What term describes the stiffening of muscles after death?

• A. Rigor Mortis
• B. Hypostasis
• C. Algor Mortis
• D. Livor Mortis

Answer: (A)

Stiffening of muscles after death happens because the body's cells run out of ATP, which normally lets muscles relax. Without ATP, the myosin heads stay bound to actin, locking the muscles in a contracted, rigid state. This lasting tightness is called rigor mortis. It usually begins a few hours after death, starting in smaller muscles like those of the face and jaw, then moving to larger muscle groups, and eventually fades as decomposition progresses over about a day or two.

The other terms describe different postmortem changes. Algor mortis is the body cooling to the surrounding temperature, while livor mortis (also called hypostasis) is the pooling of blood in dependent parts of the body, causing a reddish-purple discoloration rather than stiffness.