Postmortem changes begin occurring in animals immediately after death. The rate of these changes is affected by environmental temperature, the size of the animal, external insulation, and the animal's nutritional state and species. Key postmortem changes include autolysis by cellular enzymes, putrefaction by bacterial enzymes, rigor mortis, postmortem blood clotting, tissue staining by hemoglobin, hypostatic congestion, pseudomelanosis, imbibition of bile, postmortem emphysema, and rupture and displacement of organs. Differentiating postmortem from ante-mortem organ displacement relies on the presence or absence of passive hyperemia.

1. POSTMORTEM CHANGES
Dr. Jeny K John
Asst. Professor (Clinical Pathology)
Sardar Vallabhbhai Patel University of Agriculture and technology,
Meerut

2. Introduction
• As soon as animals dies certain changes occurs which are known as
postmortem changes
Factors affects the rapidity of their onset
1. Environmental temperature
Increased temperature increases the rate of enzymatic and bacterial
activity, animal decomposes rapidly
Refrigeration can be used for preservation

3. 2.Size of the animal
Larger the animal, more rapid the PM changes
Larger animals require a longer period of time before the body heat is
dissipated
3.External insulation
Thick cutaneous covering of fur, feathers, hair or wool prevent heat
dissipation
Sheep decomposes rapid

4. 4.Nutritional state of the animal
Fat is an insulating substance
Fatty animal decompose rapid (slower will be the loss of heat)
5.Species of animal
Species of animal determines the character of flesh
Pig flesh is soft, moist and contains fat, so decomposes fast
Horse flesh is dry and firm, decomposition is relatively slow

5. Postmortem changes includes
1. Autolysis
Digestion of tissues by their own cellular enzymes
When tissue is fixed or embalmed, cellular enzymes are inactivated by
formalin or alcohol and autolysis is prevented
2. Putrefaction
Decomposition of tissues by enzymes of saprophytic bacteria.
After death, bacteria from the digestive tract and body surfaces
invade, multiply and eventually digest the tissue with their enzymes

6. 3. Rigor mortis
• Shortening and contraction of muscles that occur after death and result
in stiffness and immobilization of the body
• Begins in the anterior portion and progresses in a posterior direction
(head, neck, trunk and limbs).
• Usually appears 1 to 8 hours after death
• Appearance is quickened by high external temperature, violent
exercise, or violent muscular contraction
• Retarded by low temperature
Emaciated animals: appears slowly, it is never very pronounced and
may not appear at all

7. 3. Rigor mortis
It disappears in the same order it appeared (head, neck, trunk and
limbs)
Muscular immobility usually disappears 20-30 hours after death
The rapidity with which it appears and disappears is used to estimate
the length of time the animal has been dead
Great importance in medico legal cases

8. 4. Postmortem clotting of blood
Coagulation of blood in vessels after death
In dead animals, the endothelial cells begin to degenerate and liberate
thromboplastin which then clots the blood within the heart, arteries
and veins
Anthrax: fibrinolysin produced by the bacteria liquefies the fibrin- no
clotting
Sweet clover poisoning: prothrombin activity inhibited- no clotting

9. 5. Imbibition with hemoglobin
Staining of tissue with haemoglobin
After death, the erythrocytes are hemolyzed by the cellular and
bacterial enzymes, and Hb is liberated.
Being soluble in body fluid, it diffuses into the surrounding tissues
and stains them red
6. Hypostatic congestion
Accumulation of blood in the ventral portion of organs and the entire
carcass due to the influence of gravity

10. 7. Pseudomelanosis
Appearance of grey, green, or black pigment in the tissues after death
Hydrogen sulphide produced during putrefaction combines with the
iron to form iron sulphide, a black pigment
Its concentration and combination with other tissue pigments result in
a variety of shades of green, grey and black
8. Imbibition of bile
Yellowish pigmentation of tissues occurring near the gallbladder
when bile pigments diffuse into the surrounding tissue
9. Postmortem emphysema
Accumulation of gas in tissues as the result of bacterial fermentation

11. 10. Rupture of organs and tissues
It occurs when gases produced cause progressive distension of body
structures until they burst
Usually occurs in stomach, intestine, diaphragm and ventral
abdominal wall
11. Displacement of organs
It occurs when the dead animal is moved or rolled, Intestine is usually
displaced
How to differentiate from ante-mortem malposition?
Displaced intestine (post mortem) will show no passive hyperemia
while the displacements occurring during life will show acute local
passive hyperemia.