lecture 17 Flashcards
how does the body create a pressure gradient?
as you inhale your diaphragm drops while your ribcage expands, decreasing volume and lowering the pressure
What is the main factor for pressure gradient during inhalation?
the pressure outside is now greater than inside, so air rushes in
What are the two opposing forces that must be overcome to take a breath?
Stiffness of the lungs
resistance of the airways to the lungs
what is compliance?
the magnitude of the change in lung volume produced by the given change in pressure
What is vital capacity?
lung volume
What is a cause of stiff lungs?
Pulmonary fibrosis
What causes pulmonary fibrosis?
Thickening and scarring of the alveolar membranes can arise from chronic inflammation or exposure to industrial chemicals
What must you overcome to expand the lungs?
the surface tension form thin alveoli walls lined with fluid
What is surfactant?
Major constituent is phospholipids which reduces surface tension in alveoli
What produces surfactant?
Type II pneumocystis
How does surfactant lower surface tension?
Reduces attractive forces between fluid molecules lining alveoli making it easier to increase lung size
Lack of surfactant causes?
Stiff lungs
What is respiratory distress syndrome (RDS)?
when premature infants do not produce surfactant
What force must the air moving to alveoli overcome?
Friction
Where does most of the resistance to airflow arise?
in the bronchi
Why do small airways contribute very little to resistance?
high cross-sectional area
how do you measure how big of a breath you can take?
Spirometer
What does a spirometer measure?
Volume inspired / exhaled
What is tidal volume?
volume of air moved in and out during normal quiet breath
What is inspiratory reserve volume?
Extra volume that can be inhaled over and above the tidal volume
What is expiratory reserve volume?
extra volume that can be exhaled voluntarily after completion of a normal quiet respiratory cycle
What is residual volume?
volume in lungs after maximal exhalation
what is minimal volume?
volume remaining in lungs if lungs collapsed
Vital capacity?
IRV + ERV + TV
Total lung capacity?
Vital capacity + residual volume
inspiratory capacity?
inspiratory reserve + tidal volume
total volume of air that can be inspired from rest
Functional residual capacity?
expiratory reserve + residual volume
Volume remaining in lungs after normal exhalation
What is a normal FEV1/FVC ratio?
80%
What do diseases like asthma reduce?
forced expiratory volume in one second FEV1
What does a FEV1/FVC ratio of <0.7 indicate?
airway obstruction
obstruction tends to cause?
resistance to airflow such as asthma or chronic bronchitis
Restriction to airway tends to cause?
Reduced lung capacity caused by fibrosis or insufficient surfactant release
