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IB HL Biology > 6.4 Gas exchange > Flashcards

6.4 Gas exchange Flashcards

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1
Q

Diagram of the human lungs

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2
Q

Diagram of gas exchange in an alveolus

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3
Q

What is ventilation?

A

As you breathe in air and quickly breathe out again, you are bringing fresh air into your alveoli and removing the stale air – this process is called ventilation.

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4
Q

How does the breathing rate change when someone runs?

A

Normally in an adult, the breathing rate is between 12–20 times per minute, but that can increase to 30–40 times per minute when you are running at full speed.

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5
Q

What is the purpose of ventilation?

A
  • Ventilation maintains concentration gradients of oxygen and carbon dioxide between the air in alveoli and blood flowing in adjacent capillaries.
  • The longer air remains in the alveoli, the lower the concentration of oxygen in that air, thus decreasing the concentration gradient that drives the diffusion of oxygen into the blood.
  • Ventilation removes this lower oxygen air and replaces it with fresh, higher oxygen air.
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6
Q

Why is it essential for ventilation to remove this lower-oxygen air and replace it with fresh, higher-oxygen air?

A

This is essential to ensure that oxygen continuously diffuses into the blood from the alveoli and carbon dioxide diffuses out of the blood into the alveoli.

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7
Q

The exchange of gases that occurs at the alveoli is called ___ and is directly dependent on ___.

A

Gas exchange

Ventilation

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8
Q

Table showing the percentages of each gas in inhaled and exhaled air

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9
Q

Define ventilation rate/breathing rate

A

The number of breaths, including inhalation and exhalation, taken per minute.

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10
Q

Diagram showing the relationship between the lungs, the bronchi, the bronchioles, and the alveoli

A
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11
Q

What are the two concentration gradients that gas exchange depends on?

A

One gradient of oxygen, and another gradient of carbon dioxide.

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12
Q

What are the alveoli?

A

The tiny air sacs of the lungs where gaseous exchange takes place.

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13
Q

Describe the oxygen and carbon dioxide concentrations in the alveoli

A
  • In the alveoli, the oxygen concentration is higher than the concentration of oxygen in the blood that flows past the alveoli.
  • The opposite is true for carbon dioxide, which is present in higher concentrations in the blood and lower concentrations in the freshly inhaled air in the alveoli.
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14
Q

Why is the gradient of O2 and CO2 in the alveoli important?

A

This gradient, as well as the thin walls and moisture of the alveoli and the short distance to the capillaries, facilitates gas exchange by diffusion.

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15
Q

Diagram of an alveolus

A
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16
Q

The wall of an alveolus is made up of ___.

A

Two types of alveolar cells.

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17
Q

What are the two types of alveolar cells that the wall of an alveolus is made up of?

A
  • Type I pneumocytes
  • Type II pneumocytes
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18
Q

Describe the structure of type I pneumocytes and how this relates to their function

A
  • They are extremely thin alveolar cells that are adapted to carry out gas exchange.
  • They are very flat and thin, increasing the surface area available for diffusion.
  • This also speeds up diffusion by decreasing the distance between the inside of the alveolus and the capillary.
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19
Q

Describe the structure of type II pneumocytes and how this relates to their function

A
  • These secrete a solution containing surfactant, which is a water-based solution containing phospho-lipoproteins.
  • Surfactants create a moist surface inside the alveoli to prevent the sides of the alveoli from sticking to each other: they do this by reducing surface tension.
  • The moisture also increases the speed gases dissolve, which helps gas exchange.
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20
Q

In humans, gas exchange between the atmosphere and the pulmonary blood occurs in the ___

A

Alveoli

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21
Q

Define ventilation

A

Muscle movement to move fresh air into alveoli

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22
Q

Define gas exchange

A

Replacing carbon dioxide with oxygen in the blood in lungs

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23
Q

What cellular process is required for gas exchange to occur?

A

Diffusion

Gas exchange relies on concentration gradients created by ventilation and the movement of blood through capillaries. Gases diffuse passively based on these gradients.

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24
Q

What is the function of type I pneumocytes in the alveoli?

A

Perform gas exchange

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25
Q

How many steps does ventilation consist of?

A

Two

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26
Q

What are the two steps that ventilation consists of?

