Physiological reactions in the tissues of a dead body
Within a relatively short period of time after the death of a corpse, certain physiological processes (these are the so-called suprital reactions) are characteristic of a living organism: hair and nails grow, the viability of certain tissues and organs, blood cells and bone marrow, spermatozoa and so on
Physiological responses of dead body tissues have a completely natural tendency to gradually fade, which allows them to be used for forensic purposes to determine the duration of death.
During the first one and a half day pupils retain the ability to narrow after inserting into the anterior chamber of the eye 1% solution of pilocarpine and expand after injection of atropine. Within 5 hours after death, pupil contraction occurs 3-5 s after pilocarpine administration, in the period from 6 to 14 hours - after 6-15 seconds, from 15 to 24 hours - after 20-30 seconds, from 25 to 36 hours - in 1-2 minutes.
With a sharp blow to the biceps muscle of the shoulder, a local solid tumor appears as a narrow solid object, reflecting the continuing ability of the muscle to respond to mechanical irritation. In the first 2 hours after death, a high tumor forms, which quickly manifests itself and quickly disappears. In the next 2-4 hours it becomes flat, later emerges and later disappears. In the period from 6 to 8 hours after the death of the external reaction, there is no muscle to strike, only to the touch at the site of impact can be found its local compaction.
During the first 6-12 hours, the muscle reacts to the action of an electric current. The threshold of electrical excitability gradually increases: an hour after death, it is 0.1-1 mA, after 2 hours it increases to 2 mA, and after 6 hours reaches 40-50 mA.
The degree of electrical excitability of muscles can be determined by their reaction to the action of alternating and direct current. Electrodes are injected either into the circular muscle of the eye at the outer corners of the eye gap, or into the circular muscle of the mouth at its corners. The reaction is evaluated on a three-point system: 3 points - a reduction in the entire musculature of the face with a sharp contraction of the eyelids and the mouth observed within the first 2.5 hours after death; 2 points - compression of the eyelids or mouth only, if there is no contraction of the entire musculature of the face from 2.5 to 5 hours; 1 point - a slight twitching of the eyelids or muscles of the mouth from 5 to 12 hours. The ability to respond to the chemical effect is preserved by the sweat glands.
After the death of a person in a dead body, physical and chemical processes, called cadaveric phenomena, are not characteristic of the living organism. Distinguish between early and late cadaveric phenomena. The early develop within the first 24 hours after the onset of death, the later in the following days, weeks, months and years.
To early cadaveric phenomena include cadaveric stains, cadaveric (muscle) rigor, cooling of the corpse, drying and autolysis; to late - rotting, mummification, fattening and peat tanning.
Early Cadaveric Phenomena
Cadaver spots. After blood circulation ceases, blood under the influence of gravity begins to passively pass through the vessels to the lower body parts. After 1.5-2 hours, these amounts of blood accumulate in these departments, so that the skin in these areas acquires a blue-violet color. This phenomenon is called cadaveric spots. Lifetime unilateral (almost total) blood transfer is impossible, so cadaveric blemishes are considered an absolute sign of death.
The color of cadaveric spots throughout their area is relatively uniform. However, in some cases, with an increase in the permeability of the vascular walls, a sharp overflow of the venous network and a rapid rate of development of cadaveric blemishes, separate post mortal hemorrhages form cadaveric ecchymosis. They have a round shape and diameter is not more than 0.5 cm.
Three stages are distinguished in the development of cadaveric spots.
The first stage - hypostasis. It is characterized only by the movement of blood through the vessels. The relationship between the liquid and solid parts of the blood is preserved. Pressure on the cadaveric spot first leads to its disappearance, and then to a rapid recovery. If the corpse is turned over, the corpse stains will move to the new lower body parts. Hypostasis lasts the first 8-10 hours.
The second stage - stasis. A gradual release of plasma (liquid part of the blood) into the circulatory space and thickening blood remaining in the vascular bed. Pressure on the cadaveric spot does not cause its complete disappearance, it only fades, and then slowly restores the original intensity of color. If you change the position of the corpse, the new lower body parts will move only part of the blood, and the other will retain the original localization. Stasis lasts an average of 8 to 24 hours.
Third stage - Imbibition (impregnation). In later periods (24-36 hours), erythrocytes are destroyed, hemoglobin is released outside the vascular bed and impregnated with tissues surrounding the circulatory space. Even at strong pressure on the cadaveric spot, the intensity of its color does not change. When the position of the dead body changes, cadaveric spots retain their localization.
