What term describes the stiffening of muscles after death due to chemical changes in body tissues?

• A. Putrefaction
• B. Cadaveric Spasm
• C. Rigor Mortis
• D. Luminal

Answer: (C)

Rigor mortis is the stiffening of muscles after death caused by chemical changes in muscle tissue. After death, cells stop producing energy (ATP), and calcium remains in the muscle cells, allowing myosin heads to stay bound to actin. Without ATP, muscles cannot relax, so they lock in a contracted position. The process starts a few hours after death, often beginning with small muscles (jaw, eyelids) and then spreading to larger groups, reaching maximum stiffness around 12 hours and gradually dissipating over the next day or two as proteins break down. Temperature and other conditions influence timing—the warmer the environment, the faster it develops and resolves. This differs from putrefaction, which is microbial decomposition, and from cadaveric spasm, which is an immediate stiffness at the moment of death due to extreme stress rather than a progressive postmortem change.