Which tissue can survive the longest without oxygen?

• A. Muscle
• B. Heart
• C. Liver
• D. Kidneys

Answer: (A)

The key idea is how long a tissue can keep functioning when oxygen runs out, which depends on how much ATP it can generate without oxygen and how much oxygen it normally requires. Skeletal muscle can endure longer periods without oxygen because it has sizable glycogen stores and can switch to anaerobic glycolysis to make ATP when oxygen is scarce. Its baseline energy demand is relatively modest when it’s at rest, and it can sustain ATP production for a longer time despite accumulating lactic acid. In contrast, heart muscle depends almost entirely on oxygen-driven oxidative phosphorylation and must keep pumping continuously, so oxygen deprivation rapidly impairs its contractile function. The liver and kidneys do experience hypoxia, but neither outlasts skeletal muscle in a hypoxic situation: kidneys are quite vulnerable due to high metabolic activity, and the liver, though tolerant to some extent because of its dual blood supply, still declines with sustained oxygen lack. So skeletal muscle is best able to survive the longest without oxygen.