Rigor mortis (Latin : rigor stiffness, mortis of death) is one of the recognizable signs of death, caused by chemical changes in the muscles after death, causing the limbs of the corpse to become stiff and difficult to move.
This is gradual stiffening of skeletal muscles that begins from few to several hours after death and reaches a maximum after about 12 hours. The muscles contractand become rigid even without action potentials. The ATP
concentration in cells including muscle cells, declines after death because the nutrients and oxygen, the metabolic
pathways required to form ATP are no longer supplied by the circulation. In the absence of ATP, the breakage of the
link between actin and myosin does not occur. The thick and thin filaments remain bound to each other immobilized
cross bridges, producing a rigid condition in which the thick and thin filaments cannot be pulled past each other.
The stiffness of rigor mortis disappears gradually after about 24 hours as the muscle tissue decomposes, which
presumably results from autolysis caused by lysosomal enzymes.
All these events occur more rapidly' at higher temperatures,The factors that affect onset of rigor mortis include ambient temperature, individual's age, sex, physical condition and muscular build. Rigor mortis may not be perceivable in many infant and child corpses due to their smaller muscle mass The degree of rigor mortis may be used in forensic
pathology to determine the approximate time of death. Rigor mortis is also very important in meat industry. The onset of rigor mortis and its resolution, partially determines the tenderness of meat.
