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Year 2: Human Anatomy and Physiology > RS: Ventilation > Flashcards

RS: Ventilation Flashcards

1
Q

Why does air flow into the lungs from the atmosphere?

A

Pressure gradient that is established by ‘pumps’ (thoracic cavity muscles). As volume changes, the pressure changes, and there is a flow of air (gases) into and out of the lungs to equalise the pressure change.

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2
Q

What happens to pressure when volume increases or decreases?

A

As volume increases, pressure decreases as there is a greater area in which the gas particles can move; molecules strike the walls less frequently, thus less pressure exerted.
As volume decreases, pressures increases as there is less area in which gas particles can move; molecules strike the walls more frequently, thus more pressure exerted.

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3
Q

What is inspiration?

A

Flow of air into the lungs

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4
Q

What is expiration?

A

Flow of air out of the lungs

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5
Q

Describe the pressure gradient that needs to be established for inspiration and expiration to occur within the lungs

A

For air to enter the lungs, the atmospheric pressure must be greater than the lung pressure, so air is drawn into the lungs, down its pressure gradient. This difference need only be by 1mmHg. For air to leave the lungs, the lung pressure must be greater than the atmospheric pressure, so air is forced out of lungs, down its pressure gradient.

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6
Q

What factors connect the lungs to the thoracic cavity?

A
  1. Surface tension of alveolar tends to pull them inwards, therefore pulls the whole lung inwards.
  2. Surface tension generated by surfactants lining the alveoli.
  3. Abundant elastic tissue in the lungs tends to recoil and pull the lung inwards.
    Elastic thoracic wall tends to pull away from the lungs.
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7
Q

What is the intrapleural pressure?

A

Intrapleural pressure refers to the pressure within the pleural cavity. Normally, the pressure within the pleural cavity is slightly less than the atmospheric pressure, in what is known as negative pressure.

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8
Q

Describe the changes in the intrapleural pressure of the lungs during inspiration

A

Inspiration:

  1. Diaphragm and External intercostal muscles contract.
  2. Volume of thoracic cavity increases.
  3. Interpleural pressure becomes more negative.
  4. Lungs expand.
  5. Intrapulmonary pressure becomes negative.
  6. Air flows into the lungs
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9
Q

Describe the changes in the intrapleural pressure in the lungs during expiration

A

Expiration:

  1. Diaphragm and External intercostal muscles relax.
  2. Volume of thoracic cavity decreases.
  3. Intrapleural pressure becomes less negative.
  4. Lungs recoil.
  5. Intrapulmonary pressure rises above atmospheric pressure.
  6. Air flows out of the lungs.
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10
Q

What is a pneumothorax?

A

Collapsed lung

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11
Q

What is the total pressure?

A

Total pressure is the sum of all the partial pressures of a gaseous mixture.

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12
Q

What does Dalton’s law describe?

A

Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture.

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13
Q

What does Dalton’s law of partial pressures state?

A

Dalton’s law of partial pressure states that the total pressure of a gas mixture is the sum of the partial pressures of the gas components.

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14
Q

What is the partial pressure of a gas?

A

Partial pressure is the pressure exerted by each gas in a gaseous mixture. Partial pressure of an individual gas in a mixture of gases is directly proportional to the percentage of the gas in the total gas mixture.

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15
Q

What happens to the partial pressures of individual gases at altitude?

A

At altitude, the proportion of each gas in the mixture will often stay the same, but the amount of air available will differ; reduced (total) atmospheric pressure.

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16
Q

What does Boyle’s law state?

A

States there is an inverse relationship that exists between pressure and volume: If volume increases, pressure decreases. Likewise, if volume decreases, pressure increases.

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17
Q

What is the equation that relates pressure and volume?

A

P = k/V

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18
Q

What conditions are needed for Boyle’s law to be true?

A

Law holds true only if the number of gas molecules (n) and the temperate (T) are both constant.

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19
Q

How can the relationship for Boyle’s law be expressed?

A

The relationship for Boyle’s Law can be expressed as follows: P1V1 = P2V2, where P1 and V1 are the initial pressure and volume values, and P2 and V2 are the values of the pressure and volume of the gas after change.

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20
Q

What are the muscles of inspiration?

A

External intercostal muscles

Diaphragm

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21
Q

What are the muscles of expiration?

A

Internal intercostal muscles

Abdominal muscles

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22
Q

What is the difference in muscle use during passive and forced expiration?

A

During quiet expiration, passive muscles undergo relaxation, whereas during forced expiration, internal intercostal muscles contract.

