Effect of extreme temperatures Essay
The temperature of a person’s body, if one neglects small fluctuations of it at different times of the day, is a constant (about 37 °). Constancy of body temperature is provided by the mechanism of thermoregulation, which maintains a balance between two continuously occurring in the body opposite processes: heat generation and heat transfer. Heat formation – is a biochemical process, the result of metabolism in the body. Heat transfer – is a physical process, consisting in the transfer of heat from the body to the environment. Heat transfer is carried out by radiation of heat, heating of ambient air and objects, evaporation of sweat, loss of heat with body secretions.
The amount of heat produced in the body and lost depends on the temperature of the environment, the quantity and quality of clothing, the nature of the activity performed. Thanks to the mechanism of thermoregulation, equality between heat generation and heat transfer is ensured, and consequently, the stability of body temperature.Effect of Extreme Temperatures Essay. However, prolonged stay in conditions of extreme (too high or too low) ambient temperature can lead to a disorder of thermoregulation and human death (the general effect of extreme temperatures). In addition, damage can occur from contact (local) action of high or low temperature.
The general effect of high temperature (general overheating). In conditions of high ambient temperature, heat transfer is difficult, and heat formation continues, which creates the prerequisites for a general overheating of the organism.
High humidity, absence of wind, dense clothing (all this hinders the evaporation of sweat and reduces heat emission), overheating, heavy physical work (increases heat formation).
Increased sweating leads to a loss of large amounts of fluid and salts by the body, as a result, the physicochemical properties of the blood change significantly and metabolism is disturbed.
The overall effect of high temperature largely depends on the individual characteristics of the organism. Other things being equal, overheating takes place more quickly by the pathology of the cardiovascular system, obesity and some other diseases. Especially prone to overheating, young children, because their thermoregulatory mechanisms are not perfect enough.
Clinically, the general overheating of the body usually manifests itself in the form of a heat stroke, accompanied by headache, nausea, fatigue, weakness, lethargy, drowsiness. In unadapted to heat people, thermal shock can develop at an ambient temperature above 45-47 ° C after 4-6 hours of exposure to the sun. With increasing air temperature, sweating and evaporation increase. At a temperature of more than 35 ° C a person loses about 5 liters of sweat per day, which corresponds to a yield of almost 3000 kcal.Effect of Extreme Temperatures Essay.
Gradually, clinical symptoms increase, there may be a short-term loss of consciousness, pulse and breathing become more frequent, sweating stops, body temperature rises to 41-42 °. Against this background, excitement, convulsions, a heavy unconscious state suddenly arise, involuntary discharge of feces, urine occurs. Death comes from paralysis of the respiratory center.
A similar clinical picture can be observed with a so-called sunstroke, which is a combination of overheating with the action of sunlight on the uncovered head.
When autopsies of people who died from heat or sunstroke, there are no specific signs. Detecting the fullness of the internal organs, some blood thickening, small hemorrhages in the substance of the brain, on the surface of the heart and lungs, swelling of the lungs and brain.
Diagnosis of death from overheating is based on taking into account the circumstances of the onset of death, the clinical picture (if it is known) and on excluding other possible causes (trauma, poisoning, disease).
Local heat action. Burning effects are caused by flames, hot water and other liquids burning or heated to a high tar temperature (napalm, bitumen) and resinous substances, hot bodies. There are four degrees of burns: I – characterized by redness and swelling of the skin; II – the appearance on the skin of blisters filled with a transparent yellowish liquid; IIIa – necrosis of the surface layers of the skin; IIIb – necrosis of the skin to the full depth; IV – necrosis of the skin and underlying tissues (subcutaneous tissue, muscles, etc.).
Small burns of I-II degree heal, leaving no trace. After burns of III-IV degree, gross scars appear on the body.
Burns caused by various damaging factors have differences that allow to establish their origin. So, for burns, flames are characterized by the burning of the burn surface, hair loss, sometimes charring of tissues. Burns with a hot or boiling liquid with a large area of damage tend to predominate blisters, the lack of soot and hair loss. Effect of Extreme Temperatures Essay. Spreading under the clothes, the liquid causes burns in the form of elongated tongues. Sometimes on clothes there are traces of spilled liquid: coffee, milk, tea, soup, etc.
The severity of the burn injury depends not only on the degree of burn, but also on the area of the lesion, which is usually defined as a percentage of the surface of the whole body. It is estimated that the areas of the anterior and posterior surface of the trunk make up 18% of the total body area, the head area 9%, the upper limb 9%, the lower extremity 18%, the perineal 1%, the neck 1%.