A
  • Inspiration (breathing in) and expiration (breathing out).
  • Sometimes these two steps are called inhalation and exhalation, respectively.
27
Q

Describe how air works because it is a gas

A
  • Air is a gas and obeys physical laws, called gas laws.
  • The pressure of a gas is directly related to the number of molecules that occupy a certain volume: when the volume is larger the pressure is lower.
  • The flow of gas is always from an area of high pressure to an area of low pressure.
28
Q

What happens when a gas is compressed and when it expands?

A
  • When a gas is compressed (its volume decreases), its pressure rises.
  • The opposite is also true: when a gas expands, its pressure decreases.
  • That is what happens in the lungs.
29
Q

Explain how pressure changes in the lungs during inhalation

A
  • When breathing in, the thorax (the chest) expands and the pressure inside the lungs is lowered, ensuring that thoracic pressure is lower than atmospheric pressure.
  • This causes air to rush into the lungs.
30
Q

Explain how pressure changes in the lungs during exhalation

A

When we breathe out, the thorax gets smaller, the pressure rises and the air is forced out of the lungs.

31
Q

Describe the pathway air follows to get to the alveoli

A
  • Air is carried to the lungs through the trachea and bronchi and then to the alveoli in the bronchioles.
  • This is the pathway air follows during ventilation: mouth/nasal passage ↔ trachea ↔ two bronchi (one for each lung) ↔ bronchioles ↔ alveoli.
32
Q

Diagram showing what happens during inspiration (inhalation)

A
33
Q

Diagram showing what happens during expiration (exhalation)

A
34
Q

Describe what happens during inspiration (inhalation)

A
  • External intercostal muscles contract
  • Internal intercostal muscles relax
  • Diaphragm contracts (drops)
  • Abdominal muscles relax
  • Pressure in the lungs decreases while volume increases.
  • Air enters.

(Rib cage expands as rib muscles contract)

35
Q

Describe what happens during expiration (exhalation)

A
  • Internal intercostal muscles contract
  • External intercostal muscles relax
  • Diaphragm relaxes (rises)
  • Abdominal muscles contract
  • Pressure in the lungs increases while volume decreases.
  • Air escapes.

(Muscle contraction makes rib cage smaller)

36
Q

Why are different muscles required for inspiration and expiration?

A

Because muscles only do work when they contract.

37
Q

Diagram showing the muscles involved in inspiration and expiration

A
38
Q

Describe the difference between internal and external intercostal muscles

A

Muscles involved in inspiration and expiration

39
Q

What happens to move the ribs back down and in?

A

The internal intercostals contract

40
Q

When do muscles only work?

A

When they contract: the external intercostals can only lift the ribs, and the internal intercostals can only move ribs down.

41
Q

What are antagonistic muscles?

A

Muscles that work in pairs to move body parts in opposite directions.

42
Q

What kind of muscles are external and internal intercostal muscles?

A

Antagonistic

43
Q

What kind of muscles are the diaphragm and certain abdominal muscles and why?

A

Antagonistic: the diaphragm contracts to increase the volume of the thorax, but other abdominal muscles must contract to move the diaphragm back up during exhalation.

44
Q

Method to remember the muscles involved in inspiration and expiration

A

To help you remember, the muscles involved begin with the opposite letters to the action:

  • In spire: external intercostal muscles.
  • Ex pire: internal intercostal muscles.
45
Q

Define tidal volume

A
  • The volume of air that enters or leaves the lungs in a single breath at rest.
  • The average tidal volume is 500 ml.
46
Q

Overview of experiment to measure ventilation in humans

A
  • Depending on the resources available in your school laboratory this practical can involve monitoring ventilation either by simple observation (counting breaths per minute) or a simple apparatus (exhaling into an apparatus that can measure volume by water displacement).
  • If available, you might take measurements by data logging with a spirometer or chest belt and pressure meter.
  • You could measure ventilation rate or tidal volume.
47
Q

What data can be collected in an experiment to measure ventilation in humans?

A
  • Throughout this practical, you will collect data on the ventilation of individuals when at rest and after exercising for different periods of time.
  • Depending on your sample size, these data can then be processed to see if there is any relationship between ventilation rate or tidal volume and other variables you may have investigated, such as:
  • The amount of time that the subject has been exercising
  • Gender or age (this relationship can only be established if the group of individuals for each gender and age group is large).
48
Q

Air rushes into the lungs of humans during inspiration because ___

A

The external intercostal muscles and diaphragm contract, increasing the lung volume.

