Filtration of the lungs is a good thing, this is what they are supposed to do.
They get rid of carbon dioxide and replace it with the oxygen that we need, so if you're doctor mentions filtration of the middle lobe of your lung, this is normal.
The "middle lob" is simply the medical term for a section of the right lung.
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The gases enter the blood and are pumped to the heart which then sends it back out to the lungs as we exhale. The lungs filter all the impurities so that we stay healthy.
The lungs are divided into different parts by fissures. The right lung has three parts:
- Superior lobe
- Middle lobe
- Inferior lobe
The left lung has only two parts:
- Superior lobe
- Inferior lobe
The middle lobe is not present on the left side because part of the heart fits into this 'space'.
The middle lobe has the same purpose as the other lobes, they all contain branches of alveoli and filter air whilst providing the necessary oxygen to the blood.