L2-ventilation and lung mechanics Flashcards
what do the muscles of respiration include?
the diaphragm, muscles of inspiration and expiration
what is the structure of the diaphragm
a large dome shaped muscle upon which the lungs rest
where does the diaphragm arise from
lateral and posterior walls of the body cavity
what happens to the muscles of respiration during inspiration
contractions of the diaphragm are combined with contractions of muscles associated with an elevation of the ribs
what happens to the muscles of respiration during expiration
the muscles associated with inspiration relax and the elastic properties of the lungs promotes a return to the resting volume
what is required for air to flow in and out of the lungs
there has to be an associated pressure difference between the internal environment of the lungs and the external environment
what can the movement of the air in the lungs be compared to
the flow of fluids in tubes
how can you calculate the flow rate
F= (P1-P2)/R
P1=the pressure at point P1
P2= the pressure at point P2
R=the resistance to flow
what can be used to describe the pressure in the alveoli
boyles law
what does boyles law state
pressure of a gas is inversely proportional to the volume
what equation is used to describe the relationship of boyles law
P=nRT/V P=pressure n=number of moles of gas R=gas constant T=absolute temperature (degrees kelvin) V=volume
what are the 2 possible reasons for collapse of the lungs
elastic recoil
surface tension
what is elastic recoil?
based upon the elastic properties of the alveolar walls
what is surface tension?
formation of the droplets in the alveoli can cause the alveolar membranes to be drawn together resulting in alveolar collapse
how is collapse of the lungs prevented
combination of surfactant and intrapleural pressure
what is surfactent
a mixture of lipoproteins
where is surfactant secreted from
surfactant is secreted by the alveolar epithelium
what is the attractive force produced by surface tension with surfactant present
4mm Hg
what is the attractive force produced by surface tension without surfactant
between 20-30 mm Hg
what else does intrapleural pressure help
prevention of alveolar collapse
what happens to intrapleural pressure during expiration
will drop to about 2 mm Hg below atmospheric pressure (atmospheric pressure=760mm Hg)
when does elastic recoil stop
elastic recoil stops as it comes to balance with the negative intrapleural pressure
what is the compliance of the lungs and thorax
the ability to expand
how is the compliance of the lungs and thorax measured
measured in terms of the increased lung volume per unit of pressure change in intrapulmonary pressure
