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21- Head and Thorax > Ventilation and perfusion > Flashcards

Ventilation and perfusion Flashcards

1
Q

Describe the conducting zone of the respiratory system

A

trachea to the bronchioles

where there is no gas exchange

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2
Q

Describe the respiratory zone of the respiratory system

A

respiratory bronchioles to the alveoli

where there is gas exchange

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3
Q

How does inspiration occur

A
  • Diaphragm contracts and flattens and moves caudally
  • Ribs are pulled cranially and outwards by contraction of the external intercostal muscles
  • Together these increase the volume of the thoracic cavity, decreasing the pressure of the air in the alveoli and causing air to be sucked in as air flows from high to low pressure
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4
Q

How does expiration occur

A
  • Is a passive response except during exercise
  • The diaphragm relaxes and raises
  • intercostal muscles relax and ribs and sternum go down
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5
Q

Describe the composition of the diaphragm

A

central part= tendinous

Peripheral = muscular

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6
Q

What is the diaphragm attached to

A
  • xiphoid process
  • lower costal cartilages
  • ribs
  • vertebral column
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7
Q

Describe the crura of the diaphragm

A

right and left crus or fibromuscular bands arising from the ;lumbar vertebrae, insert into the central tendon of the diaphragm

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8
Q

Name the 3 things that pass through the diaphragm

A
  • oesophagus
  • aorta
  • vena cava
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9
Q

What nerve innervates the diaphragm

A

phrenic nerve

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10
Q

Where do external intercostal muscles lie

A

superficially and the fibres run caudoventrally between ribs

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11
Q

where do internal intercostal muscles lie

A

lie underneath and fibres run in the opposite direction

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12
Q

Name the 2 components of internal intercostal muscles

A

interosseous

interchondral

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13
Q

Describe the interosseous part of the internal intercostal muscles

A

expiratory muscles between bones

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14
Q

describe the interchondral part of the internal intercostal muscles

A

inspiratory muscles between cartilage

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15
Q

Describe the parietal pleura

A

outer layer of pleura lying closer to the ribs and chest wall

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16
Q

Describe the visceral pleura

A

inner layer of pleura lying closer to the lung tissue

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17
Q

Describe the pleural cavity

A

the space between the folds of the pleura

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18
Q

how does locomotion affect ventilation

A

stride cycle and ventilation cycle of galloping animals are synchronized, piston pendulum theory, movement of the limbs influences inspiration and expiration, inspiration only when the body is extended due to negative pressure in the thorax

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19
Q

What are the factors influencing ventilation

A
  • resistance to flow in the airways
  • lung compliance
  • alveolar surface tension
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20
Q

What is the calibre or airways

A

internal diameter

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21
Q

What are the smooth muscles of the airway walls

A

bronchial muscle- musculus spiralis

22
Q

describe the laminar flow

A

a smooth pattern of flow

23
Q

describe turbulent flow

A

irregular flow with random variations in pressure

24
Q

Where is turbulence greatest

A

in trachea and bronchi

25
Q

what is compliance

A

change in volume of a structure for eac unit change in pressure

26
Q

what is elastance

A

retractive (recoil) force that the distension of a structure generates

27
Q

How is surface tension in the alveoli reduced

A

surfactant

28
Q

how is the pressure inside the alveolus determined

A

by the surface tension of the lining fluid and the radius of the alveolus

29
Q

Why is surfactant more concentrated in smaller alveoli

A

the surface tension is higher in smaller alveoli

30
Q

Define tidal volume

A

Is the amount of air breathed in or out during a respiratory cycle. It can increase or decrease from normal depending on ventilation requirements

31
Q

Define inspiratory reserve volume

A

is the amount of air that can still be inspired after inhaling the tidal volume

32
Q

Define expiratory reserve volume

A

is the amount of air that can still be expired after exhaling the tidal volume

33
Q

Define residual volume

A

is the amount of air remaining in the lungs after the most forceful expiration

34
Q

Define inspiratory capacity

A

is the sum of the tidal and inspiratory reserve volumes

35
Q

Define vital capacity

A

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

36
Q

Define functional residual capacity

A

Is the sum of the expiratory reserve volume and the residual volume

37
Q

Define total lung capacity

A

Is the entire gas volume of the maximally spontaneously inflated pulmonary parenchyma and airways in the thorax

38
Q

Define respiratory rate

A

Is the rate at which breathing occurs. This is usually measured in breaths per minute

39
Q

Define minute ventilation

A

Is the total volume of gas moved in or out of the airways and alveoli in 1 minute

40
Q

Define dead space

A

Is the volume of air that is inhaled that does not take part in the gas exchange, because it either remains in the conducting airways or reaches alveoli that are not perfusion or poorly perfused

41
Q

Define alveolar ventilation

A

Is defined as the volume of air entering and leaving the alveoli per minute

42
Q

Describe the regional differences in ventilation

A

lower portions of the lung are ventilated more than upper zones

43
Q

What is pulmonary perfusion

A

blood flow to the alveoli allowing uptake of oxygen and removal of carbon dioxide

44
Q

list 4 factors affecting perfusion

A
  • hypoxic vasoconstriction
  • disease
  • posture
  • cardiac function
45
Q

Describe hypoxic vasoconstriction

A

reduces blood flow to the alveoli that aren’t being ventilated in order to send blood to ventilated areas

46
Q

What is ventilation and perfusion mismatch

A

where the ventilation and perfusion don’t match and aren’t even across the lung

47
Q

Describe the V/Q at base of lung

A

low as there is more blood flow than ventilation

48
Q

Describe the V/Q at apex of the lung

A

high as there is more ventilation than blood flow

49
Q

Describe mismatching of ventilation due to posture

A

ventilation is less in dorsal areas and can become restricted when the animal is lying down due to the lungs becoming crushed

50
Q

Explain how ventilation is regulated

A

Is regulated by the respiratory centre in the medulla, which generates action potentials, modulated by feedback from:

  • Chemorecptors
  • Mechanorecptors

21- Head and Thorax (8 decks)

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