بسم الله الرحمن الرحيم

Death and postmortem changes

Objectives 1- To know the early post mortem changes and their medicolgal importance post mortem( cooling,primary ,secondary flaccidity and reigor mortis). 2-To know the putrefaction process and its medicolegal importance. 3- To know the conditions that may replace putrefaction.

Postmortem changes These are the changes that occur after death as a result of cessation of vital functions. These changes include:- 1- PM cooling 2-PM lividity 3-PM rigidity 4-PM flaccidity 5- Putrefaction

Postmortem Cooling Definition:- It is the postmortem decrease in the body temperature due to stoppage of heat production while heat loss continues. Mechanism :- 1-Heat production stop due to stoppage of metabolism. 2- Heat loss continues due to radiation through air and conduction through contact surface

The body loses : 1.5 °F/hour in 1st 6-8 hours 1°F/hour till reaching the atmospheric temperature from 12-18 hours. Cadaveric temperature is measured: High up in the rectum by special thermometer. From liver and brain by microwave thermography. From skin temperature by infra red monitor.

Factors affecting Postmortem Coolness Atmospheric temperature. Air movements and humidity. (3) Relation between surface area of skin and body weight. (4) In fatty bodies. (5) Body temperature at the moment of death. (ie) death slow rate of heat loss in convulsion, heat stroke or acute infection ,and rapid heat loss in hemorrhage ,shock or wasting disease.

The rate of cooling:- -,5-1 C /hour in summer The rate of cooling:- -,5-1 C /hour in summer. -1- 1,5 C/hour in winter -2—3C /hour in running water. -Naked bodies lose heat more rapid than covered

Medicolegal Importance of Postmortem Cooling 1- Rough estimation the time of death. 2- Differentiation between the primary flaccidity and secondary flaccidity (in which the body more cold). 3- It gives an idea about the cause of death.

2-Postmortem Hypostasis (Postmortem lividity) Definition:- It is bluish or violet discoloration of the skin of the most dependent parts of the body, except the pressure points, after death.

Mechanism It is caused by gravitation and settling of the blood into the lax capillaries of the skin(due to loss of vascular tone). The red blood cells are most affected. Hypostasis is absent at pressure points due to mechanical compression of the vascular channels commonly, in the shoulders, against supporting surface(contact flattening).

Sequence of events: Gravitation of blood (after cessation of circulation) occurs immediately after death. Visible hypostasis (after filling of veins and capillaries) after 2 hours. Progressive expansion and gravitation of blood after 6- 8 hours reach the maximum intensity of the color and distribution

Medicolegal Importance 1- It is one of the sure sign of death. 2- Helpful in estimation of the time pass since death. 3- Detection of the position of the body at the time of death ,and if the body position has been changed after death.

4-It can give idea about the cause of death: Hanging. Co poisoning  Cherry – Pink Cyanide poisoning  deep blue – pink Asphyxia  Dark blue Hemorrhage  ill-defined or absent Methaemoglobinaemia  Brownish. Differential diagnosis: Hypostasis must be differentiated from contusions.

3-Postmortem rigidity (Rigor mortis) 3 Definition: It is a progressive hardening (rigidity) of all muscles of the body (voluntary and involuntary) gradually replacing the state of primary flaccidity.

Mechanism Physicochemical changes in muscle fibers. ATP depletion + lactic acid byproducts accumulation inside the muscle  acidity  irreversible shortening of the muscle due to formation of the contractile substance (actomyosin), which is shorter than uncombined actin and myosin, that causes muscle rigidity.

Sequence of events: The process becomes manifest after about 2 hours starting in the face then spread downwards. It becomes complete after 12 hours. Disappear gradually in the same sequence. Replaced by secondary flaccidity (autolysis) after about 24 hours.

Factors affecting rigor mortis: 1 Factors affecting rigor mortis: 1. Temperature(more rapid in hot weather). 2. Age and muscular development(slow in athletes due to increase ATP). 3.Cause of death(eg: In electrocution  rigor mortis is more rapid).

