How many alveoli does lungs contain?

Hint: In your lungs, alveoli are tiny air sacs that soak up the oxygen you inhale and keep the body moving. Though they are microscopic, the workhorses of your respiratory system are the alveoli.

Complete answer:
You've got roughly 480 million alveoli at the end of the bronchial tubes. The alveoli stretch to take in oxygen as you breathe in. The alveoli shrink to remove carbon dioxide when you breathe out.

Your breathing requires three general processes:
1.In and out of the lungs, transferring air (ventilation)
2.An exchange of oxygen-carbon dioxide (diffusion)
3.Blood pumping into your lungs (perfusion)

Although small, the alveoli are the source of the gas exchange for your respiratory system. The alveoli absorb the incoming energy (oxygen) you breathe in and release the carbon dioxide (outgoing waste product) you exhale.

Your blood absorbs the oxygen from the alveoli and releases carbon dioxide to the alveoli as it passes through blood vessels (capillaries) in the walls of the alveoli.

All together these tiny alveoli structures form a very wide surface area to do your breathing function, both when you're at rest and when you're exercising. The alveoli cover a surface of over 1,076.4 square feet (100 square meters).

To process the enormous quantities of air involved in breathing and bringing oxygen to your lungs, this broad surface area is required. Around 1.3 to 2.1 gallons (5 to 8 litres) of air every minute is taken in by the lungs.

Your diaphragm and other muscles help build pressure inside your chest in order to force the air in and out. Your muscles produce a negative pressure as you inhale, less than the ambient pressure that helps to draw air in. The lungs recoil and return to their usual size as you breathe out The alveoli are organised into bunches, grouping each bunch into what's called the alveolar sac.

The epithelium, the outer layer of alveoli, is composed of two cell types: type 1 and type 2.
Alveoli cells of type 1 occupy 95 percent of the alveolar surface and form the barrier to air-blood.
Type 2 alveolar cells are smaller and are responsible for creating the surfactant that covers the alveolus' inside surface and helps reduce the stress of the surface. When you breathe in and out the surfactant helps preserve the form of each alveolus. Type 2 alveolar cells may also transform into stem cells.

Note: The almost perfect Alveoli breathing machine can break down or become less effective because of:
1.Sickness
2.Normal ageing,
3.Smoking and Air Pollution