1. the -ve intrapleural pressure is preventing the lung from collapsing.if the pleural pressure became equal to the atm. Pressure,the lung would recoil and collapse

thatís okay but how?I canít imagine..what makes negative pressure prevent lung from collapsing?this is going over my head.

  1. Each elastic structure has a volume where itís neither stretched nor compressed.

This volume is called relaxation volume.
If the relaxation volume of the lungs is 1 litre and that of the thoracic wall is 5 litres
Then at the end of normal expiration when all respiratory muscles are relaxed ,the volume of lung and thoracic wall equals 2.3 litres
I donít understand this at all Can you explain it for me?

  1. What is meant by the surface tension of the fluid lining the alveoli? And how does this tension make the alveoli tend to shrink?
  2. Do Intrapleural pressure changers during inspiration and expiration precede lung volume changes?how
  3. Work required to expand the lungs against the lungs and chest wall elastic forces is called ďcompliance or elastic workĒ

Oh thatís horrible..why against chest wall elastic forces?I know that chest has a continous tendency to expand outwards.

  1. How is the resistance of medium sized bronchi greatest ?greater than resistance of small bronchioles?oh man you must be kiddin me
  2. What makes fall in PCO2 cause bronchoconstriction?
  3. ďEven following a maximum expiration , some air is left in the lungs and air ways because the negative intrapleural pressure prevents complete collapse of the lungs. This air aerates blood between breaths and hence prevets marked changes in blood PCO2 and PO2Ē

Exaplain this please
People Iím feeling so stupid when I started reading about pulmonary ventilation in my text book ..
I canít understand all of this at
Thanks in advance