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Lung Alveolus Structure – Lung Alveoli Anatomy

A magnified view of an alveolar sac

A magnified view of an alveolar sac

  • About 95% of the alveolar surface consists of simple squamous epithelial image descriptiontype I cells, and the remaining 5% is occupied by image descriptiontype II cells (or septal cells).
Zoom in view of a lung alveolus
Simple squamous epithelial type I cells
Simple squamous epithelial type 2 cells
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  • These large, rounded cells are located between the type I cells and  image descriptionsecrete the pulmonary surfactant. The complex of phospholipids and proteins in the surfactant reduces surface tension inside the alveoli, which keeps the alveolar walls from sticking together as they deflate during exhalation.
  • Small openings called image descriptionalveolar pores perforate the interalveolar wall and allow air to pass between alveoli. They provide alternative routes to and from the alveoli if an obstruction occurs.
Zoom in view of a lung alveolus
Small openings called alveolar pores perforate the interalveolar wall
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  • A network of image descriptioncapillaries and many supportive collagen and elastic fibers are found in the narrow interstitial spaces that separate the alveoli.
Zoom in view of a lung alveolus
A lung alveolus demonstrating the network of capillaries
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  • Numerous image descriptionmacrophages (or dust cells) protect the lungs from damage. click  image descriptionhere to see a histological demonstration of the alveoli
Zoom in view of a lung alveolus
A lung alveolus with a macrophage labeled
Microscope slide demonstrating the capillary, type 1 cell, type 2 cell and macrophage
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  • Macrophages (dust cells) image descriptionmove about the air spaces and between the alveoli, where they remove (engulf) inhaled particles, foreign invaders, and other types of harmful substances.

An Overview of the Structure of a Lung Alveolus:

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