Although burns are the result of a local action of high temperature, they are accompanied by changes in the whole organism, the aggregate of which is called burn disease. In the clinical course it is divided into four periods: burn shock in the first two days; 2nd – burn toxemia (intoxication), lasting from three to 10 days; 3rd – a burn infection, usually starting from the tenth day; 4th – burns exhaustion. Death can occur in any period of the burn disease, and depending on this, the predominant immediate causes of death will be either shock, or burn intoxication, or infectious complications, or burnout.
A special place in forensic medicine is the study of corpses found on the conflagration. The death of people in this case may be connected with a fire, but there may be cases of murder and subsequent arson of the premises to conceal the traces of the crime. If a person is in a burning room and has not managed to get out, he usually dies from carbon monoxide poisoning (carbon monoxide), then the dead body is exposed to heat, burning and charring. Clothes on the corpse burn, but part of it, located under it, is usually preserved. The skin acquires a brown color, linear tears appear on it, somewhat resembling cut wounds. In areas of tight clothing, burns may be absent. Under the influence of high temperature, muscles lose moisture and contract. As a result, regardless of whether a living or dead person has fallen into the fire, the corpse takes the pose of the boxer (his arms and legs are half-bent and pulled to the trunk). Effect of Extreme Temperatures Essay.
The local action of high temperature on the head of a corpse can cause blood to move in the cranial cavity, resulting in a significant hemorrhage between the skull and the dura mater (epidural hematoma). The further action of the flame first leads to charring and destruction of the skin, and then (depending on the duration of the action) and deeper layers – muscles, bones and internal organs. First of all, small parts of the body (fingers, hands, forearms, etc.) are small, the more massive parts last longer. Complete destruction of the corpse, as a rule, does not occur.
In some cases, there is a need to establish the identity of the deceased.
The following signs indicate the intravital effect of high temperature:
1. Light, raw and non-smoked narrow strips of skin, radially diverging from the outer and inner corners of the eyes, indicating a lifetime squint.
2. Presence of particles of soot in the inspiratory ways, in the oral cavity, esophagus, stomach. The soot in the airways proves that a person breathed in an atmosphere of fire, the soot in the esophagus and stomach indicates swallowing movements that are made after the start of the fire.
3. Burns of the mucous membrane of the respiratory tract (larynx, trachea, bronchi) that occur when breathing hot air.
4. The presence of carboxyhemoglobin in the blood at a concentration of more than 20%, which is the result of the inhalation of smoke containing carbon monoxide, i.e. indicates the fact of breathing. Effect of Extreme Temperatures Essay. In fires, postmortem penetration of carbon monoxide can occur through the skin, but then the formation of carboxyhemoglobin in the blood, as a rule, does not exceed 20%.
5. Detection of soot in the axilla of the base bone (the base bone forms the base of the skull).
6. The presence of a small amount of soot in the blood vessels of internal organs.
In practice, there are also attempts to burn the corpse to conceal the crime, and often the corpse is preliminarily dismembered. In domestic conditions it is almost impossible to completely cremate the corpse of an adult person (it takes 40-60 hours to burn it if it is doused with kerosene – 10-12 hours). The cremation of the baby takes 2-3 hours.
In a closed volume, incineration (cremation) is carried out in air heated to 860-1100 ° C, when the body burns to white dust-like ash and easily cleavable into ashes parts of bone tissue. The total mass of the corpse remains is 1.25-2.5 kg (depending on the initial weight of the cremated one). At 600 ° C (the burning temperature of the fire) and only charred, but retain their anatomical structure. (Complete destruction of body tissues before white ashing takes place at a temperature of 1000 ° C.)
Inspection of the scene allows you to identify many valuable data. So, in the ash of the stoves and on the site of the fire, charred bones can be found, on which it is possible to determine their species identity, age and gender of the victim. Spectral study of ash helps to establish the presence in it of precious metals, if products from them (dentures, rings, earrings, etc.) were exposed to the flame along with parts of the corpse.
Issues resolved by forensic expertise:
1. Was death the result of a general overheating of the body?
2. Was death due to burn injury or other causes?
3. What are the causes of burns: the action of a flame, hot liquid or hot gases?
4. A living person or a corpse was exposed to the action of a flame?
5. Are the lesions detected on the corpse (for example, fractures of the bones of the extremities, ribs, skull fractures, hemorrhages, etc.) the result of the action of high temperature or are they due to other causes? Effect of Extreme Temperatures Essay.
6. Are corpses that are not associated with heat? Are they lifelong or posthumous? What is their possible origin?
7. Could certain factors of the external environment or individual characteristics of the organism contribute to death from general overheating?
8. Are there thermal burns on the body, what are their localization, area and degree of injury? When are burns caused: in vivo or posthumously?
9. Do not the bone remains found in the hearth of the fire belong to a person?
10. Is it possible to establish the identity of a charred corpse if there is evidence of a likely victim? Effect of extreme temperatures Essay.