After the circulation of blood stops in the body of the deceased, blood and other body fluids, according to the laws of physics, move to the lower sections (under the influence of gravity). In this case, blood begins to flow from arterial vessels into venous and overfills them. It should be noted that the vascular walls are characterized by increased permeability. In this regard, blood begins to leak out of the vessels and accumulate in the tissues. As a result, early cadaveric changes begin. Leaked blood gives the skin an appropriate color. As a rule, cadaverous spots are dirty purple with a predominance of different shades. These shades depend on the cause of death and other factors.
So, for example, if death came from carbon monoxide poisoning, then the cadaverous spots are bright red. This is due to the fact that hemoglobin passes into carboxyhemoglobin. If poisoning by cyanide compounds occurred, then cadaveric spots will have a peculiar cherry hue. The corpses that were in the cold, they will be bright pink. This is due to the fact that hemoglobin is oxidized by atmospheric oxygen, which penetrates through microcracks of the skin. In turn, microcracks are formed due to freezing of fluids in the body.
If spots appeared on the body from behind, then this indicates that the corpse was on its back. If the deceased was located on the stomach, then, accordingly, they will arise on the front surface. If there was a hanging and the corpse was not removed for a long time from the loop, then the cadaveric spots are located mainly on the feet, legs, forearms.
Within twelve hours after death, the stage of hypostasis continues. The liquid component of the blood is located in the vessels. Blood, when pressed, leaves the vessels, and when the pressure ceases, it fills them again. This contributes to the disappearance of cadaveric spots and their movement when moving the body to the underlying departments.
After twelve hours, the stage of diffusion (stasis) begins. It lasts until twenty-four hours. In this case, cadaveric spots begin to fade, but do not completely disappear. This is due to the fact that, by stretching the vascular wall, the liquid part of the blood begins to penetrate into the tissues. At the same time, hemolysis of red blood cells begins. At this stage, when changing the position of the body, the movement of cadaveric spots does not occur, but their intensity decreases to some extent.
On the second day after death, the stage of imbibition begins. At this stage, a good fixation of cadaveric spots is noted, they do not move, do not fade when pressed. This is due to the fact that soft tissues are impregnated with blood.
The degree to which cadaveric spots are expressed depends on the nature of the pathology, the cause of death and the very mechanism of dying. In the case of death with prolonged agony, from acute blood loss, there is a weak severity. With rapid death, for example, from electrical injury, mechanical asphyxia and other things, the severity is much higher.
It must be said that the presence of cadaveric spots is the earliest sign of death. They show the position of the body immediately upon death and the likely changes in position after death. According to one or another features of cadaveric spots, you can determine the time when a person died.
After death, muscle relaxation occurs. They become supple and soft. Two or four hours later, signs of rigor mortis begin to appear. All muscles acquire firmness, become dense, contract to some extent, fixing the body posture (position). Significant effort is required to change the posture of the deceased.