Rigor mortis

Rigor mortis is the permanent semi-contraction of skeletal muscle after death. It causes the body to become extremely 'stiff' and 'rigid'. The length of time that rigor mortis lasts for is dependant on environmental factors, for example temperature, but typically lasts for around 70 hours. Rigor mortis happens for two reasons, firstly because ATP supplies run out and secondly because calcium ions are not being pumped out of the sarcoplasm. These two factors mean that the 'cross-bridges' between the myosin heads and actin filaments in skeletal muscle cannot break, and thus the muscle is unable to relax. Rigor mortis ends when lysosomal enzymes have broken down the Z lines and titan filaments.