What is rigor mortis?

Rigor mortis refers specifically to the postmortem stiffening of the muscles that occurs due to biochemical changes in the body after death. After the death of an organism, the body no longer produces adenosine triphosphate (ATP), which is essential for muscle relaxation. As a result, the muscles remain in a contracted state, leading to the characteristic rigidity associated with rigor mortis. This stiffening usually begins within a few hours after death and can last for several days, depending on various factors such as temperature and the physical condition of the deceased.

In contrast, the other options describe different postmortem phenomena. The cooling of the body after death, known as algor mortis, involves the drop in body temperature as the metabolic processes cease. The settling of blood in the body, termed livor mortis, refers to the pooling of blood due to gravity, which also occurs after death. Finally, the process of tissue decay, known as decomposition, involves the breakdown of cells and tissues over time. Each of these processes represents distinct changes that occur after death, but rigor mortis specifically points to the stiffening of muscles.