49
Q

The expiration of air from human lungs is driven by ___

A

A decrease in the volume of the thoracic cavity.

During expiration, internal intercostal muscles contract, while the diaphragm relaxes. This decreases the volume of the thoracic cavity and causes the internal pressure to rise. As a result, air is expelled.

50
Q

During which stage of ventilation is the diaphragm contracted?

A

Inspiration/inhalation

51
Q

Global smoking statistics

A
  • Globally, 12% of all deaths among adults aged 30 years and over are due to tobacco.
  • The proportion of deaths due to tobacco is higher among men than among women.
  • Tobacco use is responsible for 10% of all deaths from cardiovascular diseases, 22% of all cancer deaths, and 36% of all deaths from diseases of the respiratory system.
52
Q

Give an overview of the history of the tobacco industry and its acknowledgement of the dangers of smoking

A
  • It took a long time and many legal battles before the tobacco industry finally admitted that there was a link between smoking and cancer, emphysema, and cardiovascular diseases.
  • Initially, research established a link between cigarette use and lung cancer.
  • Later, large-scale studies revealed a strong correlation. In laboratory tests, a causal relationship was established between the compounds in cigarette smoke and many different types of cancer.
53
Q

What is epidemiology?

A
  • The study of the incidence and cause of a disease.
  • It uses statistics to establish correlations, which may then trigger research to look into causal relationships.
54
Q

What is the most common form of cancer?

A

Lung cancer

55
Q

Describe how easy or difficult lung cancer is to treat and its mortality rate

A

There are several types of lung cancer, but all are difficult to treat and have a high mortality (death) rate.

56
Q

What percent of lung cancers are caused by smoking?

A

87%

57
Q

List some of the causes of lung cancer

A
  • Asbestos dust particles lodge in the lungs and cannot be broken down
  • Smoking (cigarettes, cigars, pipe tobacco)
  • Passive smoking (breathing in someone else’s cigarette smoke); about 3% of all cases
  • Air pollution: diesel exhaust fumes contain many carcinogens (compounds causing cancer)
  • Radon gas: in some parts of the world there is a higher concentration of this radioactive gas. It emits alpha particles, which can cause mutations when inhaled.
58
Q

List some of the possible consequences of lung cancer

A
  • Shortness of breath
  • Cough that does not go away
  • Coughing up blood
  • Pain (chest pain and pain in other areas if cancer spreads)
  • Accumulation of fluid in the chest
  • Spread of cancer to other parts of the body
  • Loss of appetite or weight loss
  • Fatigue
  • Repeated problems with pneumonia or bronchitis
59
Q

What is emphysema caused by?

A

Long-term exposure to cigarette smoke and other pollutants.

60
Q

What does emphysema lead to?

A
  • An inflammatory (swelling of tissues) response in the lungs, resulting in a narrowing of the small airways and breakdown of lung tissue.
  • There is also evidence that the alveoli become less elastic, making ventilation more difficult.
  • Furthermore, there is increased protease activity, which breaks down the alveolar wall, creating one larger air space instead of many small ones.
  • This reduces the surface area of the lungs and results in a smaller amount of oxygen reaching the bloodstream.
61
Q

How does emphysema affect the inhibition of alpha-1-antitrypsin?

A

Normally, the proteases are inhibited by alpha-1-antitrypsin, but in emphysema patients, the activity of this enzyme inhibitor is reduced.

62
Q

Are the effects of emphysema reversible or irreversible processes?

A
  • These are all irreversible processes, resulting in a reduction of the oxygen saturation of the blood because gas exchange can no longer occur in the damaged alveoli.
  • Patients with emphysema are always short of breath and cough frequently.
  • In cases of severe emphysema, some patients may benefit from oxygen therapy or even a lung transplant.
63
Q

What are the possible consequences of emphysema?

A
  • Shortness of breath
  • Persistent cough
  • Fatigue
  • Weight loss
  • Depression.
64
Q

Which process does emphysema make more difficult?

A

Both ventilation and gas exchange

IB HL Biology (68 decks)

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