Rigor mortis in other tissues: Iris  unequal pupils. Heart  ventricular contraction. Dartos muscle of scrotum  compress testis, epididyms and seminal vesicle  postmortem extrusion of semen. Erector pili muscle  attached to hair  goose - flesh.

Medicolegal importance 1. Sure sign of death. 2. Estimation of time passed since death. If the body feels warm + flaccid  death < 3 hours. If the body feels warm + stiff  death 3-8 hours.

If the body feels cold + stiff  death 8-36 hours. If the body feels cold + flaccid  death > 36 hours. 3. May help in determination of the causes of death (very rapid in cases of death proceeded by convulsions due to depletion of the ATP) 4. Rigor mortis fixes the position of the body after death as it affects the agonists and antagonists at the same time.

Differential diagnosis of rigor mortis : (1) Cold stiffness: If atmospheric temperature (below zero)  hardening of tissues due to freezing of body fluid to solid and solidification of subcutaneous fat. On warming, the frozen body loses its rigidity and becomes flaccid. It is followed by rigor mortis.

(2) Heat stiffness: It is due to denaturation and coagulation of tissue proteins. Marked shortening (due to bulky flexors)  PM Boxer attitude of burned body. It does not followed by rigor mortis.

(3) Cadaveric spasm: It is a state of severe contracture of a group of voluntary muscles (usually hands). The whole body except this group of voluntary muscles will be in a state of primary flaccidity. It continues until rigor mortis sets in.

Causes: Suicidal: In cut throat or firearm injuries. Accidental: In drowning. Homicidal: Victim's hand firmly grasping hair, clothes or skin of assailant.

Differentiation between rigor mortis & cadaveric spasm Circumstances Severe nervous stimulation Physicochemical Nature of the process Death preceded by extreme nervous stimulation No special circumstances Circumstances of death nature Only a group of voluntary muscle All types of muscles Types of affected muscle

At the moment of death After 2 hours of death Start of appearance Extreme nervous stress before death 1ry flaccidity Preceded by Rigor mortis 2ry flaccidity Followed by

4- Postmortem Flaccidity Phases of muscle state after death:- 1- Primary flaccidity :-is a state of complete flaccidity of the body muscles immediately after death due to loss of muscle tone(within 2-3 hours) but the muscle respond to stimuli. 2-Rigor mortis.

3- Secondary flaccidity:- is a state of complete flaccidity of the body muscles occurs 18-25 hours after death ,and follows rigor mortis due to autolysis of the proteins but the muscles not respond to stimuli.

5- Postmortem decomposition (Putrefaction) Definition: It is the process of disintegration of soft tissues of the body leaving nothing but bones. OR: It is complete digestion of tissues by proteolytic bacterial activity and fermentation with the production of large amounts of foul smelling gases and liquids leaving nothing but bone (Skeletonization).

Mechanism It follows the arrest of the biochemical process which preserve the integrity of the cellular and subcellular membranes and organelles. 1- Autolysis:- The tissue component break up, hydrolytic enzymes are released from the intracellular lysosomal sacs.

I- Autolysis: Defintion: It is the process of self-dissolution by breaking down of complex protein and carbohydrate molecules of the body into simpler chemical forms. Caused by :- The action of digestive enzymes released from disintegrated cells. Site:-occur in organs rich in enzymes such as: pancreas, gastric mucosa and the liver.

2- Bacterial action:- Definition:- Putrefactive anaerobic organisms in GIT spread allover the body via blood vessels and thrive on the unprotected organic Components of the body. Bacterial growth – warmth, moisture are conditions favorable. Caused by:- Clostridium welchii, streptococci, E coli, B proteus.

The two parallel processes of decomposition have been distinguished: Mechanism of skin changes in putrefaction: The mal-odorous gases resulting from putrefaction as H2S, SO2, Co, CO2, NH3 are released within blood vessels causing their distension and greenish-black discoloration of the skin.

Sequence of events in Putrefaction: 1. After one day in summer and two days in winter: Greenish discoloration of the skin in right iliac region and cutaneous blood vessels in this area (sulph-haemoglobin). 2. After 4 days in summer and one week in winter): The greenish discoloration (Marbling phenomena) (arborization = distinctly visible dilated cutaneous blood vessels) spread all over the face and body.

