Respiratory physiology 2 Flashcards
What is the appoximate total volume of a lung?
6L
What volume of air do the lungs normally contain at a normal respiration rate?
2.8L, however normally not all 2.8L are breathed out during expiration. typically 500ml
Define ‘tidal volume’
The volume of air breathed in and out of the lungs at each breath
Define ‘ Expiratory reserve volume’
The maximum volume of air which can be expelled from the lungs at the end of a normal respiration
Define ‘Inspiratory reserve volume’
The maximum volume of airw which can be drawn into the lungs at the end of a nromal inspiration
Define ‘Residual volume’
The volume of gas in the lungs at the end of a maximal expiration
Define ‘vital capacity’
Total lung volume minus the residual volume. Essentially the total amount of air you can expire in one exhalation after fully filling up your lungs
Define ‘functional residual capacity’
Volume of lungs at the end of a full relaxed exhalation
Define ‘ inspiratory capacity’
tidal volume + inspiratory reserve volume
How many pleural cavities are in the respiratory system
2 lungs = 2 pleural cavities
Descibe what is meant by the ‘hilum of the lungs’
Point at which the lungs connect with the major airways
Describe the parts of the pleural cavity
Visceral and parietal
Describe the parietal aspect of the pleural fluid in the cavity
Part which is closes to the ribs and inferiorly stuck to the diaphragm
Describe the visceral aspect of the pleural fluid in the cavity
Membrane attached to the organ of the lung (inner bit)
What does the fluid in the plural sac allow for?
Friction free movement of the lung as parietal and visceral membranes remain in contact and glide across each other
Define ‘ pleurisy’
Inflammation of the pleural membranes
Define ‘pneumothorax’
When air is in the thoracic cavity, normally due to penetrating wounds to the chest
How are the lungs stuck to the chest wall
Through the cohesive forces of the pleural membrane.
As the pleural fluid stops the lungs recoiling which results in a cohesive force against the elastic fibres which hold the lungs to the chest wall
Why do alveoli not completely collapse and expire all air during expiration
Alveoli stay partially inflated to decrease energy loss
State boyle’s law
The pressure exerted by a gas is inversely proportional to its volume.
e.g increased volume = decreased pressure.
decrease volume = increased pressure
Gasses always move from ____ to ____ pressure
High to low pressure
What are the muscles involved in expiration?
Internal intercostal muscles And abdominal muscles
Describe the mechanism of the internal intercostal muscles within expiration
- Run in opposite direction to external intercostal muscles
- Pull the rib cage downwards and inwards
- Results in less volume = increases pressures and gas flows out
Describe the mechanism of the abdominal muscles within expiration
- Push organs up against diaphragm which decreases volume of thoracic cavity
- Results in increased pressure in thoracic cavity which increases pressure
Describe how the scalenes and the stemocleoidomastoids are used in increased respiratory load
They are used to expand the chest to allow more air into the thoracic cavity
The diaphragm is responsible for what % of muscular activity during inspiration
70%
What are intercostal muscles?
Muscles that run in between the ribs
What type of intercostal muscle aids inspiration?
External intercostal muscles
When are the Scalenes and stemocleoidmastoids used in respiration?
- During increased inspiratory load
- Used to expand the chest to allow more air into thoracic cavity
Describe the internal intercostal muscles
- Run in opposite direction to external intercostal muscles
- Pull the ribcage downwards and inwards to air expiration
Describe the abdominal muscles role in respiration?
- Push organs up against the diaphragm which decreases volume of thoracic cavity
What are the muscles of expiration?
Internal intercostal muscles
Abdominal muscles
What nerve innervated the diaphragm?
Phrenic nerve
What happens when the diaphragm contracts?
- Increases the volume as the diaphragm becomes more straight
- Pressure inside thoracic cavity becomes less than atmospheric pressure which causes inspiration
What happens when the diaphragm relaxes?
- The volume of the thoracic cavity decreases
- pressure increases
- Expiration
Describe the role of the external intercostal muscles within respiration?
- Raise the ribcage upwards and outwards
- When they contract they lift up the sternum by lifting up the ribcage
- Creates an increase in anterior posterior dimensions of thoracic cavity between sternum and sternum
- Increases the lateral dimensions via the ribs
- This aids inspiration as the increasing dimension helps decrease pressure
Describe the role of the internal intercostal muscle within respiration
- Pull the ribcage down and decrease space
- Diameter of airways increases during inspiration and decreases during expiration
- (Opposite of external intercostal muscle)
Define ‘intra-thoracic alveolar pressure’
Pressure inside the thoracic cavity
Explain what is meant by the intra thoracic alveolar pressure being:
- Positive
- Negative
Positive = greater than atmospheric pressure. Expiration Negative = less than atmospheric pressure. Inspiration
Describe intra pleural pressure
- Usually negative
- Can become positive in some pathological situations
What is meant by ‘transpulmonary pressure’
The difference between the alveolar pressure and the intra pleural pressure
the transpulmonary pressure is always what?
Positive as the intra pleural pressure is always negative
Describe surfactant
- Detergent like fluid produced by type II alveolar cells
What is the effect of surfactant?
Reduces surface tension on alveolar membrane thus reducing the tendency for alveoli to collapse
What is meant by surface tension and when does it occur?
Whenever there is an air-water interface and refers to the attraction between the water molecules
What is the effect of air needing to be fully saturated before it can diffuse from alveoli to the blood?
- Produces layer of fluid on surface level of alveoli and ir in the middle - air water interface
THIS PRODUCES SURFACE TENSION BBBYYYYYYY
Explain the mechanism of how surfactant prevents the collapse of alveoli
- Surface layer of water would create an inwardly directed pressure that would collapse alveoli as water is attracted to itself
- Surfactant reduces attraction between water molecules
- This reduces surface tension between water molecules. means alveoli don’t collapse
Does surfactant increase or decrease lung complaince?
Increases
Does surfactant increase or decrease lung’s tendancy to recoil?
Reduces
Is surfactant more effective is small or large alveoli?
More effective in small alveoli than large alveoli because surfactant molecules come closer together and are therefore more concentrated
At what stage of gestation does surfactant production start and end?
- starts ~25weeks gestation
- Complete ~36 weeks gestation
What stimulates surfactant production?
Thyroid hormones and cortisol which increases towards the end of the pregnancy
Describe infant respiratory distress syndrome
When premature babies do not have sufficient surfactant levels when born
Define ‘complaince’
Change in volume relative to change in pressure.
- i.e how much does volume change for any given pressure.
- This represents the stretchability of the lungs not the elasticity