At the time of appearance and the dynamics of the development of cadaveric spots affect many factors. High ambient temperature speeds up their formation, low - slows down. The rapid rate of death, in which venous plethora is observed and the liquid blood state is maintained, is characterized by an earlier and more intense appearance of cadaveric spots. With agonal death, accompanied by intravascular formation of blood convolutions, cadaveric blemishes appear later, the intensity of their coloration grows slowly.
There is a dependence of the time of onset and intensity of coloring of cadaveric spots on the cause of death. When poisoning with blood poison, leading to intravital destruction of red blood cells, the onset of the final stage of development of cadaveric stains - imbibition - is accelerated. The rapid appearance of intense cadaveric spots is characteristic of pathological conditions characterized by intravital blood accumulation in the venous bed (for example, in most kinds of mechanical asphyxia). At the same time, when death from acute and massive blood loss, cadaveric spots can either be completely invisible or have a pale bluish-violet color.
The condition of cadaveric spots allows you to set the prescription of the onset of death. However, one should take into account the whole set of factors that can affect the time of their onset and the nature of development: the conditions of the environment, the rate of death and its cause, the volume of blood loss, etc. The gradual dynamics of development of cadaveric spots are used to judge the duration of death. To standardize the conditions for examining cadaveric stains, dynamometers are used to provide pressure and pressure on the cadaveric stain, as well as devices capable of objectively detecting the degree of decrease in the intensity of staining of the stain spot after pressure on it and the moment of complete restoration of the color after the pressure ceases. It should be noted that the time of death is determined not so much by the stage of development of the cadaveric spot as by the time necessary to restore its original color after pressing the dynamometer.
The obtained data are summarized in special diagnostic tables, graphs, nomograms, allowing to establish the prescription of death when inspecting the corpse at the scene.
The color of cadaveric spots often indirectly indicates the cause of death. For example, carboxyhemoglobin, formed in the blood during carbon monoxide poisoning, gives them a bright red color. When poisoning with methhemoglobin-releasing poisons, cadaveric blemishes acquire a grayish shade, and when poisoning with hydrocyanic acid and its salts, a cherry blossom. If death occurred at a low ambient temperature and the corpse was in such conditions for a long time, then the cadaveric spots have a pink color.
When comparing the posture of a corpse at the time of its detection with the localization of cadaveric spots, in some cases it is possible to establish the fact of the posthumous change in the position of the body and approximately - the time when this occurred. So, if the cadaveric spots are only in the upper parts of the body (for example, on the abdomen while the corpse is on the back), then its original position was violated in the stage of imbibition, i.e. 24-36 hours after death. The presence of cadaver spots on opposite parts of the body indicates a change in the position of the corpse in the stage of stasis, i.e. in the period from 8 to 24 hours after death. In the stage of hypostasis, cadaveric stains will completely move to the new lower body parts, and it will be impossible to establish the fact of the change in the position of the corpse, being guided only by their localization.
In areas of close fitting clothing (elastic pants, socks, bra, shirt collar, etc.), cadaveric stains are not formed. If the corpse is stripped in the stage of the imbibition, then in the area of the cadaveric spots, light stripes of pale skin will be visible from the clothing pressure. The latter will not arise if a naked body is put on tight clothing at the same stage. These signs are used to judge the fact of manipulation with a dead body.
Blood moves after death and in internal organs. Therefore, the parts of the organ, located above, usually pale, underlying, have an intense blue-red hue. Outwardly from hemorrhages, they are distinguished only by the diffuse nature of impregnation. Often, the truth is helped by special histological studies.Stump (muscle) rigor. Immediately after death, muscles relax, passive movements in all joints are possible in full. After 1-3 hours, the muscles contract and become denser: it is very difficult to open the mouth, bend or unbend the limbs of the deceased in the joints.
The rigor mortis covers the musculature of the internal organs. The stiffness of the heart muscle is well marked. During the life of such a consolidation of the muscle tissue does not occur, so the rigor mortis is the absolute sign of death.
Although rigor mortis begins simultaneously in all muscle tissue, its external manifestations in different muscle groups are expressed in different ways. Stiffness earlier becomes noticeable in short, broad and powerful muscles: chewing muscles, limb muscles.Stiffness, beginning 1-3 hours after death, increases and reaches its maximum development by the end of the first day. If it is arbitrarily violated, it is not restored.
