Physiology Flashcards
Air flows from a region of ___ pressure to ___ pressure
High, low
Intra-alveolar pressure must be greater than atmospheric pressure for air to flow into the lungs. True/False?
Intra-alveolar pressure must be less than atmospheric pressure, since air flows from high to low pressure
At constant temp, as the volume of a gas increases, the pressure exerted _____ (Boyle’s Law)
Decreases
Before inspiration, intra-alveolar pressure = atmospheric pressure. True/False?
True
Which 2 forces hold the lung and thoracic wall in close opposition?
Intrapleural fluid cohesiveness
Negative intrapleural pressure
Describe intrapleural fluid cohesiveness
Water molecules present in intrapleural fluid are attracted to each other/resist being pulled apart
This causes pleural membranes to stick together
Describe the effect of sub-atmospheric intrapleural pressure
Creates a transmural pressure gradient across the lung and chest wall, causing lungs to expand outwards while the chest squeezes inwards (inspiration)
Intra-alveolar pressure = 760
Intrapleural pressure = 756
What happens across the lung wall?
Lungs expand outwards
Intrapleural pressure = 756
Atmospheric pressure = 760
What happens across the thoracic wall?
Chest squeezes inwards
Contraction of the diaphragm causes the volume of thorax to increase in which direction?
Vertically
What is the function of external intercostal muscle in inspiration?
Lifts ribs up, pushes out sternum
What is a pneumothorax?
Air in the pleural space
What is the function of surfactant?
Reduces alveolar surface tension
Smaller alveoli have a greater tendency to collapse. True/False?
False
More likely to collapse
What secretes surfactant?
Type II alveoli
What cause respiratory distress syndrome in new borns?
Not enough surfactant, leading to high alveolar surface tension
Describe alveolar interdependence
When one alveoli starts to collapse, surrounding alveoli recoil in resistance, pulling the collapsing alveoli open
What are the 2 main accessory muscles of respiration?
Scalenus
Sternocleidomastoid
What is meant by tidal volume?
Volume of air entering/leaving the lungs in a single breath
What is meant by inspiratory reserve volume?
Volume of air that can be maximally inspired beyond the tidal volume
What is meant by inspiratory capacity?
TV + IRV
What is meant by expiratory reserve volume?
Volume of air that can be maximally expired beyond the tidal volume
What is meant by residual volume?
Volume of air remaining in lungs after maximal expiration
What is meant by functional residual capacity?
Volume of air remaining in lungs following normal expiration
ERV + RV
What is meant by vital capacity?
Volume of air that can be maximally expired following maximal inspiration
TV + IRV + ERV
What is meant by total lung capacity?
Maximum volume of air the lungs can hold
VC + RV
Residual volume can be measured with a spirometer. True/False?
False
What is meant by forced vital capacity?
Volume of air that can be forcefully maximally expired following maximum inspiration
In obstructive airways disease, FVC is low and FEV1 is low, but the FEV1/FVC ratio stays the same. True/False?
False
FVC is normal/low, FEV1 is low, FEV1/FVC ratio is reduced
In restrictive airways disease, FVC is ___ and FEV1 is ___, and the FEV1/FVC ratio is ____
Low, low, normal