What is the physiological & pathological explanation for rigor mortis?

Is this homework?

Rigor mortis Is an intravascular postmortem response to the cellular death of the body. It sets in at about 3 to 4 hours after death. Then releases from the body at about 36 to 72 hours after
You can releve rigger by flexing, rotating, massaging, and starching. Some forms of Rigger are more advanced to others. It depends on decomp and if the body has been cooled. The blood in the body goes to a liquid state when cooled witch slows down decomp.
All effect rigger.

I'll tell you where to look but no more!
Look at the acting myosin head cross bridge cycle. Take note of the role of ATP, think about how ATP is produced in the cell and what is required for it's production. Then think about what happens in death- where does the cycle get stuck and why?

You should be able to piece together the explanation from that.

Random tip if you are doing a biology course and they are asking questions such as that you will probably be tested on the cross bridge cycle so it is worth learning off by heart :)

What do you mean where do the cycle get stuck.

Right here is a link to an animation of the cross brigde cycle also known as the sling filament theory. It doesn't describe it as a cycle here but it was the only working animation I could find. Mechanism of Filament Sliding
Here's a diagram so you can see it as a cycle.
Google Image Result for http://mednote.co.kr/PHYSIOLOGYBLUE/xbcycle.gif

When I mean stuck I am referring to it no longer being able to progress because an important component is missing.

I don't understand how this has to do with Rigor Mortis

Right I see you are a funeral director, so you have a broad system idea of rigor mortis, I am a biochemist so I am trying to nudge the person in the right direction for the biochemical explanation. You described it very well but didn't explain why it happens, the physiological explanation.

If you understand how a muscle contracts then you can understand why it doesn't relax in death and instead stays contracted and makes the body rigid. That is usually the point in asking the OPs question, as a test in understanding at the end of a course on muscles.

Ok I found the site you gave very interesting. I was glad that I had a chance to read it. Thank you. If he does not use it, I did.

Rigor Mortis is a very beautiful thing! A body stops working, and 2 - 3 hours later it starts Rigor Mortis. The first is Putrefaction. This usually begins in the large intestine, read about Putrefaction.
The body slowly goes through Rigor Mortis, where the muscles stiffen. It reaches it's peak at about 12 hours after the beginning, and then reverses. When you have Rigor Mortis at its peak, if you try to move the body, it will just break.
At the end of Rigor Mortis the body starts decaying. The skin shrinks a little, it can made finger nails look longer then they were!
Rigor Mortis usually lasts 24 - 48 hours, but a lot has to do with the place the body is.
Look up the Body Farm. It is a beautiful place that is great with knowledge on Rigor Mortis and decomposition.

The body does not break OH MY GOD!! The peak it does not have a peak it depends on the body and cause of death. Rigor lasts 48 to 72 hours. The body by the way starts decomposition as soon as cellular death happens.
You can very much relieve rigor. FLEX, ROTATE, MASSAGE, BEND. It reverses it self at 72 hour point why because the body lets go of its intravascular resistance it is in the interstitial
Tissue spaces. That is a very basic explanation. Please do not think the body will break. The bones will just like if you break anyone's bones if you try hard enough. I hope you don't think I am being mean or anything. That is not my intent.

This is an anatomy question that has a chemistry background, and without understanding the chemistry behind it, there is no possible way for you to understand what is going on. Go online and look up the chemical processes of how muscles flex! The ATP is no longer being supplied, no energy no moving.

Could you please answer this question for me? Once a person dies and rigor mortis is 4+,
How long has that person been dead?

The livor motis is (2 - 3+.
Thank You for yopur time.
Colleen