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Respiratory > physiology > Flashcards

physiology Flashcards

1
Q

What are the 4 steps of external respiration

A
  1. Ventilation
  2. Gas exchange- alveoli & blood
  3. Gas transport in blood
  4. Gas exchange at tissue level
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2
Q

What 3 forces keep alveoli open

A
  1. Transmural pressure gradient
  2. Pulmonary surfactant
  3. Alveolar interdependence
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3
Q

What is pulmonary surfactant

A

Reduces surface tension

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4
Q

What 2 elastic forces promote alveolar collapse

A
  1. Elastic recoil of lungs & chest wall
  2. Alveolar surface tension
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5
Q

What 2 factors make lungs adhere to chest wall

A
  1. Transmural pressure gradient
  2. Intrapleural fluid cohesiveness
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6
Q

how is transmural pressure gradient made across lung & chest wall

A

sub-atomic atmospheric pressure

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7
Q

How is the intrapleural fluid cohesive (what does this do to pleural membranes)

A

Water molecules in the fluid resist being pulled apart so
-pleural membranes stick together

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8
Q

What 3 pressures are important in ventilation

A

Atmospheric (760mmHg at sea level)
Intra-alveolar (760mmHg)
Intrapleural (756mmHg)

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9
Q

What pressures push outwards & inwards on the lung wall

A

Intra-alveolar pushes outwards
Intrapleural pushes inwards

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10
Q

What does the 4mmHg difference in intra-alveolar & intrapleural result in

A

Constitutes transmural pressure gradient pushing OUT on the lungs
-Stretches them to fill thoracic cavity

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11
Q

What pressure gradient is essential for expansion of the lungs

A

Transmural
-Relationship between differences in intra-alveolar & intrapleural pressures

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12
Q

What condition abolishes transmural pressure gradient

A

Pneumothorax
-By raising intrathoracic pressure when air enters pleural space

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13
Q

What is boyle’s law

A

Pressure exerted by a gas varies INVERSELY with volume of the gas

e.g. As volume of gas increases pressure exerted by the gas decreases

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14
Q

which alveoli have higher tendency to collapse: small or big alveoli?

A

Small more likely to collapse

-Surfactant prevents this (reduces surface tension more in smaller ones)

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15
Q

What happens if an alveolus starts to collapse

A

surrounding alveoli stretch & recoil exerting expanding forces onto collapsing alveolus to OPEN IT
-Alveolar interdependence

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16
Q

What causes respiratory distress in premature newborns

A

Not having enough pulmonary surfactant as not synthesised until late in pregnancy

17
Q

What are the major inspiratory muscles

A

Diaphragm & external intercostal muscles

18
Q

What are the accessory inspiratory muscles

A

Sternocleidomastoid
Scalenus
Pectoral

19
Q

What are the active muscles of respiration

A

Abdominal muscles
Internal intercostal muscles

20
Q

What is tidal volume - TV

A

volume of air entering or leaving the lungs in a single breath
Average = 0.5 L

21
Q

What is inspiratory reserve volume - IRV

A

Extra volume of air that can be maximally inspired above resting TV
Average = 3L

22
Q

What is expiratory reserve volume (ERV)

A

Extra volume of air that can be actively expired by maximal contraction after resting TV
Average = 1L

23
Q

What is residual volume (RV)

A

Minimum volume of air remaining in lungs after maximal expiration
Average = 1.2L

24
Q

What is inspiratory capacity (IC)

A

Maximum volume of air inspired at end of normal quiet expiration
IC = IRV + TV
Average = 3.5 L

25
Q

What is functional residual capacity (FRC)

A

Volume of air in lungs at end of normal passive expiration
FRC = ERV + RV
Average = 2.2L

26
Q

What is vital capacity -VC

A

Maximum volume of air moved out during a single breath after maximum inspiration
VC = IRV + TV + ERV
Average = 4.5L

27
Q

What is total lung capacity - TLC

A

Total volume of air lungs can hold
TLC = VC + RV

28
Q

What volume increases when elastic recoil of lung is lost e.g. in emphysema

A

Residual volume

29
Q

What is forced vital capacity FVC

A

maximum volume that can be forcibly expelled from the lungs following a maximum inspiration

30
Q

What is forced expiratory volume in 1 second FEV1

A

volume of air that can be expired during the first second of expiration in an FVC

31
Q

What is the FEV1/FVC ratio

A

proportion of the Forced Vital Capacity that can be expired in the first second
= (FEV1/FVC) X 100% - Normally more than 75%

32
Q

What do parasympathetic + sympathetic stimulation do to airways

A

Parasympathetic = bronchoconstriction

Sympathetic = Bronchodilation

33
Q

What factors decrease pulmonary compliance

A

Pulmonary fibrosis
Pulmonary oedema
Lung collapse
Pneumonia
Absent surfactant

34
Q

What is pulmonary compliance

A

Measures the effort that goes into stretching & distending the lungs

35
Q

what does decreased pulmonary compliance cause

A

SOB especially on exertion
greater pressure change required to give change in volume
(basically STIFF LUNGS)

36
Q

What happens if pulmonary compliance increases

A

Emphysema
Elastic recoil of lungs is lost so having to work harder to get air OUT OF lungs

37
Q

What causes increased work of breathing

A

Decreased pulmonary compliance
Airway resistance increases
Elastic recoil decreases
Increased ventilation (gas moving in and out of lungs)

38
Q

What is anatomical dead space

A

where some air remains in airways, not available for gas exchange

Respiratory (6 decks)

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