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    In healthy lungs, a gradient is maintained between the concentration of oxygen in the lavoli and the concentration of oxygen in the lung capillaries.

    1.Describe how ventilation helps to maintain this difference in oxygen concentration.
    2.Give one other way that helps to maintain the difference in oxygen concentration.

    Why not try having a go first and posting your ideas so we can help you, rather than just dumping the question and expecting people to do your homework for you (which no-one will)?

    You ask the Q because you are struggling, so let me teach you how you go about solving a problem like this:

    1. First what is ventilation? - OK in simple language: breathing - are you with me? OK good. Next, what happens in the alveoli? - yes yes good the Q tells you: gas exchange - how? by diffusion - correct! - OK from GCSE chemistry what %age of air (which you are breathing in) is oxygen? Remember: yes well done 20% roughly.

    This oxygen is being taken up by the blood in the capillaries surrounding the alveoli - yes? Remember Sir or Miss explaining that in class? Cool! So if oxygen is being taken out of the air in the alveoli into the blood AND you are bringing in new air with of course higher %age of oxygen by breathing....................... ................................ ...............of course, that will keep the %age of oxygen in the alveoli high all the time i.e. greater than in the blood which is flowing (why? yes due to heart beating - good) and carrying it away: agreed? OK YOU HAVE YOUR ANSWER - this explains why the DIFFERENCE IN OXYGEN CONC-N IS MAINTAINED by breathing (=ventilation).

    2. The last two lines (in bold) tell you, don't they? On the alveoli (air in lungs) side, more O2 is brought in by breathing - What else could be done to maintain the difference? - yes, you could reduce i.e, make less the other side = O2 %age in the blood - How? yes, by carrying the oxygen taken into the blood away from the alveolar capillaries - all makes sense, doesn't it? How exactly? Of course, by having a good blood circultion, which we know the alveoli have - millions of tiny, highly branched capillaries!

    Now I m sure you will agree with me:............................. EASY PEASY, Lemon Squeezy!! (sorry, taking you back 10 years )

    Enjoy biology - learn to work it out - NOT A THICK BOOK TO MEMORIZE!

    Mukesh (Specialist Biology Tutor)
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