Rigor mortis occurs when a bod

Rigor Mortis is a temporary condition after death, which ischaracterised by stiffening of the muscles and it happens due tolack of ATP generation.

Cellular respiration is aimed to generate ATP. ATP plays thecentral role in regulating the muscle contraction andrelaxation.

Muscle contraction happens in different stages beginning fromgeneration of action potential and finally to the formation ofcross bridging between actin and myosin filament. Calcium ions alsoplays the important role in promoting muscle contraction. Incontracted state the muscle is stiffened and is characterised bycross bridging of actin and myosin filament. ATP is the onlymolecule which is able to break this cross linking and to releaseMyosin from actin.

In muscles ATP can be produced by three pathways

Aerobic respiration

Glycogen – lactic acid system

Creatine Phosphate – creatine Kinase system.

Among all these pathways ATP generation is maximum in theaerobic respiration and is the major one. But when death happensthis pathway ends and muscle will depend on the other two pathwaysfor ATP generation. But the generation of ATP is very less anddepleted fast in these alternative pathways. Thus due to lack ofATP generation muscle are not able to relax . At the same time thecells fails to identify the death and there is continuous releaseof calcium ions from sarcoplasmic reticulum which also promotemuscle contraction and rigor Mortis.

This contracted state of muscle is a temporary condition becausethe continuous generation of lactic acid in the body by anaerobicrespiration after death will reduce the body pH and will decay ordetoriate the muscle.

To conclude, rigur mortis can be defined as temporary stiffeningof body muscle due to muscle contraction , which is happening dueto absence of ATP which is necessary to relax the muscle bybreaking actin myosin cross linking.