lungs, pleura and ventilation Flashcards
ventilation: explain the movements involved in normal, vigorous and forced ventilation and describe the muscles responsible for these movements
ventilation perfusion matching: ventilation
gravity pulls alveoli down inferiorly; higher pressure and stretched at top; greater pressure to inflate superior more as already stretched so less scope for increasing size; PPL more negative and greater transmural pressure gradient, alveoli larger and less complient so less ventilation superiorly
ventilation perfusion matching: perfusion
similar - path of least resistance; greater impact of perfusion than ventilation; as blood flow denser more susceptible to effect of gravity; higher intravascular pressure at base (gravity) as more recruitment, less resistance, higher glow rate
ventilation:perfusion ratio
e^x graph - tends towards 0 then curves up to infinity
define transit time
amount of time blood in contact with respiratory exchange surfaces - short as otherwise will equilbriate; during exercise, if cardiac output increases, blood goes through faster
functions of conduit airways
conduct O2 to alveoli, conduct CO2 out of lung (gas exchange)
how is it facilitated
mechanical stability (cartilage), control of calibre (smooth muscle), protection and ‘cleansing’
what controls and what produces breathing
nervous system, skeletal muscle
what are the gas exchange areas called
alveolar sacs
how can the capacity of the thoracic cavity be increased
movements of diaphragm, movements of ribs
how does skeletal muscle result in mechanism of breathing
pleural cavity expanded by muscles in walls → elastic lungs expand with pleural cavity, sucking air down trachea and bronchi into lungs
what is the main inspiratory muscle
diaphragm
diaphragm mechanism of breathing
contraction causes it to press on abdominal viscera which initially descend → further descent stopped by abdominal viscera, so more diaphragm contraction raises costal margin → increased thoracic capacity produced by diaphragm and rib movements in inspiration, reduces intraplueral pressure, with entry of air and expansion of lungs
during breathing, why are the ribs elevated
increases antero-posterior dimension of thoracic cavity (pump-handle)
during breathing, why are the ribs everted
increases transverse diameter of thoracic cavity (bucket-handle)
why do internal and external intercostal muscles stiffen rib cage
increase efficiency of diaphragm
