Why Does Rigor Mortis Set In After…?

Rigor in Latin means “stiffness,” and mortis means “of death.” But why does the body of a person or an animal get stiff after death, and what causes it? Interestingly, there is a specific physiological process playing out, even when all life is gone.

Right after death, the body’s muscles don’t just stop working instantly. To understand this, one has to take a look at what is going on with the anatomy and physiology of the body.

Muscles in the body are made up of smaller and smaller distinct parts. They are composed of muscle fibers that are bundled into a fasciculus, and a number of these fasciculi make up a muscle. Taking it down to the micro-level, the muscle fibers are made up of myofibrils, and within these myofibrils are even smaller strands called myofilaments. The myofilaments are made up of two protein filaments called actin and myosin, which sit next to each other. These are the sources of a muscle contraction.

A muscle contraction at this level happens when myosin attaches to actin after calcium is released into the cell space. After a chemical reaction, the myosin “ratchets” or pulls on the actin filament. This is also known as the power stroke. The myosin and actin are attached, and in order to repeat the process, something has to come along to detach the myosin from the actin. This is where an important energy…