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23
Q

Describe the thoracic cavity

A

The thoracic cavity is made up of the ribs, spine and sternum, which form the tops and sides of the cavity, and a dome-shaped sheet of muscle called the diaphragm which forms the floor of the cavity.

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24
Q

Describe the basic changes during inspiration

A

Intercostal muscles and diaphragm contract, ribcage rises and lung volume increases. Pressure inside the lungs decrease to below atmospheric pressure, and air is drawn into the lungs.

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25
Q

Describe the basic changes during expiration

A

Intercostal muscles and diaphragm relax, ribcage falls and lung volume decreases. Internal intercostal muscles and abdominal muscles contract to decrease thoracic cavity volume. Pressure inside the lungs increases to above atmospheric pressure, and air is forced out of the lungs.

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26
Q

What are the 2 layers of serous membranes that surround the lungs?

A
  1. Visceral pleura

2. Parietal pleura

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27
Q

What are the pleura and what are their functions?

A

Fluid filled sacs that generate surface tension and allow the lungs to remain attached to the thoracic cavity.

28
Q

Where is the visceral pluera found?

A

Lining the lungs

29
Q

Where is the parietal pleura found?

A

Lining the inside of the thorax

30
Q

Describe the parietal cavity

A

Parietal cavity is filled with pleural fluid that provides a slippery surface to aid movement and generates surface tension to hold the lungs tight against the thoracic wall. There is always a negative pressure generated by the surface tension which acts like a suction and helps to keep the lungs inflated.

31
Q

Describe the relationship of resistance to air flow in the lungs

A

Gas molecules encounter resistance as they strike the walls of the airways. Air flow is inversely proportional to resistance; the greater the resistance, the lower the air flow.

32
Q

Describe the resistance observed in healthy lungs

A

Healthy lungs typically offer little resistance; they are compliant.

33
Q

What chemical can increase resistance in the lungs?

A

Histamine, released during an allergic reaction, causes the bronchioles to constrict which in turn increases airway resistance and decreases air flow, making it harder to breathe.

34
Q

What chemical can decrease resistance in the lungs?

A

Adrenaline, released by the adrenal medulla, causes the dilation of the bronchioles which in turn decreases airway resistance and increases air flow, making it easier to breathe.

35
Q

What is lung compliance and what determines it?

A

Lung compliance is the ease in which the lungs expand. Determined by stretchability of elastic fibres and surface tension within the alveoli.

36
Q

How is surface tension generated in the alveoli?

A

Strong attraction between water molecules at the surface of the alveolar fluid, due to Van der Waals forces, draws water molecules closer together and generates surface tension.

37
Q

What is the role of surfactant?

A

Surfactants interfere with water molecule interactions at the alveolar surface to reduce surface tension and prevent alveolar collapse; increase lung compliance.

38
Q

What is the principle surfactant produced by the lungs and where is it produced?

A

Principle surfactant produced by the lung is dipalmitoylphosphatidylcholine (DOOC) and it is synthesised in type II cells.

39
Q

What is Henry’s law?

A

The amount of gas which dissolves in a liquid is proportional to the partial pressure of the gas, and its solubility. The greater the partial pressure of the gas, the greater the number of gas molecules that will dissolve in the liquid. The concentration of the gas in a liquid is also dependent on the solubility of the gas in the liquid. For example, although nitrogen is present in the atmosphere, very little nitrogen dissolves into the blood, because the solubility of nitrogen in blood is very low.

40
Q

What is the difference between ventilation and perfusion?

A

Ventilation is the movement of air into and out of the lungs, whereas perfusion is the flow of blood in the pulmonary capillaries. For gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible.

41
Q

Describe the concentration of oxygen in the blood at equilibrium

A

At equilibrium, partial pressure of oxygen in air and water is the same, but the concentration of oxygen in solution is low, as it is poorly soluble in solution.

42
Q

Why is Hb needed for oxygen transport in the blood?

A

The poor solubility of oxygen in solution means that a carrier protein, Hb, is needed to capture and transport oxygen through the blood, so sufficient amounts of oxygen is absorbed for respiration.

43
Q

Describe the concentration of carbon dioxide in the blood at equilibrium

A

When carbon dioxide is at equilibrium at the same partial pressure, more carbon dioxide dissolves so it has a higher concentration in solution.

44
Q

What is internal respiration?

A

The exchange of gases (as oxygen and carbon dioxide) between the cells of the body and the blood by way of the fluid bathing the cells

45
Q

What is external respiration?

A

The exchange of gases between the external environment and a distributing system of the animal body (such as the lungs of higher vertebrates or the tracheal tubes of insects) or between the alveoli of the lungs and the blood.

46
Q

What factors influence internal respiration?

