rigor mortis

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Muscular stiffening following death.

[Latin : rigor, stiffness + mortis, genitive of mors, death.]

Shortly after death all the muscles in the body become soft and flaccid. At a variable time later, they become firm and rigid. This is known as rigor mortis. Rigor commences in the smallest muscles such as those in the face and the hands, and then extends to the limb muscles. Rigor can be ‘broken’ by stretching the muscle, for example by moving the jaw or the elbow, and does not then return.

Rigor is brought about by a chemical change in the muscle. The normal reaction between adenosine triphosphate and adenosine diphosphate (ATP and ADP) within the muscle fibres, which supplies energy for their contraction during life, ceases and the ATP level in the muscle progressively diminishes. This is accompanied by accumulation of lactic acid and a fall of pH (increase in acidity), which leads to stiffening and firmness. Whether or not the muscle fibres actually shorten has not been established.

Temperature is an important factor in determining the time of onset of rigor. In normal circumstances and at room temperature rigor is complete in about three to six hours. If the temperature is higher the onset is more rapid — perhaps no more than an hour in tropical temperatures. Conversely, the onset of rigor is delayed at low temperatures. In cases of drowning in cold water, for example, rigor may not appear until the body has been removed from the water, even after several days of immersion. The onset of rigor is hastened if there has been intense physical activity shortly before death. Thus, in forensic medical practice, the presence of rigor is a poor determinant of the time of death. Once established, the duration of rigor ranges from 18 to 36 hours.

— J. Hume Adams

See also corpse; death.

Stiffening of muscle that occurs after death. As the flow of blood ceases, anaerobic metabolism leads to the formation of lactic acid and the soft, pliable muscle becomes stiff and rigid. If meat is hung in a cool place for a few days (‘conditioned’), the meat softens again. Fish similarly undergo rigor mortis but it is usually of shorter duration than in mammals. See also DFD meat; meat conditioning.

The stiffening of skeletal and cardiac muscle shortly after death.

Lat: medical terminology depicting the stiffness, numbness, or hardness of the muscles, that occurs after death. Assists the coroner in determining time of death.

Stiffening of the muscles of the body that occurs after death. Rigor mortis is Latin for “stiffness of death.”

This article is about the sign of death. For other uses, see Rigor mortis (disambiguation).

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Signs of death
Pallor mortis Algor mortis Rigor mortis Livor mortis Decomposition Skeletonization
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Rigor mortis is one of the recognizable signs of death (Latin mors, mortis) that is caused by a chemical change in the muscles after death, causing the limbs of the corpse to become stiff (Latin rigor) and difficult to move or manipulate.^[1]

Contents 1 Biochemistry 2 Applications in Industry 3 References 4 See also

Biochemistry

After death, respiration in organisms ceases to occur, depleting the corpse of oxygen used in the making of ATP. ATP is no longer provided to operate the SERCA pumps in the membrane of the sarcoplasmic reticulum, which pump calcium ions into the terminal cisternae.^[1] This causes calcium ions to diffuse from the area of higher concentration (in the terminal cisternae and extracellular fluid) to an area of lower concentration (in the sarcomere), binding with troponin and allowing for crossbridging to occur between myosin and actin proteins. ^[2]

The body may only move, after Rigor Mortis has set in, if put into a below freezing temperature, and forty-five minutes later switched to a higher temperature. Repeat this cycle to get the muscles moving.^{[citation needed]}

Unlike normal muscle contractions, the body is unable to complete the 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.^[1][3]

Applications in Industry

Rigor mortis is very important in meat technology. The onset of rigor mortis and its resolution partially determines the tenderness of meat. If the post-slaughter meat is immediately chilled to 15°C (59°F), a phenomenon known as cold shortening occurs, where the muscle shrinks to a third of its original size. This will lead to the loss of water from the meat along with many of the vitamins, minerals, and water soluble proteins. The loss of water makes the meat hard and interferes with the manufacturing of several meat products like cutlet and sausage.

Cold shortening is caused by the release of stored calcium ions from the sarcoplasmic reticulum of muscle fibers in response to the cold stimulus. The calcium ions trigger powerful muscle contraction aided by ATP molecules. To prevent cold shortening, a process known as electrical stimulation is carried out, especially in beef carcass, immediately after slaughter and skinning. In this process, the carcass is stimulated with alternating current, causing it to contract and relax, which depletes the ATP reserve from the carcass and prevents cold shortening.

References

1. ^ ^{a b c} About.com
2. ^ http://www.howstuffworks.com/muscle.htm
3. ^ http://www.newton.dep.anl.gov/askasci/zoo00/zoo00248.htm

• Bear, Mark F; Connors, Barry W.; Paradiso, Michael A., Neuroscience, Exploring the Brain, Philadelphia : Lippincott Williams & Wilkins; Third Edition (February 1, 2006). ISBN 0781760038
• Robert G. Mayer, "Embalming: history, theory, and practice", McGraw-Hill Professional, 2005, ISBN 0071439501

See also

• Cadaveric spasm
• Postmortem spasm

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