over which oxygen and carbon dioide has to diffuse is therefore very small, which is an adaptation to increase the rate of gas exchange

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18
Q

What is the adaptation of having a thin layer of cells as the wall for alveolus and capilliaries?

A

Short diffusion pathways -> increase the rate of gas exchange

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19
Q

What are type II pneumocytes?

A

Rounded cells that occupy about 5% of the alveolar surface area

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20
Q

What do type II pneumocytes secrete?

A

A solution containing surfactant that coats the inner surface of the alveoli

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21
Q

What does the film of moisture from the solution secreted by type II pneumocytes allow for?

A
  • Allows oxygen in the alveolus to dissolve and then diffuse to the blood in the alveolar capillaries
  • It also provides an area from which carbon dioxide can evaporate into the air and be exhaled
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22
Q

What does the fluid secreted by the type II pneumocyte contain?

A

A pulmonary surfactant

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23
Q

What is similar of the molecules in the pulmonary surfactant and phospholipids?

A

Its molecules have a similar structure with phospholipids in cell membranes .

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24
Q

What does the pulmonary surfactant do?

A

It forms a monolayer on the surface of the moisture lining the alveoli, with the hydrophilic heads facing the water and the hydrophobic tails facing the air.

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25
Q

How does surfactant prevent the collapse of the lung?

A
  • reduces the surface tension and prevents the water from causing the sides of the alveoli to adhere when air is exhaled from the lungs
  • due to the hydrophilic tails
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26
Q

How is the pulmonary surfactant positioned to stop the sides of the alveoli to adhere when air is exhaled from the lung?

A

The hydrophilic heads facing the water and hydrophobic tails facing the air.

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27
Q

What do premature babies suffer from when they are born without insufficient pulmonary surfactant?

A

Infant respiratory distress syndrome

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28
Q

How is infant respiratory distress syndrome treated?

A
  • giving the baby oxygen
  • one or more doses of surfactant, extracted from animal lungs
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29
Q

Where does air enter the ventilation system?

A

through the nose or mouth, then passes down the trachea

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30
Q

What does the rings of cartilage do in the trachea?

A

To keep it open even when air pressure inside is low or pressure in surrounding tissues is high

31
Q

What does the trachea divide to form?

A

Two bronchi, with walls strengthened with cartilage

32
Q

What does one bronchus lead to?

A

each lung

33
Q

Inside the lung, what do the bronchi do?

A

They divide repeatedly to form a tree-like strucutre of narrower airways, called bronchioles.

34
Q

What do bronchioles have in their walls?

A

Smooth muscle fibres, allowing the width of these airways to vary

35
Q

What is found at the end of the narrowest bronchioles?

A

A group of alveoli, where gas exchange occurs

36
Q

What happens to the pressure when the volume increases or decreases?

A

Increase volume = decrease pressure
Decreased volume = increased pressure

37
Q

If a gas is free to move, where will it flow from and to?

A

It will always flow from regions of higher pressure to regions of lower pressure

38
Q

During ventilation, what causes the pressure inside the thorax to drop below atmospheric pressure?

A

Muscle contractions

39
Q

What is the consequence of muscle contractions during ventilation?

A

The contraction of respiratory muscles changes the volume of the thoracic cavity (i.e. the chest)

40
Q

What happens when the volume of the thoracic cavity increases and decreases?

A

Increase = pressure in the thorax decreases
Decrease = pressure in the thorax increases

41
Q

What effect does muscle contractions have during expiration?

A

They cause the pressure inside the thorax to rise above atmospheric, so air is forced out from the lungs to the atmosphere

When the pressure in the chest is greater than the atmospheric pressure, air will move out of the lungs (expiration)

42
Q

What effect does muscle contractions have during inspiration?

A

Cause the pressure inside the thorax to drop below atmpspheric pressure and air is drawn into the lungs from the atmosphere

When the pressure in the chest is greater than the atmospheric pressure, air will move out of the lungs (expiration)

43
Q

What effect does muscle contractions have during inspiration?

A

Cause the pressure inside the thorax to drop below atmpspheric pressure and air is drawn into the lungs from the atmosphere

When the pressure in the chest is greater than the atmospheric pressure, air will move out of the lungs (expiration)

44
Q

Compare the pressure during inspiration and expiration?

A
  • When the pressure in the chest is less than the atmospheric pressure, air will move into the lungs (inspiration)
  • When the pressure in the chest is greater than the atmospheric pressure, air will move out of the lungs (expiration)
45
Q

What two states can muscles be in?

A

Contracting and relaxing

46
Q

How do muscles do work?

A

When they contract by exerting a pulling force (tension) that causes a particular movement. They become shorter when they do this

47
Q

What happens to muscles when they are relaxing?

