original art: Elizabeth Figgie: Our lungs have, on average, 274-790 million pulmonary alveoli (in zeroes, that’s 790,000,000) through which our lungs and bloodstream exchange oxygen and carbon dioxide. The alveoli seem vulnerable in that their surface is a single-cell thick, but that vulnerability allows them to readily make this exchange with blood capillaries (their endothelial layer also one cell […]