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Medicine 1 - Physiology > Anatomy of Pleural Cavity, Mechanics of Breathing, Surfactant and Compliance > Flashcards

Anatomy of Pleural Cavity, Mechanics of Breathing, Surfactant and Compliance Flashcards

1
Q

Tidal Volume (TV)

A

The volume of air breathed in and out of the lungs at each breath

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2
Q

Expiratory Reserve Volume (ERV)

A

The maximum volume of air which can be expelled from the lungs at the end of a normal expiration.

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3
Q

Inspiratory Reserve Volume (IRV)

A

The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration.

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4
Q

Residual Volume (RV)

A

The volume of gas in the lungs at the end of a maximal expiration.

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5
Q

Vital Capacity (VC)

A

The greatest volume of air that can be expelled from the lungs after taking the deepest possible breath.

Tidal volume + inspiratory reserve volume + expiratory reserve volume

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6
Q

Total Lung Capacity (TLC)

A

The volume in the lungs at maximal inflation

Vital capacity + residual volume

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7
Q

Inspiratory Capacity (IC)

A

The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration.

Tidal volume + inspiratory reserve volume

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8
Q

Functional Residual Capacity

A

The volume remaining in the lungs after a normal, passive exhalation.

In a healthy individual, this is about 3L.

Expiratory reserve volume + residual volume

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9
Q

FEV1:FVC

A

How much air can be forcefully exhaled in one second

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10
Q

What is the pleural cavity?

A

The space enclosed by the pleura

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11
Q

How many pleural cavities are there and what are they made up of?

A

Two - one around each lung

Made up of:

Parietal pleura
Visceral pleura

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12
Q

What is the parietal pleura?

A

The outer pleura that is attached to the chest wall

Stuck to deep surface of chest wall

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13
Q

What is the visceral pleura?

A

Covers the outer surface of the lungs, and extends into the interlobar fissures

Stuck to superficial lung surface

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14
Q

What is the visceral pleura in line with?

A

Helium of lung

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15
Q

What do the pleura consist of?

A

They consist of a serous membrane – a layer of simple squamous cells supported by connective tissue.

This is also called the mesothelium.

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16
Q

What can the parietal pleura further be divided up into?

A

Mediastinal pleura
Cervical pleura
Costal pleura
Diaphragmatic pleura

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17
Q

What does the mediastinal pleura cover?

A

Lateral aspect of mediastinum

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18
Q

What does the cervical pleura cover?

A

Extension of the pleural cavity into the neck

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19
Q

What does the costal pleura cover?

A

Inner aspect of ribs, costal cartilages and intercostal muscles

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20
Q

What does the diaphragmatic pleura cover?

A

Thoracic (superior) surface of the diaphragm

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21
Q

How can the pleural cavity be described?

A

As a potential spacebetween the parietal and visceral pleura

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22
Q

What can be found inside the pleural cavity?

A

A small volume of serous fluid called pleural fluid

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23
Q

What does plural fluid do?

A

It lubricates the surfaces of the pleurae, allowing them to slide over each other.

Produces a surface tension, pulling the parietal and visceral pleura together. This ensures that when the thorax expands, the lung also expands, filling with air.

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24
Q

What is it called when air enters the pleural cavity?

A

Pneumothorax - surface tension lost

25
Q

What happens when air enters the pleural cavity?

A

Pleural membranes separate because the air forces it apart

Nothing to stop the lung recoiling and chest wall expanding and the lungs recoil away from the chest wall.

It doesn’t matter what the chest wall muscles do as the lungs will no longer follow.

26
Q

What does elastic recoil allow?

A

Rebound of the lungs after having been stretched by inhalation

27
Q

What can cause a pneuomothorax?

A

Chest being stabbed

28
Q

What brings about recoil of chest wall in normal expiration?

A

Recoil of the elastic connective tissues

29
Q

What is the main muscle of breathing?

A

Diaphragm - responsible for 70% of muscular activity of inspiration

30
Q

What does the diaphragm separate?

A

Thoracic and abodminal cavities

31
Q

What are the muscles of inspiration?

A

Diaphragm with reasonable help from external intercostal muscles

32
Q

What are the muscles of inspiration under severe respiratory load?

