Alveoli are an vital part of the respiration system whose function it’s  to exchange oxygen and carbon dioxide molecules to and from the bloodstream. Those tiny, balloon-shaped air sacs sit down at the end of the respiration tree and are arranged in clusters for the duration of the lungs.
           You’ve got approximately 480 million alveoli, located at the end of bronchial tubes. When you breathe in, the alveoli expand to inhale oxygen. While you breathe out, the alveoli  exhale carbon dioxide.
Alveoli ,Bronchi and alveoli , Alveoli structure


Alveoli are tiny balloon formed systems and are the smallest passageway in the respiration system. The alveoli are simplest one cellular thick, permitting the relatively easy passage of oxygen and carbon dioxide (CO2) between the alveoli and blood vessels referred to as capillaries.
One cubic millimeter of lung tissue consists of around 170 alveoli. At the same time as the total range can range from one person to  another, there are literally thousands and thousands inside the human lungs spanning a surface area of roughly 70 squares meter .

Alveoli gas exchange

Gas alternate takes region inside the millions of alveoli within the lungs and the capillaries that envelop them. Inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide movements from the blood in the capillaries to the air within the alveoli.
The overall process involve in breathing
# Moving air in and out of lungs (ventilation )
# Exchange of oxygen and carbon dioxide (diffusion )
# Pumping blood through lungs ( perfusion )

  • Types of Alveoli

  • Types I
  • Pneumocyte  are the cells that are responsible for the exchange of oxygen and carbon dioxide.

  • Type II
  • Pneumocyte perform two essential functions. They are responsible for repairing damage to the alveolar lining and also secrete surfactant .

Functions of Alveoli

  • The characteristic of the alveoli is to get oxygen into the blood circulate for transport to the tissues, and to remove carbon dioxide from the blood circulation.
  • Within the lungs, air is diverted into smaller and smaller microscopic branches referred to as breathing bronchioles, which connect with the alveolar ducts.


  • Chronic obstructive pulmonary disease ( COPD)
Airway obstruction from damaged alveoli walls .Damage to the alveoli causes them to break down ,reducing surface area available for gas exchange .
  • Asthma
Inflammation narrows your airways and block them .
  • Idiopathic pulmonary fibrosis
The walls surrounding the alveoli become scarred and thickened.
  • Lung cancer
Cancer can start in alveoli.
  • Pneumonia
The alveoli fill with fluid , limiting  oxygen intake .
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