Lecture 4 – Respiration III

Reticular network is highly important in determining

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Reticular network is highly important in determining the elastic recoil of the lungs  in breathing in/out Adult humans have about 300 million alveoli Pattern of Branching Long big pipes connecting to shorter and narrower pipes You have to have the same amount of flow at each level Only way you can get the same amount of flow is if you apply a different amount of  pressure and change the conductance Consequences of Equal Flow Flow through any level has to equal the flow at the next level Flow is the conductance times the pressure gradient You have to increase the number of tubes AND the total cross sectional area You have to have smaller lengths to make sure that the conductance is not too small In the respiratory tree, there are ~23 sets of tubes in series The pressure gradient is the driving gradient pulling the air into the lungs Equal to the sum of all the pressure gradients as you go down the pipes The pressure gradient must be generated by muscle contraction (by changing Palv) so  that all the pressures are kept small Change the volume of the thoracic cavity, which changes the volume of the lung Remember than conductance is proportional to radius^4/length As tube diameters get smaller, the shorter lengths re require to keep the conductance  high Increased cross-sectional area is accomplished by having many tubes Large cross section al area compensates for high resistance to maintain flow
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Area and resistance in the bronchial tree The resistance to flow in the airway generation is which/how many branching points  have happened In the terminal bronchioles there is almost no resistance because the distance is really  short and the conductance is high (surface area is high)
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