Lihasjäikuse

Lihasjäikuse, also known as muscle stiffness or rigor mortis, is a post-mortem condition affecting the muscles of a deceased individual. It is characterized by a temporary rigidity of the muscles, which typically appears within two to six hours after death. This rigidity is caused by a biochemical process involving the depletion of adenosine triphosphate (ATP), a molecule essential for muscle relaxation.

When an organism dies, cellular respiration ceases, and ATP production stops. ATP is normally responsible for breaking the bonds between actin and myosin filaments in muscle fibers, allowing them to detach and the muscle to relax. Without ATP, these bonds remain formed, leading to a state of sustained muscle contraction. This process is not an active contraction but rather a passive stiffening.

The onset and duration of lihasjäikuse are influenced by several factors, including the ambient temperature, the individual's physical activity level before death, and the cause of death. In warmer environments, the process tends to occur and resolve more quickly due to accelerated enzymatic activity. Conversely, in colder conditions, it may develop and persist for longer periods. Lihasjäikuse typically begins in the smaller muscles, such as those in the face and neck, and then spreads to the larger muscles of the limbs and trunk.

Eventually, lihasjäikuse subsides as the muscle proteins begin to decompose. This decomposition process, driven by enzymes released from lysosomes within the muscle cells, breaks down the actin and myosin filaments, thereby releasing the bonds that caused the stiffness. The resolution of lihasjäikuse usually occurs within 24 to 48 hours after death, depending on the same factors that influence its onset. The presence and stage of lihasjäikuse are often used in forensic investigations to help estimate the time of death.