Face is swollen, also abdomen and scrotum are distended. Dark coarse froth with bad smell is seen at the mouth and nostrils with protrusion of eye globe and tongue. Expulsion of the contents of large intestine and gravid uterus. The gases accumulate under the skin  putrefactive bullae.

3. After one week in summer and 2 weeks in winter. A- Tissue liquefaction: The abdomen bursts and the viscera  dark greenish doughy material with putrid odor. The most resistant organ to putrefaction is the prostate, which may survive for many months. The skin becomes dark green to black with peeling of epidermis (from ruptured bullae) and falling of hairs and nails.

B-Eggs of the flies hatch and larvae formed 4- after 6 months : Soft tissues disappear leaving bones and ligaments. 5- after 1 year:- Only bony skeleton remains ,as the time passes bones become lighter ,whiter and more brittle.

APPEARANCE OF MAGGOTS Flies lay eggs over the decomposed body- nose, mouth, vagina and anus in 18-36 hrs. After 24-36 hrs eggs hatch into larvae or maggots, enter the body and destroy the tissues. After 4-5 days develop into pupae. After 7-8 days into adult fly.

Factors affecting the rate of putrefaction 1. Age. 2. Temperature. 3. Air. 4. Humidity. 5. Presence of commensal bacteria. 6. The amount of blood in the tissues 7- The amount of subcutaneous fat. 8. Cause of death: Poisoning (e.g. arsenic, mercury). Infectious diseases with septicemia or pyemia. Elephantiasis and congestive heart failure. Non-bacterial gastroenteritis.

Conditions replacing putrefaction a)Adipocere:- in case of submersion in water. b)Mummification:-in case of death in desert. c)Maceration:- in case of death intrauterine.

a)Adipocere formation (saponification) Definition: It is the process of transformation of subcutaneous fat into a yellow solid waxy rancid smelly substances in bodies left under water with low atmospheric temperature for weeks.

The changes become visible after at least three weeks especially in fatty areas (cheeks, breasts, abdominal wall and buttocks) and is completed in about six months. Mechanism: Hydrolysis and hydrogenation of unsaturated fatty acids as palmitic and oleic into saturated fatty acids as stearic.

Medicolegal Importance Identification of unknown person due to preservation of the facial features. The cause of death may be preserved. It denotes long submersion under water. Time passed since death(3 weeks-6 months).

b)Mummificaiton Definition: It is the process of natural preservation of a dead body in hot dry climates with moving air currents and in sandy soil such as desert.

Mechanism: Progressive evaporation of body fluids +high atmospheric temperature  shrinkage and dryness of tissues and arrest putrefaction  preservation of the body and prevention of growth of organism. It starts to occur after 3 weeks from death and completed in one year.

Medicolegal importance: Estimation of time passed since death by the extent of dryness and shrinkage of the tissues. Identification of the person.

Maceration Definition: It is the process of aseptic autolysis of the fetus in utero after its death inside the membranes. It is aseptic condition that arrests putrefaction.

Characters: Flaccidity of the body. Brown red discoloration of the skin. Overlapping of skull bones. Importance: Intrauterine fetal death for several days.

Estimation of the time passed since death Means of estimation:- 1- Rate of cooling. 2- Extent of hypostasis. 3- Muscle state: primary flaccidity ,rigor mortis and secondary flaccidity. 4- Extent of putrefaction and other replacing conditions

5- Fauna of the cadaver (blue flies):lies eggs in orifices ,after 5 days they give larvae ,after 2 weeks they give pupa and after 3 weeks they give mature flies. 6- Rate of digestion and emptying the stomach. 7- Eye changes: intraocular pressure drops 12mmGg at time of death and becomes zero at 2-3 hours after death.

Medicolegal importance 1- In criminal cases:- Roughly estimate it was a murder. Eliminate or suggest suspects. Confirm or disprove an alibi. 2- In civil cases: Who inherits a property. Whether insurance policy was forced.

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