A

Muscles lengthen passively when relaxing - they do not lengthen themselves.
* Most muscles are pulled into an elongated state by the contraction of another muscle - they do no exert a pushing force (compression) while relaxing

48
Q

Why can muscles only cause movement in one direction?

A

Because the opposite movement is required by a second muscle contracting while the other one relaxes.

49
Q

if movement in opposite directions is needed at different times, what is needed?

A

Two muscles will be required

50
Q

What is an antagonistic pair of muscles?

A

When muscles work together for two opposite movements.
* When one muscle contracts and causes a moement, the second muscle relaxes and is elongated by the first.
* The opposite movement is caused by the second muscle contracting while the first relaxes.

51
Q

How are antagonistic pair of muscles related to gas exchange?

A

Inspiration and expiration involve opposite movements, so different muscles are required, working as antagonistic pairs

52
Q

What are the examples of antagonisitic muscle action in ventilation?

A
  • External and internal intercoastal muscles
  • Diaphram and abdominal muscles
53
Q

What do ventilation need two pairs of opposite movements for?

A

to change the volume. andtherefore the pressure inside the thorax

54
Q

What happens to the diaphram and ribcage during inspiration and expiration?

A
55
Q

How does volume and pressure change during inspiration and expiration?

A
56
Q

How does the diaphragm and abdomen wall muscles influence the movement of the diaghragm during inspiration and expiration?

A
inspiration on left column and expiration on the right
57
Q

How does the external and internal intercostal muscles influence the movement of the ribcage during inspiration and expiration?

A
inspiration on the left column and expiration on the right
58
Q

What does tobacco smoke contain lots of?

A

Mutagenic chemicals

59
Q

How does passive smoking cause 3% of lung cancer cases?

A

This happens when non-smokers inhale tobacco smoke exhaled by smokers

60
Q

How does air pollution probably cause about 5% of lung cancers?

A

The sources of air pollution that are most significant are diesel exhaust fumes, nitrogen oxides from all vehicles exhaust fumes and smoke from bruning coal, wood or other organic matter

61
Q

How does Radon gas cause significant number of cases?

A

Radon gas is a radioactive gas that leaks out of certain rocks such as granite.
It accumulates in badly ventilated buildings and people then inhale it

62
Q

How does Asbestos, silica and some other solid cause lung cancer?

A

If dust or other particles of them are inhaled. This usually happens on construction sites or in quarries, mines or factories

63
Q

What are some symptoms of lung cancer?

A
  • difficulties with breathing
  • persistent coughing
  • coughing up blood
  • chest pain
  • loss of appetite
  • weight loss
  • general fatigue
64
Q

What is emphysema?

A

a lung condition whereby the walls of the alveoli lose their elasticity due to damage to the alveolar walls

65
Q

How does the alveoli of emphysema patients compare to a healthy lung?

A
  • Smaller number of larger air sacs with much thicker walls
  • Huge air space (pulmonary bullae)
  • total surface area for gas exchange is considerably reduced
  • Distance over which diffusion of gases occurs is increased

= gas exchange is much less effective
= lung is less elastic, so ventilation is more difficult

66
Q

What happens when a lung is less elastic?

A

Ventilation is more difficult

67
Q

What do phagocytes ustually do inside aleveoli?

A

normally prevent lung infections by:
* engulfing bacteria
* producing elastase, a protein-digesting enzyme, to kill them inside the vesicles formed by endocytosis

68
Q

What prevents elastase and other proteases form digesting lung tissue?

A

An enzyme inhibitor called alpha 1-antitrypsin (A1AT)
* Elastase activity can be blocked by an enzyme inhibitor (α-1-antitrypsin), but not when elastase concentrations are increased

69
Q

What would you expect of the phagocytes in smokers?

A

The number of phagocytes in the lungd increases and they try to produce more elastase

70
Q

How does smoking cause damage to alveolar walls

A

The damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase
This elastase, released as part of an inflammatory response, also breaks down the elastic fibres in the alveolar wall

71
Q

How does smoking cause damage to alveolar walls

A

The damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase
This elastase, released as part of an inflammatory response, also breaks down the elastic fibres in the alveolar wall

72
Q

How does genetic factors play a role in emphysema?

A
  • affect the quantity and effectiveness of A1AT produced in the lungs
73
Q

Why is emphysema a chronic disease?

A

The damage to alveoli is usually irreversible
* It causes low oxygen saturation in the blood and higher than normal carbon dioxide concentrations.

74
Q

What explains an emphysema patients lack o energy?

A

Low oxygen saturation in the blood and higher than normal CO2 conc.
* Ventiation is laboured and tends to be more rapid than normal

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