From: roadkill 19/05/2001 23:38:42
Subject: rigor mortis post id: 303574
Please describe the process of rigor mortis. How long does it take for rigor mortis to set in? Is this permanent or does the body become limp as further decay commences? Thanks, Roadkill

From: pigman 20/05/2001 1:39:04
Subject: re: rigor mortis post id: 303627
Muscle acidification and rigor development

Metabolic activity continues after the pig is slaughtered, but the cessation of the circulatory system results in this occurring under anaerobic conditions. In the short term creatine phosphate is used to phosphorylate ADP to ATP allowing metabolism to continue. When the supply of creatine phosphate is exhausted ATP is created through glycolysis. This breakdown in glycogen results in the subsequent production of pyruvate and the concomitant reduction of NAD+ to NADH. However, in order to maintain homeostasis the accumulated NADH must be re-oxidized. This occurs through the conversion of pyruvate to lactate, resulting in three moles of ATP being synthesized for every mole of NADH oxidized. When the circulatory system is compromised, the lactate cannot be removed and the muscle gradually acidifies (Hedrick et al., 1994), with acidification of the pig normally taking four to eight hours. With this accumulation of lactic acid the pH of the meat lowers. Normally this fall is gradual, reaching about 5.4 to 6.0, 24 hours post-slaughter [Whittemore, 1998. #406].

Rigor will set in and then gradual decline as the carcass ages

From: roadkill 20/05/2001 4:10:01
Subject: re: rigor mortis post id: 303647
Thanks, pigman. Does rigor mortis cease at some stage or is it dependent on stage of body decomposition? How long after death b4 it starts? In my experience it can be a matter of a couple of hours. (Basically, how long has the cat been dead?)

From: Zardoz 20/05/2001 8:58:39
Subject: re: rigor mortis post id: 303675
When a person dies, a stiffening of the body occurs called rigor mortis. This is due to a build up of lactic acid in the body due to a lack of metabolism and the muscles stiffen up. You may have experienced a cramp or "Charlie horse" in a muscle after running or working out. Lactic acid has built up in your muscle and has caused a stiffening of the muscle.

Rigor mortis is temporary; eventually the muscles become flaccid again as decomposition sets in.

Death is divided into two categories, somatic and cellular. Somatic death occurs before cellular death.

Somatic death is the death of the whole body. It is the point at which the body can only be kept alive with the aid of machines. Cellular death occurs when individual cells can no longer metabolise. Different types of cells die at different rates.

After somatic death, muscle cells cease to receive oxygen, or respire aerobically, due to the lack of blood circulation. The muscle cells then use anaerobic respiration to produce energy (ATP) from stored glycogen. One product of anaerobic respiration is lactic acid. Since the blood is no longer circulating, lactic acid cannot be removed from the cells and their pH decreases. This low pH inhibits enzyme activity which controls cellular metabolism. Therefore, the low pH causes muscle cell metabolism to cease.

The time it takes for muscle cell metabolism to cease depends in part on the environmental temperature at the time of death. The higher the temperature, the faster chemical reactions occur causing the cells to produce lactic acid more quickly, speeding cell death. The rate at which muscle metabolism ceases also depends on the initial concentration of lactic acid in the cells at the time of death. For instance, if the circumstances of death invoked the body's fight or flight response, the amount of lactic acid in the muscle cells at the time of death would be increased, resulting in a shorter time for metabolic activity to cease after death.

In determining the time of death, forensic pathologists, among other things, use the incidence of rigor mortis. Rigor mortis is stiffness that is caused in part by the breakdown, after death, of the muscle cell's sarcoplasmic reticulum. This causes calcium ions to be released and to form crossbridges between the myosin and actin filaments. Crossbridges cause muscle cells, living or dead, to contract or become stiff. For muscle cells to relax, energy produced from respiration is required. After somatic death, muscle cells eventually loose their metabolic potential to produce energy and permanent crossbridges are formed. These permanent crossbridges cause the rigor mortis.

The time required to achieve rigor mortis varies with the type of species. Poultry may require only 1 to 2 hours whereas beef is likely to need 20 to 24 hours. For humans in temperate regions, the following is used as a guide to estimate the time of death:

Environment Warm.... Not stiff.... Not dead more than 3 hours
Environment Warm.... Stiff.... Dead between 3 and 8 hours
Environment Cold.... Stiff .... Dead between 8 and 36 hours
Environment Cold.... Not stiff.... Dead for more than 36 hours

As you can see, there are variables that determine how long it takes muscle cells to die.

From: Paul H. 20/05/2001 9:09:24
Subject: re: rigor mortis post id: 303681
If I may summarize using soldier's parlance:

First they're floppies, then they're stiffies, and then they're squishies.


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