Rigor mortis

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

Stages of death
Pallor mortis Algor mortis Rigor mortis Livor mortis Putrefaction Decomposition Skeletonization
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Rigor mortis (Latin meaning "stiffness of death") is one of the recognizable signs of death that is caused by a chemical change in the muscles after death, causing the limbs of the corpse to become stiff and difficult to move or manipulate.^[1] In humans it commences after about 3 hours, reaches maximum stiffness after about 7 hours, and gradually dissipates until approximately 72 hours (3 days) after death.^{[citation needed]} Heat sources such as fire can speed up the process of rigor mortis.

Biochemistry

After death, cellular respiration in organisms ceases to occur, depleting the corpse of oxygen used in the making of Adenosine triphosphate (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]

Unlike in a normal muscle contraction, after death 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. As part of the process of decomposition, the myosin heads are eaten off by bacteria, allowing the muscle contraction to release and the body to relax.^[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.^{[citation needed]}

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 carcasses, 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.^[4]

Application in forensic pathology

The degree of rigor mortis may be used in forensic pathology to determine the approximate time of death.^[5]

See also

• Cadaveric spasm
• Postmortem spasm

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
4. ^ "Carcass electrical stimulation to prevent cold shortening toughness in beef", DAVEY, GILBERT, CARSE, Meat Industry Research Institute of New Zealand, 1975 via Google Books
5. ^ "Estimating The Time of Death". ExploreForensics. http://www.exploreforensics.co.uk/estimating-the-time-of-death.html. Retrieved 2010-02-09. 

• 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