A
  1. Available surface area (varies between tissues)
  2. Partial pressure gradients
  3. Rate of blood flow
47
Q

What factors influence external respiration?

A
  1. Surface area and structure of the respiratory membrane.
  2. Partial pressure gradients.
  3. Matching alveolar air flow to pulmonary capillary blood flow
48
Q

Why do the partial pressures of the gases inhaled differ to those in the atmosphere?

A
  1. Humidification of the inhaled air that absorbs some oxygen
  2. Continuous gas exchange between the alveoli and capillaries
  3. Mixing of old and new air as alveoli do not completely empty between breaths.
49
Q

How does ventilation perfusion coupling help maximise efficient gas exchange?

A

Helps maintain proportionate alveoli air flow to pulmonary capillary blood flow

50
Q

How is blood flow regulated in line with air flow and partial pressure of gases within the blood?

A

Regions with high airflow to blood supply will have blood with high partial pressure of oxygen. Arteriolar vasodilation to increase blood flow to take up abundant oxygen.

Regions with low airflow to blood supply will have blood with a low partial pressure of oxygen. Arteriolar vasoconstriction to cause blood to be redirected to the alveoli, where air flow and oxygen availability is greater.

51
Q

What is the percentage of oxygen dissolved in blood?

A

Roughly 1.5%

52
Q

What is the percentage of oxygen bound to haemoglobin?

A

Roughly 98.5%

53
Q

Describe the structure of haemoglobin

A

Hb is composed of 4 protein globin chains, and each chain has a heme group at its centre. Each heme group consists of a polymorphic ring with an iron atom in the centre, each of which can bind reversibly to one molecule of oxygen.

54
Q

How many oxygen molecules can each haemoglobin molecule bind to?

A

4 molecules of oxygen

55
Q

What is haemoglobin co-operativity?

A

Oxygen binding increases the affinity of hemoglobin for more oxygen. Increased affinity is caused by a conformational change, or a structural change in the hemoglobin molecule from a tensed (T) state to a relaxed (R) state. Hb affinity for oxygen increases as saturation increases.

56
Q

Describe the relationship between the availability of oxygen and the binding of haemoglobin

A

The more oxygen available, the more rapid the association of oxygen to haemoglobin and the less oxygen available, the more rapid the dissociation of oxygen from haemoglobin. Oxygen is more likely to associate with Hb in an environment with high conc., ie the lungs, and is more likely to dissociate from Hb in an environment with low conc. ie respiring tissue/cells.

57
Q

What is the utilisation coefficient?

A

The amount of oxygen, in the blood, that has been dissociated and given up to the respiring cells.

Hb- oxygen saturation is around 98% as oxygen arrives at the systemic circulation and is around 75% as it leaves the capillaries of the resting tissues; Hb has given up roughly 23% of its oxygen.

58
Q

What is the venous reserve?

A

The remaining oxygen in the blood, after donation to the respiring tissue.

59
Q

What is significant about the venous reserve?

A

It can be used to sustain life for 4-5 minutes in the event of a respiratory arrest.

60
Q

What are the 5 factors affecting oxygen-Hb dissociation?

A
  1. Oxygen concentration (because of cooperativity)
  2. Body temperature
  3. Carbon dioxide concentration
  4. Plasma pH (Bohr Effect)
  5. 2,3 BPG
61
Q

What is the effect of carbon dioxide concentration of oxygen-Hb dissociation?

A

Increasing carbon dioxide concentration shifts the dissociation curve to the right as more Hb is more likely to donates its oxygen molecules due to low oxygen environment.

62
Q

What is the effect of body temperature of oxygen-Hb dissociation?

A

Increasing body temperature shifts the dissociation curve to the right as more oxygen is capable of dissociating.

63
Q

What is the effect of plasma pH (Bohr Effect) on oxygen-Hb dissociation?

A

Decreasing pH, increasing acidity, shifts the dissociation curve to the right because hydrogen ions cause Hb to undergo a conformational change which decreases its affinity for oxygen so is more likely to dissociate its oxygen.

64
Q

What is the effect of 2,3 BPG on oxygen-Hb dissociation?

A

RBCs generate their own energy through a form of fermentation, and the by-product of such process is 2,3 BPG. Oxygenated Hb inhibits the enzyme responsible for 2,3 BPG synthesis. Chronic hypoxia increases 2,3 BPG levels and lowers Hb affinity for oxygen; dissociation curve shifts to the right and oxygen is more readily given up.

65
Q

What is the Haldane effect?

A

Hb can transport carbon dioxide and oxygen simultaneously, but the binding of one tends to inhibit the binding of the other.

Year 2: Human Anatomy and Physiology (18 decks)

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