Flashcards in Physiology Deck (89)
What does internal respiration refer to?
The intracellular mechanisms which consume O2 and produce CO2
What does external respiration refer to?
Events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body
What are the 4 steps of external respiration?
Gas exchange (alveoli-blood)
Gas exchange (blood-tissues)
Which 3 body systems are involved in external respiration?
The mechanical process by which air is moved between the atmosphere and the alveolar air sacs
Air flows from a region of ___ pressure to ___ pressure
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)
Before inspiration, intra-alveolar pressure = atmospheric pressure. True/False?
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?
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 smaller tendency to collapse. True/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?
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