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Question: what do you know about the lungs
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Matthew Burgess answered on 3 Jun 2019:
Probably not as much as I should after two years!
The lungs are the site of gas exchange in our bodies. We draw in air as we inhale to obtain the oxygen (O2) that (almost) every cell in our body needs for aerobic respiration (the production of energy/ATP by oxidation of glucose) and exhale the carbon dioxide (CO2) that is produced by that process. To reach throughout our body these gases are carried in our bloodstream and so the lungs are the site where O2 and CO2 move from the air we breath to our blood vessels for distribution.
To transfer the large amount of gas our body needs as large a surface area as possible, so our lungs are like a large upside down tree with lots and lots of branches. From your mouth is your windpipe or trachea. This splits into the left and right bronchus that feed into our left and right lungs. Here these bronchi branch thousands more times until they are much smaller tubes feeding into alveoli. These are small balloon like sacks with walls just one cell thick so that the gases can diffuse across as quickly as possible.
Similarly we want the gases to get in and out of the bloodstream as efficiently as possible so a large artery carries low O2 high CO2 blood that’s been around our body into the lungs and forks thousands of times into capillaries (vessels with very thin walls) and then forms back into a large vein that carries blood with high O2 and low CO2 back to the heart to be pumped back around our bodies.
Muscles in our chest and the diaphragm muscle below relax and contract to expand and compress our lungs to draw fresh O2 rich air in and force CO2 rich air out.
Because these layers of cells are so thin, the lungs could be at especially high risk of infection from pathogens in the air. To combat this special cells in the lung walls produce mucus that traps pathogens but still lets the gasses diffuse across. Epithelial cells that form the lung lining have many pathways to fight against infection and can also release signals to warn their neighbours if they have been damaged or attacked. There are also many types of specialised immune cells in both the lung tissue and the blood that can respond to the pathogens and/or the signals that the damaged cells release to fight off the infections.
Like all the tissues in our body, these defensive mechanisms need to be in careful balance. If too active we can get diseases like allergies and asthma that over time change the structure of the lungs so it is stiffer and thicker, which means it’s less efficient at transferring gases. If it is not active enough we are more likely to catch diseases like colds and the flu and unable to fight them off meaning we can become dangerously unwell.
My work looks at the mechanisms of these defences against infection so that we can design new ways to help us fight lung diseases in those with weak responses or to treat those whose overactive immune responses are damaging their lungs.
Comments
Emma commented on :
I always imagined the lungs to be two sacks, like balloons, but I was so surprised when I finally dissected a sheep lung during my A-Levels and it was more like a sponge with lots of little holes and nothing like I imagined! I think this is because the way science diagrams depict the lungs, it is easier to draw them as large sacks.
There is a very good reason they are similar to a sponge, this is about surface-area. The exchange of gases can only occur when the gas is in contact with the tissue of the lung which is covered in very fine blood vessels, so more tiny holes means more surface area of lung tissue which is in contact with the air to exchange gases. This is why a sponge is good at quickly soaking up water, because lots of its surface is in contact with the water and so can quickly absorb it. The same happens with the gases, meaning they can be quickly exchanged before you breathe out.