The adult human body is often said to be about 60% water on average, but that figure varies enormously by tissue. Which pairing below correctly ranks two tissues by their water content?
- Bone contains more water than the lungs
- The lungs contain more water than bone
- Tooth enamel and lung tissue contain almost exactly the same amount of water
- Bone contains no water at all
Why B? And why not the others?
Correct answer: B. The lungs contain more water than bone
A landmark 1945 body-composition study found that water content differs enormously by tissue: lung tissue is about 83 percent water by weight, among the most water-rich tissues in the body, while bone, dense with mineral crystal and structural collagen, is only about 31 percent water, among the least. That gap is exactly why a single 'the body is 60 percent water' figure is a population average that conceals huge tissue-to-tissue variation. Reversing the pairing gets the ranking backwards, since bone is the drier tissue of the two, not the wetter one. Tooth enamel is even drier than bone, built almost entirely of mineral crystal with no blood supply, so it comes nowhere close to matching a fluid-rich organ like the lungs. Bone is not literally waterless either; its mineral matrix still traps a meaningful fraction of water, just far less than soft, blood-perfused tissue holds.
Source: Mitchell, Hamilton, Steggerda & Bean (1945), Journal of Biological Chemistry: The chemical composition of the adult human body and its bearing on the biochemistry of growth