Alveoli: Gas Exchange

Flash cards every weekday: / igcsebioflashcards
The alveoli ("many alveoli", "one alveolus") are the sites of gas exchange in the lungs. They are tiny air sacks sometimes described as being cauliflower-shaped. Oxygen diffuses across the lining of the alveoli and blood capillaries into and into red blood cells. Carbon dioxide diffuses from the blood to the alveoli. A concentration gradient is maintained by breathing as well as blood flow.
The main adaptation of the gas exchange surface are:
1. Large surface area
2. Thin wall
3. Moist lining
4. Good blood supply
5. Good ventilation

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[@theamazingguy150]

Thank you, especially because you explained how the concentration gradient is mantained

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It REALLY helped. Thank you!

[@patsang4507]

Excellent as is the inhalation exhalation video. As a distance learning teacher, thank you!

[@Ghost.Spectrum]

Thanks so much man! I was always scratching my head when I saw words like "diffusion". I knew the basics of gas exchange but wanted to know more. Awesome explanation and very clear for a first semester human anatomy student! I'll try to remember this video in case my anatomy/physiology professor wants to give a more visual representation of gas exchange

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[@np4511]

Hi! what happens if there is a high CO2 concentration in the atmosphere - how will this affect heart rate?

[@Science_Sauce]

SHORT ANSWER: heart rate will increase. LONGER ANSWER: increased carbon dioxide in the air means more carbon dioxide will diffuse into the blood, raising the blood CO2 level. CO2, when dissolved in blood, makes blood more acidic. The brain recognises this drop in blood pH, and sends a signal to the heart to beat faster to try to remove it.

[@np4511]

But I'm slightly confused. If oxygen diffuses into the capillary from the alveoli how does CO2 diffuse into the capillary as well?

[@Science_Sauce]

The diffusion of one gas doesn't prevent the diffusion of another. Under normal circumstances, the blood CO2 level is higher that that in the alveoli, so CO2 would diffuse out of the blood. However, in the example you described where atmospheric CO2 level rises, the concentration in the alveoli would also increase. This would either slow the diffusion of CO2 out of the blood, or result in a change in direction of CO2 movement (if the atmospheric CO2 level became high enough).

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I didn't understand the messy thing about capillaries of pulmonary artery and pulmonary vein with the air sac????

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It's helpful for me in my "Science" studies! In my "Science" book, I read about this "Alveoli" how it works? Then, I learn it practically from you.
Thanks a lot!!!!

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[@ayeshanaseer3210]

name two structure across which oxygen moves from an alveolar cavity into blood capillaries?

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Our teacher played this for us and everyone thought the alveoli looked like ballsacks

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Thanks for that extra info on important features of gas exchage surface

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[@raudri2011]

Great explanation

[@omvirajsoodan9291]

What is important in exchange of gases?

[@comprobardisponibilidad5281]

Still I am confused of the diagram wheather the capillaries present outside the alveoli or inside . Please help me or just explain in simple terms how actually gas exchanged in capillaries

[@Anonymous-ik3sz]

that diagram is very useful
thanks

[@Alexandra-sd4yy]

I have a question at number 5- good ventilation: it is said that the alveolar air is partially replaced with the atmospheric air. How can it be possible? I know about the ventilation of the dead space but i didn't figure out the mechanism of partial atmospheric air replacement yet.

[@Science_Sauce]

I don’t quite understand your question. When you breathe out you decrease the volume in the lungs (and alveoli) and force air out, which is replaced with atmospheric air when you breath in: as you breath in the intercostals move the rib cage up, increasing the volume, and therefore forcing “new” air into the alveoli. Does that help?

[@Alexandra-sd4yy]

Science Sauce the alveolar air is partially replaced with atmospheric air - i don't understand this sentence 🙁

[@Science_Sauce]

When you breathe out, your alveoli don’t completely empty, a portion of the air will remain, so it’s not 100% replaced, only partially replaced

[@Alexandra-sd4yy]

Science Sauce ok 😂 that's pretty logic. I thought it implies the air in the trachea or the rezidual air but it's that simple. Thanks !

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Thank ya

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Pls put some more videos such blood supply to the lungs

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Simply clever.......

[@vincenttelfer4206]

at 2.25 into video, the blood capillary and the lymph capillary run in parallel separated by interstitial fluid

[@d.anielb4661]

We could make an external lung machine for use in emergencies of people suffocating which takes out a patient's blood, oxygenates it and then reintroduces it to the bloodstream so it keeps the patient in stable condition while the airway blockage is extracted?
I don't know, it just came to me.

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its called a ventilator

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