What Is Rigor Mortis?

Have you ever wondered what causes rigor mortis?

I have. And here is the answer.

Rigor Mortis occurs after someone dies, causing the body to become rigid (probably the reason dead people are referred to as "stiffs" when they die).

In people, rigor mortis usually begins 2 or 3 hours after death, with the body becoming gradually more rigid over a period of 12 hours. This rigidity then begins to decrease until almost 3 days after death, when rigor mortis has completely dissipated.

Rigor mortis has been observed to progress in a set pattern (Nysten's Law, named after the doctor who observed it in 1812), with the head, face, jaw and neck being affected first, working it's way down eventually to the legs and feet.

Rigor mortis is believed to be a process resulting from a lack of oxygen, with a complex chemical chain reaction leading to the extreme muscular contractions. In this reaction, adenosine triphosphate (ATP) becomes absent. This is important because ATP has a role in relaxing contracted muscle. Rigor mortis gradually dissipates only when the muscle fibres decompose.

Other than an unusual change in the body after death, it is also a useful process in terms of pathologists using the progress of rigor mortis to determine the approximate time of death. Various factors affect the onset and progress of rigor mortis e.g. a warm climate can speed up the process, and a cold climate can slow it down.

Rigor mortis is just one aspect of the whole process of death, but, I'm sure you'll agree, an important one.