What is rigor mortis?

• A. Stiffening of muscles after death
• B. Drying of skin after death
• C. Cooling of body after death
• D. Swelling of brain after death

Answer: (A)

Rigor mortis is the stiffening of the body's muscles after death. It happens because ATP, which normally helps muscles relax by letting the myosin heads detach from actin, is no longer produced once life ends. Calcium ions flood the muscle cells and cause actin and myosin to form cross-bridges, but without ATP to detach them, the muscles stay in a contracted state. This stiffness typically starts a few hours after death, often in smaller muscles like the jaw or neck, then moves to larger muscle groups, and lasts until enzymatic processes gradually break down the muscle proteins as decomposition progresses. Temperature affects how quickly it develops and dissipates. This change is different from drying of the skin, cooling of the body, or swelling of the brain, which are other postmortem changes.