Common Postmortem Changes

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  • 0:08 Common Postmortem Changes
  • 0:41 Pallor Mortis
  • 1:16 Algor Mortis
  • 2:51 Rigor Mortis
  • 4:02 Livor Mortis
  • 5:59 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will discuss four common postmortem changes. Namely, we'll look into algor mortis, rigor mortis, pallor mortis, and livor mortis. We'll talk about what they mean, why they occur, and how they might be used by a crime scene investigator.

Common Postmortem Changes

I'd like to introduce you to the mortifying Mortis Brothers.

image of four people

They are, from left to right, Pal, Al, Rig, and Liv Mortis. They are all involved in postmortem changes, or changes that occur to a body following death.

They are pretty disgusting and may cause some of you to be a bit queasy in certain parts of this lesson, but if you're a fan of CSI, then you'll definitely enjoy this lesson and its look into the four fundamental ways in which a body changes after a person's death.

Pallor Mortis

Our first brother is called Pal, or pallor mortis, which refers to the paleness of a person's skin associated with death. I think that's pretty easy to remember. This pallor, or paleness, happens very rapidly, within a minute or so, after death. That's because the heart stops pumping blood when a person dies.

Once the blood stops circulating, it begins to pool away from the edges of the skin towards the dependent regions of the body, resulting in whitening of the skin. This will be an important point to recall towards the end of this lesson.

Algor Mortis

Our second brother is Al, who is more technically known as algor mortis. No, by the way, he's not related to Al Gore, and he didn't invent the Internet. Algor mortis refers to the cooling of the body after death.

'Algor' refers to coldness, while 'mortis' refers to death. But an easier way I remember that algor mortis refers to the cooling of the body after death is that 'algor' sounds like 'Al Gore.' If you're a fan of Al Gore, then you'll remember it because Al Gore would want our planet to cool down a bit so we don't suffer from the nasty after-effects of global warming.

The reason the body begins to cool after death is because the energetic processes that occurred while someone is alive stop. It's akin to shutting down the coal plant that provides you with power. No coal means no electricity, which means no heat for your home.

The body will cool to the ambient, or surrounding, temperature of its environment. The rate of cooling will depend on many factors, such as:

  • The surrounding temperature
  • Body mass
  • The movement of air

and many other factors that must be taken into consideration by a crime scene investigator in order to help use this clue to establish a potential time of death, although often times the body is found too late to use algor mortis as a clue for establishing the time of death.

Rigor Mortis

Our next brother is Rig, or rigor mortis to be more precise. Rigor mortis refers to the contraction of muscles after death. That whole stiff dead man thing you've probably heard about - that's rigor mortis.

The stiffening of the muscles begins about 1-6 hours after death and lasts about a couple of days.

However, these time frames are all relative and are influenced by factors such as:

  • Medical conditions
  • Nutritional status
  • Environmental temperature
  • Muscular build

And so on. These are all things that forensics teams must take into consideration!

This contraction of musculature occurs as a result of the depletion of the body's energy currency, ATP. Once the muscles contract and the body's ATP and glycogen stores are depleted, the muscles cannot relax until the body begins to break down and decay.

The way to quickly remember what rigor mortis refers to is to simply pronounce the first word, 'rigor.' It clearly resembles via its first three letters the word 'rigidity.'

Livor Mortis

Finally, we get to meet Liv, or livor mortis. Livor mortis refers to the gravitational pooling of blood in the dependent portions of the body. Livor mortis is sometimes also called 'hypostatic congestion' among other names.

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