RIGOR MORTIS in detail. prepared by Dr.RAJKUMAR MALUR.
Text of RIGOR MORTIS by rajkumar malur
PG IN FORENSIC
Prof . &HOD
DEPT. OF FORENSIC
Rigor mortis (Latin: rigor "stiffness", mortis "of death")
Also called as DEATH STIFFENING,CADAVERIC RIGIDITY
RM is one of the recognizable signs of death, caused by Physiochemical changes in the muscles(voluntary+involuntary) after death, causing the limbs of the corpse to become stiff ,shortening of muscle fibres.and difficult to move or manipulate .
In humans, it commences after about two to six hours, reaches maximum stiffness after 12 hours, and gradually dissipates from approximately 24 hours after death. Depending on temperature and other conditions, rigor mortis lasts approximately 72 hours.(Rule of 12).
cessation of respiration
depletion of oxygen used in making of ATP
ATP no longer provided to operate the SERCA pumps in the membrane of the sarcoplasmic reticulum,which pump calcium ions into the terminal cisternae
calcium ions diffuse from the terminal cisternae and extra cellular fluid to the sarcomere
Calcium binds with Troponin
Crossbridging between myosin and actin filaments.
Unlike normal muscle contractions,the body is unable to complete cycle and release the coupling between the myosin and actin,creating a perpetual state of muscular contraction,until the breakdown of muscle tissue by digestive enzymes during decomposition.
Signal from NERVOUS SYSTEM to contract MUSCLE
Myosin-Thick filament/ATP dependent
Actin-Thin filament/Contractile filament
Of muscle cells.
Thick filaments- Myosin are anchored to M line(center)
Actin filaments are anchored to outer edge of Sarcomere-Z Line
Myosin pulls Actin filaments along its length:
Sliding filament mechanism:
Lengths of filaments do not change
Causes shortening of muscle fiber and muscle
SUPPLY OF ATP IN MUSCLES DURING LIFE:
1. Phosphagen System
2. Glycogen-lactic acid system
3. Aerobic system.
ATP is responsible for elasticity and plasticity of muscle during life.
ATP hydrolysis=ADP+Inorganic phosphate
*Hydrolysis energy=>Power stroke action of Myosin.
Muscle contractions are controlled by Calcium ions
At RELAXED STATE:
Tropomyosin blocks CROSSBRIDGES,
Regulatory Proteins on Actin :TROPONIN and TROPOMYOSIN
When calcium levels are high enough and ATP is present ,
Calcium binds to Troponin and displaces Tropomyosin and
Helps in formation of Cross bridges.
Signal from Nervous system to CONTRACT=>Calcium
Released from sarcoplsamic reticulum.
Z-Lines draw close to M –Lines=shortening of muscle fiber
Rigor mortis -VIDEO
PHYSIOCHEMICAL CHANGES IN MUSCLE
ATP is progressively and irreversibly destroyedaccumulation
of lactates and phosphates in muscles.
No Resynthesis of ATP
Postmortem SARCOPLASMIC DISRUPTION Flooding of
Calcium Ions into SARCOMERES Initiating the binding of
Actin and Myosin MIMICKING NORMAL CONTRACTION.
Rigor Mortis sets in when ATP is reduced to a critical level(85% of
-normal).Rigidity is MAXIMUM when ATP depletion is 15%.
Rigormortis is lost when putrefaction starts Proteolytic detachment
Loss of Structural Integrity muscles soften and relax.
ORDER OF APPEARANCE:
Nysten’s Rule:Rigormortis does not start in all muscles
Shapiro(1950):Rigormortis mostly likely to develop
simultaneously in all muscles.smaller muscles>larger.