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A) Tiny air sacs in the lungs where gas exchange occurs.
B) Small muscles that control breathing rate.
C) Blood vessels that carry oxygen-rich blood.
D) Airways that transport air to the lungs.
Correct Answer:
Explanation:
Alveoli are small, balloon-like structures located at the ends of bronchioles in the lungs. They are sites where the gas exchange between oxygen and carbon dioxide takes place. This is where the oxygen enters the bloodstream and carbon dioxide leaves it.
An average adult has enough alveoli that if they were to be spread out, they would cover a surface area of 70 square meters (750 square feet). That's almost equal to that of a single tennis court.
Alveoli are coated with a soap-like substance surfactant, which reduces tension when we breathe. This soap-like substance stops the alveoli from collapsing when we breathe. Without it, we wouldn't be able to breathe at all. Premature babies often have trouble breathing as their lungs haven't developed enough surfactant.
We humans have approximately 300 million alveoli in our lungs. That's more population than the 4th most populated country Indonesia, which has 284 million people. It's even more shocking when you realize that a single human has almost the same amount of alveoli as the USA’s total population (345 million).
Although we are born with 300 million or so alveoli, they don't last till our lives end. They start to die or lose their functionality as we age. After 30 we start losing 1% of our lung capacity on average per annum.
Smoking has permanent effects on alveoli as they become less elastic with them. Some conditionals like emphysema and alveoli lose their ability to stretch and hence can't effectively perform their job of transferring gases. The worst part is the damage on these are permanent and cannot be regenerated,
Alveoli and major parts of our lungs possess self-cleaning abilities to certain extents. Cilia and macrophages can filter out dust, pollutants, mucus, and some unneeded parts from the lungs. Though it can only be done in a limited amount. Excessive smoking and high air pollution can still adversely affect it.
At higher altitudes, the air has less oxygen. That means the alveoli have to work extra to extract a sufficient amount of oxygen from the air. However, with regular exposure, the body's red blood cell production will pick up and resolve the issue.
