Does anyone know a lot about Rigor Mortis?

[clop]

We had a pet rat who was ailing for ages. She was ok(ish) at 9pm last night, but was found dead this morning before 7am.
We are just burying her (6pm) and rigor mortis still hasn't set in. I can't figure out why not. Could this shed light on what her cause of death or general condition was when she died?

Could it have been and gone? I believe that rigor mortis sets in and then leaves again?
In humans I think it starts to reduce after 12 hours (though Im not a pathologist). Maybe the process is quicker in a smaller animal?

AFAIK rigor sets in about 12hrs after death, but it wears off at some point. That's with people. No idea at all about rats. You could always ask the vet to do a pm.

what is rigor mortis?

i mean, i know it's the body going hard, but what is the physiological process which causes that hardening?!?!

link here

In people, it wears off after about 3 days. IME, its only a day in dogs. So if its anything to do with size or evolution, its probably less than a day in a rat!

Btw, I know nothing, but I assume its something to do with chemical reactions in your muscles, as its the muscles that harden, causing it.

Rigor Mortis happens when calcium ions diffuse across somewhere, causing permanent muscle spasms, due to abscence of oxygen because breathing has stopped -- is the best I understand RM.
RM is supposed to set in 1-12 hours after death, and typically lasts for 72 hours, typically peaking 12-24 hours after death.
At least, that's what I think I understand.
I wondered if the animal was suffering from a calcium deficiency; she had been eating very little; she was too weak to do anything.

I shudder to think what a PostMortem on a rat would cost!!

I don't need to know, she had a Good Innings and I'm satisfied that we looked after her properly, it's just an interesting puzzle.

DH is desperately trying to remember his 1st year undergrad medical stuff ---

all to do with the lack of oxygen in the muscles, the fibres harden as they are no longer undergoing chemical reactions which make them metabolise things .... or something? He says it was a long time ago!

Probably has worn off by now though.

Not much help at all I suppose but it will do till someone who knows what they are talking about comes along!

thanks bigstripey, I love that 'deathonline' is now in my history

Ok rigor mortis is actually very little to do with oxygen. For muscles to tense you need energy (ATP molecules are energy molecules) and you need calcium. The calcium means that muscle contraction is possible so the muscles go ahead and contract. The energy molecules mean that the muscle can stop contracting (the energy doesnt actually make the muscles contract). When the body dies,theres no energy so if the muscles and tensed up, or contracted, they cant stop, because theres no energy. Therefore,the muscles remain tensed.