rigor mortis

Home » Modern Medicine » Forensics » rigor mortis
rigor mortis2016-12-16T12:28:57+00:00

rigor mortis


A major sign of death in which skeletal muscles acquire a board-like rigidity shortly after death. Rigor mortis–RM first appears in the jaw and other short muscles–e.g., of hand at 2-4 hours after death, later develops in the trunk and extremities, peaks at 24-48 hours, then disappears in the same order as it developed.

Mechanism After death, oxygen and intracellular glycogen are depleted, ATP falls and pH rises precipitously. In the absence of ATP, the SERCA–sarco/endoplasmic reticulum Ca2+-ATPase pump shuts down and calcium ions diffuse from into the sarcomere, binding with troponin and allowing crossbridging between myosin and actin. RM begins at ATP levels of 85% normal and disappears as ATP falls below 15%. The rapidity of onset of RM is related to environmental factors, especially temperature; it occurs more rapidly in hot weather or when accompanied by convulsions, strychnine poisoning, sunstroke and tetanus. It also occurs in cardiac and smooth muscle, affecting vessels and the gastrointestinal and urogenital tracts. It begins earliest in muscles that were most active before death. 

Rule of thumb for rigor

Warm and flaccid   < 3 hours

Warm and stiff       3-8 hours

Cold and stiff         8-36 hours

Cold and flaccid     > 36 hours

Special considerations 

Rigor occurs in the

• Dartos, compressing the testes and epididymis and the muscle fibres of the prostate and seminal vesicles, resulting in expression of semen from the urethral meatus, lending weight to myths of ante-mortem sexual activity

• Arrector pili muscles, resulting in “goose flesh”

• Heart, luring the unwary into overdiagnosing ventricular hypertrophy

• Iris; the pupils may be unequal  

Synonyms Post-mortem corporal rigidity, rigor stiff, stiffness of cadaver

Reference http://en.wikipedia.org/wiki/Rigor_mortis  

Leave A Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.