Pneumocytes
Pneumocytes (or alveolar cells) are the cells that line the alveoli and comprise of the majority of the inner surface of the lungs
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There are two types of alveolar cells – type I pneumocytes and type II pneumocytes
Type I Pneumocytes:
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Type I pneumocytes are involved in the process of gas exchange between the alveoli and the capillaries
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They are squamous (flattened) in shape and extremely thin (~ 0.15µm) – minimising the diffusion distance for respiratory gases
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The cells are connected by occluding junctions, which prevents the leakage of tissue fluid into the alveolar air space
Type II Pneumocytes:
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Type II pneumocytes secrete pulmonary surfactant, which reduces surface tension in the alveoli (making it easier for them to inflate)
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They are cuboidal in shape and possess many granules called lamellar bodies (which store the surfactant)
Types of Alveolar Cells
