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. Author manuscript; available in PMC: 2021 Oct 11.
Published in final edited form as: Curr Opin Biomed Eng. 2019 Nov 13;11:130–136. doi: 10.1016/j.cobme.2019.11.003

Figure 1.

Figure 1

The lungs embody a highly complex organ with a vast dichotomously bifurcating asymmetric tree structure that spans over three orders of magnitude in anatomical length scales, that is, from centimeters in the trachea down to ~100 μm alveolar cavities in the depths of the acinar regions. Its surface area available for gas exchange, and consequently aerosol delivery, is approximately 100 m2 for an average human adult (i.e., the size of a tennis court), with >106 m of pathways and nearly half a billion alveoli.