Respiratory Physiology- relating structure to function Flashcards
What is meant by TV?
Tidal volume.
Define tidal volume.
The volume of air breathed in and out of the lungs at each breath.
What is meant by ERV?
Expiratory Reserve Volume
Define Expiratory Reserve Volume
The maximum amount of air expelled from the lungs at the end of normal respiration.
What is IRV?
Inspiration Reserve Volume
Define Inspiration Reserve Volume
The maximum amount of air which can be drawn into the lungs at the end of regular respiration.
What is RV?
Residual volume.
Define Residual volume.
The volume of gas left in the lungs at the end of maximal expiration.
What is VC?
Vital capacity.
How is vital capacity calculated?
tidal volume + inspiratory reserve volume + expiratory reserve volume.
What is TLC?
Total lung capacity
How is total lung capacity calculated?
vital capacity + the residual volume
What is IC?
Inspiratory capacity
How is inspiration capacity calculated?
tidal volume + inspiratory reserve volume
What is FRC?
Functional residual capacity
How is functional residual capacity calculated?
expiratory reserve volume + residual volume
What is FEV1:FVC?
Fraction of forced vital capacity expired in 1 second
What is the dead space volume value?
150ml
What is the value for tidal volume?
500ml
How many lobes does the external right lung have?
3
How many lobes does the external left lung have?
2
How many membranes are each lung enclosed in?
2
Name the two membranes covering the lungs.
Visceral and parietal.
What does the visceral pleural membrane line?
The outer surfaces of the lungs.
What does the parietal pleural membrane line?
Inner surface of the ribs
What is located between the two pleura membranes?
Pleural fluid
What are the functions of the pleura membranes?
The ‘stick’ the lungs to the membrane
What is the visceral pleura ‘stuck’ to?
-Surface of the lungs
-Parietal pleura via the cohesive forces of the pleural fluid
What is the parietal pleura ‘stuck’ to?
Rib cage and diaphragm
What leads the expansion of the lung during inspiration?
The chest wall
What leads to the recoil of the chest wall in (unforced) expiration?
Elastic connective tissue in the lung
What does Boyle’s Law state?
States that pressure exerted by a gas is inversely proportional to it’s volume.
Why does bretahing occur?
Because the volume of the thoracic cavity changes volume.
Based on Boyle’s law, what happens when there is an increase in volume?
Decrease in pressure
Based on Boyle’s law, what happens when there is an decrease in volume?
Increase in pressure.
What direcetion do gases always move?
High to low pressure.
Expiration is passive at rest but what does it use during severe respiratory load?
Internal intercostal and abdominal muscles
List the muscles used for inspiration.
Diaphragm, external intercostals, sternocleidomastoids and scalenes.
List the muscles used for expiration.
Passive Process.
But, can sometimes use internal intercostals and abdominals.
At rest, what happens to the diaphragm?
It’s relaxed
What happens to the diaphragm during inspiration?
It contracts and thoracic volume increases.
What does the ‘pump handle’ motion do?
Increases anterior-posterior dimension of the rib cage.
What does the ‘bucket handle’ motion do?
Increases lateral dimension of the rib cage
What happens to the diaphragm during expiration?
Diaphragm relaxes and thoracic volume increases.
What is Intra-thoracic (Alveolar) Pressure?
Pressure inside the thoracic cavity,
Is Intra-thoracic (Alveolar) Pressure usually positive or negative?
May be negative or positive compared to atmospheric pressure.
What is Intra-pleural Pressure ?
Pressure inside the pleural cavity.
How does the value of Intra-pleural Pressure compare to the vlaue of Intra-thoracic pressure?
Usually negative.
What is Transpulmonary pressure ?
Difference between alveolar pressure and intra-pleural pressure.
Is transpulmonary pressure usually positive or negative?
Nearly always positive/
How many cell types are alveolar walls made up of?
2 (type I and type II)
Describe type I cells.
Thin walled which permit gas exchange.
Describe Type II cells.
Specialised cells which secrete surfacacnt fluid.
What is the function of surfacant?
Reduces surface tension on alveolar surface membrane reducing risk of the alveoli collapsing.
What is surface tension?
Attraction between water molecules
Where does surface tension occur?
Wherever there is an air-water interface
What does surfacact do to lung compliance?
Increases lung compliance.
What does surfactant do to breathing?
Makes breathing easier.
What does surfactant do in terms of recoiling?
Reduces the lungs abaility to recoil.
In which types of alveoli is surfactant most effective?
In small alveoli as the surfactant molecules come closer together and are more concentrated.
Is pressure greater in large or small alveoli?
Small
When does the production of surfactant start in the body?
At 25 weeks of gestation
When is the production of surfactant complete?
36 weeks
What are premature babies more at risk at as the surfactant production hasn’t completed?
Infant Respiratory Distress Syndrome
Describe the law of LaPlace in terms of keeping alveoli open.
The law states that in order for the alveoli to remain open, the pressure must be equal to two times the surface tension divided by the radius.
Define compliance.
Change in volume relative to changes in pressure.
What does compliancy represent?
The stretchability of the lungs.
->how easy it is to get air into the lungs.
What does a high compliance mean?
Large increase in lung volume for small decrease in ip pressure
What does a low compliance mean?
Small increase in lung volume for large decrease in ip pressure
