Transcript Introducing the Mortis Brothers

Objective: SWBAT use the evidence of livor mortis, rigor mortis, and algor mortis to
calculate the approximate time of death
Do Now:
Review Game

Purpose: Be able to guess your word(s) by
using only minimal clues
Round 1: charades (no talking)
 Round 2: one word
 Round 3: definition or example

Introducing the Mortis
Brothers
The Chemistry, Math and Biology
of Death
Rigor Mortis
Skeletal muscles partially contract
 Joints stiffen, lock in place
 Onset is 10 minutes to several hours
 Rapid cooling can delay it
 Lasts up to 72 hours
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Chemistry of Rigor Mortis
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Living muscle cells use oxygen to burn glycogen
After death no oxygen—anaerobic glycosis
makes lactic and pyruvic acids
pH falls as acidity increases
Acid promotes a reaction between actin and
myosin which work together to contract the
muscle
Muscle shortens until all ATP and acetylcholine is
used up
Exit Ticket
In 4-5 full, complete sentences
Give a definition of rigor mortis, livor mortis,
and algor mortis. How does this relate to
calculating the manner, cause, mechanism
or time of death.
BRING YOUR CALCULATORS FOR
THURSDAY!!!
Muscle Contraction
Ca and ATP Ratchet the Fibers
End of Rigor Mortis
The muscles relax when the body starts to
decompose and the fibers begin to break
down
 Intracellular digestive enzymes are
released from the lysosomes as the cells
begin to disintegrate, destroying the
muscle fibers (autolysis)
 Meat is more tender after rigor mortis has
passed (Aged Beef?)

Livor Mortis
Heart stops beating which had been
mixing blood
 Red blood cells are denser so they sink
 Maroon to blue color develops at lowest
points
 Visible 30 minutes-2 hours after death
 Tells you if the body was moved.
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Livor Mortis
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Soon after death, blood is still in vessels, so
pressure on an area pushes the bood out—
– get blanching up to approximately 4 hours after death
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As time goes on blood vessels break down as do
blood cells and hemoglobin break down pigment
moves out into the tissues
– No more blanching
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Pressure or constrictive clothing prevents blood
from pooling locally
– Contact pallor
Livor Mortis
Livor Mortis
After death cells release enzyme
(fibrinolysins) that prevents clotting
 Blood in body stays liquid after death
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– Permanently won’t clot 30-60 minutes after
death
Algor Mortis
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Body cools by
– Radiation
 (the higher the body temperature the more heat lost)
– Conduction depends on surface contact
 faster if in water because enhanced contact
– Convection
 Wind cools faster
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Rate of cooling of body after death
– 1.5 °F per hour under “normal conditions”
– No real conditions are “normal”
Algor Mortis
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Ambient temperature
– Newton’s Law of Cooling
T
 k (T (t )  Tambient (t ))
t
 T is body temperature, t is time
 The bigger the temperature difference, the faster
the cooling rate
 Outdoors, temperature varies a lot—must correct
formula by varying Tambient
Algor Mortis
If ambient temperature is constant,
Newton’s Law of Cooling is easy to solve
 Measure temperature at two different
times without moving the body to find k

T (t )  Tambient  (T0  Tambient )e
 kt
Algor Mortis
100
Body Temperature (F)
Ambient T
Body T
90
80
70
0
2
4
6
8
Time Since Death (hrs)
10
12
14
Algor Mortis
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Clothing
– Insulates body from heat loss
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Obesity
– Fat insulates, temperature falls more slowly
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Ratio of surface area to volume
– Children, thin people cool faster
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In water?
– Cooling is faster since water is a better
conductor of heat than air
Algor Mortis
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New issue
– Is there a plateau before body temperature
starts to fall after death?
– May be up to several hours
– Anaerobic cellular chemistry continues after
death
– Cellular chemistry releases energy as heat