A

Scalene muscles
Sternocleidomastoid muscles

33
Q

What do muscles do in expiration?

A

Passive process - external intercostal muscles stop contracting

34
Q

What do abdominal muscles act on?

A

Abdominal cavity

35
Q

What happens when abdominal muscles contract?

A

Reduce volume of abdominal cavity

Organs in abdominal cavity push up onto the diaphragm which push up on to the thoracic cavity

Decrease in thoracic cavity volume

This brings about expiration

36
Q

What happens when the diaphragm contracts?

A

Flattens down and increases volume of thoracic cavity

37
Q

What happens when the diaphragm relaxes?

A

Pushes up and volume of thoracic cavity pushes down

38
Q

What changes allow breathing to take place?

A

Changes in the thoracic cavity volume

39
Q

What is Boyle’s law fundamental in?

A

Describing why the air moved out the way it does when we breathe in and we breathe out.

40
Q

Based on Boyle’s law, what does an Increase volume in thoracic cavity result in?

A

Decreased pressure inside thoracic cavity

41
Q

Based on Boyle’s law, what does a decrease volume in thoracic cavity result in?

A

Increased pressure inside thoracic cavity

42
Q

What direction do gases move in?

A

Area of high pressure to low pressure

43
Q

What are the important gas laws?

A

Boyle’s Law
Dalton’s Law
Charles’ Law
Henry’s Law

44
Q

What does Dalton’s law state?

A

The total pressure of a gas mixture is the sum of the pressures of the individual gases

45
Q

What does Charles’s law state?

A

The volume occupied by a gas is directly related to the absolute temperature

46
Q

What does Henry’s law state?

A

The amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid

47
Q

What produces surfactant?

A

Type II Alveolar cells

48
Q

What is the purpose of surfactant?

A

Reduces surface tension on alveolar surface membranethus reducing tendency for alveoli to collapse.

49
Q

What are some of the effects of surfactant?

A
  • Reduces surface tension on alveolar surface membrane thus reducing tendency for alveoli to collapse
  • Increase lung compliance (distensibility)
  • Reduces lung’s tendency to recoil
  • Makes work of breathing easier
50
Q

When is surfactant produced?

A

Surfactant production starts ~25 weeks gestation and is complete by ~36 weeks.

Stimulated by thyroid hormones and cortisol which increase towards the end of pregnancy.

51
Q

What are premature babies at risk of developing?

A

Newborn respiratory distress syndrome (NRDS)

52
Q

What does the law of laplace state?

A

Law states that the pressure required to keep alveoli open is equal to 2 times the surface tension divided by the radius

53
Q

What obeys the law of laplace?

A

Surfactant and surface tension

54
Q

What is the equation for the law of laplace?

A

P = 2T/r

55
Q

In what kind of alveoli is surfactant more effective in and why?

A

In small alveoli than large alveoli because surfactant molecules come closer together and are therefore more concentrated.

56
Q

What is intra-thoracic (alveolar) pressure?

A

The pressure inside the thoracic cavity, (essentially pressure inside the lungs).

May be negative or positive compared to atmospheric pressure.

57
Q

What is Intra-pleural Pressure (PiP)?

A

The pressure inside the pleural cavity, is typically negative compared to atmospheric pressure (in healthy lungs at least!)

58
Q

What is transpulmonary pressure (PT)

A

The difference between alveolar pressure and intra-pleural pressure. Almost always positive because Pip is negative (in health).

PT = Palv – Pip.

59
Q

Explain why intrapleural pressure is always less than alveolar pressure.

A

During inspiration, the contractions of the diaphragm and inspiratory (external) intercostal muscles increase the volume of the thoracic cage.

Intrapleural pressure becomes more subatmospheric (negative) and causes the lungs to expand.

This expansion makes alveolar pressure subatmospheric, which creates the pressure difference between atmosphere and alveoli to drive air flow into the lungs.

During expiration, the inspiratory muscles cease contracting, allowing the elastic recoil of the chest wall and lungs to return them to their original between-breath size.

This compresses the alveolar air, raising alveolar pressure above atmospheric pressure and driving air out of the lungs.

Medicine 1 - Physiology (14 decks)

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