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resp physio 1 Flashcards

1
Q

define inhalation

A

the process of air flowing into the lungs during inspiration

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2
Q

define exhalation

A

the process of air flowing out of the lungs during expiration

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3
Q

how does air flow into and out of the lungs?

A

pressure differences

high pressure to low pressure

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4
Q

what causes the pressure changes in the lungs?

A

Muscular breathing movements and recoil of elastic tissues

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5
Q

what is Patm?

A

atmospheric pressure

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6
Q

at what part of the respiratory tract does pressure = Patm?

A

the beginning of the respiratory tract

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7
Q

what is PA?

A

alveolar pressure

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8
Q

what happens if Patm = PA?

A

no airflow

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9
Q

what happens if PA < Patm?

A

air flows into the lungs

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10
Q

what happens if PA>Patm?

A

air flows out of the lungs

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11
Q

what is Boyle’s Law?

A

if the volume of a gas is made to increase, the pressure exerted by the gas decreases

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12
Q

the lungs are elastic. how can they return to their original shape?

A

if the force distorting them is removed

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13
Q

how are the lungs inflated?

A

reducing the pressure outside the lungs in the thorax by lowering the diaphragm

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14
Q

under normal conditions, which way do the chest wall and the lungs pull?

A

Chest wall pulls outwards and the lungs pull inwards

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15
Q

what is the value of intrapleural pressure with respect to the atmosphere?

A

negative

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16
Q

what is the intrapleural pressure?

A

pressure/tension felt between the lungs and the chest wall

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17
Q

how does intrapleural pressure change during inspiration and expiration?

A

slightly negative at the beginning of inspiration

intra pleural pressure becomes more negative during inspiration
becomes less negative during quiet expiration

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18
Q

what happens to the intrapleural pressure in a pneumothorax?

A

equal or exceeds the atmospheric pressure

pressure surrounding lungs will increase and may cause the lungs to collapse

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19
Q

what is elasticity?

A

a measure of how easily the lungs can be stretched

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20
Q

how is elasticity expressed?

A

compliance

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21
Q

what is compliance?

A

the ease at which the lungs expand under pressure

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22
Q

what causes lung compliance to change?

A

disease

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23
Q

how is compliance calculated?

A

change in volume/change in pressure

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24
Q

at any given pressure, is lung volume lowest during inhalation or exhalation?

A

inhalation

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25
Q

even without any expanding pressure, why does the lung always have some air in it?

A

due to airway closure

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26
Q

what is airway closure?

A

where small airways close, trapping gas in alveoli

27
Q

when does airway closure increase?

A

in certain conditions such as age and lung disease

28
Q

what causes reduced compliance?

A

Increase of fibrous tissue in the lung (pulmonary fibrosis)
Collapse/closure of lung (Atelactasis)
Increase in pulmonary venous pressure

29
Q

what causes increased compliance?

A

age

emphysema

30
Q

how does emphysema affect the lung?

A

destruction of normal lung architecture - includes elastic fibres and collagen
impaired elastic recoil
lungs don’t deflate as easily
lung is more easily distended - increased compliance

31
Q

how does fibrosis affect lung compliance?

A

decreases compliance

32
Q

what is kyphoscoliosis?

A

a disorder characterized by progressive deformity of spine

33
Q

what components generate the elastic quality of the lungs?

A

elastic fibres and collagen

surface tension forces caused by the alveolar-liquid interface

34
Q

what forms the majority of connective tissue in the alveoli walls?

A

elastic fibres

35
Q

is more pressure needed to inflate an air filled lung or deflate it?

A

inflate it

36
Q

what is hysteresis?

A

means to lag behind

A greater pressure is required to reach a specific lung volume when you are inflating it rather than deflating it.

37
Q

is more pressure needed to inflate a fluid filled lung or deflate it?

A

deflate it - the air-fluid interface has been abolished

38
Q

what is surface tension?

A

cohesive forces between liquid molecules at the surface

molecules at the surface have stronger bonds to those underneath them

39
Q

explain surface tension elastic force

A

on the inner surface of the alveoli, the water surface is always trying to contract
alveoli try to collapse
an elastic force has to be generated throughout the lung

40
Q

explain Laplace’s Law and given an equation

A

P = 2T/r

The pressure in a bubble is equal to twice the surface tension divided by the radius

The smaller the bubble, the greater the internal pressure required to keep it inflated

41
Q

how do the lungs compensate with problem of pressure differences arising from having alveoli of different sizes?

A

surfactants stabilise alveoli
without surfactant, pressure would be greater in smaller alveoli.
surfactant lowers surface tension more in smaller alveoli

42
Q

what effect do surfactants have on surface tension?

A

reduce surface tension

reduce surface tension elastic forces

43
Q

what is pulmonary surfactant made of?

A

a complex mixture of lipids and proteins

44
Q

how do surfactants reduce surface tension?

A

Amphipathic character (hydrophilic/water loving head groups and hydrophobic tails towards air) and resultant packing reduces surface tension

45
Q

what cells secrete surfactant?

A

type 2 alveolar epithelial cells

46
Q

where does assembly of surfactants occur?

A

in the lamellar bodies

47
Q

what is surfactant secreted into and what occurs to it at this point?

A

into alveolar fluid
undergoes structural changes to form a meshwork known as tubular myelin before eventually forming a surfactant layer at air-water interface

48
Q

what causes infant respiratory distress syndrome?

A

developmental insufficiency ofsurfactantproduction and structural immaturity in thelungs

49
Q

what is airway resistance?

A

the resistance to the flow of gas within the airways of the lung

50
Q

what is an example of a disease that might affect airway resistance?

A

asthma

51
Q

what causes asthma?

A

Reduction of airway diameter due to contraction of smooth muscle or swelling due to inflammation and mucus production

52
Q

what controls the tone of the smooth muscle in the airways?

A

autonomic nervous system

53
Q

what affects the pattern of fluid flow through a tube?

A

velocity and physical properties

54
Q

what are the types of airway flow in the lungs?

A

laminar - movement is orderly and streamlined

turbulent - chaotic

55
Q

which law describes laminar flow?

A

Poiseuille’s Law

56
Q

what does Poiseuille’s Law state?

A

Small changes in the diameter of airways leads to relatively big changes in flow.

57
Q

what are sites of airway resistance in the upper respiratory tract?

A

the nose

58
Q

Assuming laminar flow, Poiseuille’s law would predict that major resistance to air flow would occur in airways with smaller radius.
Why is this not so?

A

Because the total cross-sectional area increases as you go down the tracheobronchial tree - although the diameter of each airway is small there are a larger number of them

59
Q

what controls the resistance of small bronchi and bronchioles?

A

neuronal and hormonal factors

60
Q

how does the parasympathetic system control bronchial smooth muscle tone?

A

postganglionic fibres release Ach which stimulate muscarinic receptors on smooth muscle causing them to contract.

61
Q

how does the sympathetic system control bronchial smooth muscle tone?

A

occurs mainly via circulating catecholamines. Adrenalin activates β2 receptors causing smooth muscle to relax

62
Q

what are other factors which contribute to bronchomotor tone?

A
  • Non-adrenergic non cholinergic systems, NANC
  • Mediator release (e.g histamine etc)
  • Rapidly adapting pulmonary receptors (irritant/cough receptors)
  • Slowly adapting/stretch pulmonary receptors
  • carbon dioxide - causes bronchodilation in underventilated areas where the gas builds up
63
Q

what does the work of breathing have to overcome?

A

resistance to airflow

elastic recoil of the lungs

c (25 decks)

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