Corpuscle rigor observed for several days. After 3-7 days under the influence of putrefactive processes, it gradually disappears.
The development of rigor mortis can be influenced by various environmental factors and the properties of the organism of the deceased. High temperature and low relative humidity accelerate the development of rigor mortis, low temperature and high humidity slow it down. The appearance of the postmortem, expressed in a slight degree of compaction of muscles, is delayed in children, elderly and physically weakened people. If the deceased immediately before his death performed heavy physical work, rigor begins earlier and turns out to be largely expressed. The same character of rigor is observed in death from acute and massive (profuse) blood loss. Death for some types of poisoning (phosphorus, pale toadstool) is accompanied by mild rigor mortis. At the same time, when death occurs during an epileptic fit or when poisoning with convulsive poisons (for example, strychnine), rigor mortis develops faster, more pronounced and lasts longer. With lesions of the medulla oblongata, rigor mortis can occur instantaneously and even fix the posture in which the person was directly before death (cataleptic rigor).
Cooling the corpse. Termination of the processes of exchange and heat generation in a dead body results in its cooling under the influence of a lower ambient temperature. Faster cool open parts of the body. A longer time retains heat in the rectum and internal organs.
Cooling the body occurs to a level that is below the ambient temperature by about one degree, which is due to the evaporation of moisture from the surface of the skin. It was found that at an ambient temperature of 15-16 ° C, the corpse temperature drops by an average of one degree every hour. The speed of cooling is influenced by the presence and nature of clothes, age (the corpse of a newborn is cooling down particularly quickly), infectious diseases, in which death occurs at the time of the greatest rise in body temperature, damage accompanied by blood loss, human exhaustion, etc. The nature of the environment (air, water, etc.) and its conditions (temperature, humidity, wind speed) or the degree of ventilation of the room, the presence of the body's contact with cooled massive objects. The temperature in the armpits varies and depends on the position of the upper limbs of the corpse. At present, the probe electrothermometry method is widely used to measure body temperature in the oral cavity, esophagus, rectum, in the tissues of some internal organs (for example, the liver). According to some data, the temperature in the liver of the corpse is approaching the ambient temperature by the end of the second day; the cooling of the corpse does not depend on the age, as well as the concentration of alcohol; clothing has a heat-saving function and provides a slower cooling of the body.
Cereal drying. After death, the physiological balance between loss and replenishment of the body with liquid is broken, a one-sided process of fluid loss occurs, which leads to the development of cadaveric drying. First of all, those parts of the body surface that during their lifetime were most moistened lose their moisture: mucous membranes, wound surfaces (for example, abrasions obtained shortly before death), etc.
Drying begins immediately after death, but its signs become noticeable only after a few hours (at room temperature after 2-3 hours): the red border of the lips loses moisture, elasticity and acquires a brownish color. If after the death of the eye the corpse remains half-open, then the open areas of the eyeball dry out. In this case, the cornea loses its luster, and on both sides of it (in the corners of the eyes) appear gray spots of a triangular shape (Lärše spots). The surface of posthumous damage to the epidermis after a while becomes dense and yellowish (parchment spots). Always wipe the edges of wounds, the surface of lifetime abrasions and burns. The dead bodies of newborns dry out especially rapidly, which can lose up to 100 g of body weight during the day with the evaporating moisture.
There is no method of objective registration of the degree of drying. Therefore, forensic medical examination is limited only by indicating the fact of cadaveric drying, and the degree of its severity is not used to judge the time of death.
Cereal autolysis (self-digestion). The disorganized enzymes of the body after the onset of death continue to affect the surrounding structures, destroying them. Macroscopic manifestations of autolysis are expressed in the softening and dilution of tissues. At a microscopic examination, the walls of the blood vessels are stratified, the mucous membranes are clotted, the cells swelling and dying. There are opacity of the cornea, the disintegration of red blood cells, melting of the pancreas and adrenal glands, self-digestion of the walls of the stomach, esophagus.
These changes are influenced by environmental conditions (temperature and humidity), the properties of the organism (age, some physiological conditions of women, the degree of development of the subcutaneous fat base and hydration of tissues), features of the process of dying (causes of death, rate of dying, etc.) . When external examination of the corpse at the scene of the accident, the forensic medical significance of autolysis is small, since its main manifestations are found only at the autopsy.
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