Respiratory system 4 Flashcards
How do you form a pressure gradient
Your diaphragm drops while rib cage expands - increases volume and lowering pressure
Pressure gradient during inhalation
Vol. increasing - pressure in lungs decreases
Pressure out now greater then inside so air rushes in
Pressure gradient during exhalation
Vol. decreasing - pressure in lungs increasing.
Pressure outside lower than inside so air rushes out
What are the two opposing forces overcome to take a breath
Stiffness - how easy lungs can expand - surface tension holds lungs in place
Resistance - How easy to move air in and out
What is compliance
Magnitude of change in volume produced by given change in pressure
V/P= C
What does low compliance means for lungs
‘stiff lungs’ - more work to expand.
Thickening and scaring of alveolar membranes - caused by chronic inflammation or exposure to industrial chemicals
How does Surface tension affect breathing
Alveoli lined with fluid that exerts surface tension - very thin
Must overcome surface tension to expand lungs
What is surfactant
Lowers surface tension - reducing attractive forces between fluid molecules - increases compliance
Where is surfactant produced
Alveolar type 2 pneumocytes - main constituent phospholipids
What is the formula for resistance
R = 1/r^4
What is the main area of resistance
Bronchi
small airways contribute very little - high cross sectional area
How can we measure volume inspired/exhaled
Spirometry - pulmonary function test - measures how much and how fast
What is tidal volume (VT)
Vol. of air moved in and out during normal quiet breath
What is inspiratory reserve volume (IRV)
extra volume that can be inhaled over and above tidal vol.
What is Expiratory reserve volume (ERV)
Extra vol. that can be exhaled voluntarily after completion of normal, quiet respiratory cycle
