4. Physical and chemical mechanisms of the resting potential occurrence Membrane potential (or resting potential) is the potential difference between the outer and inner surface of the membrane in a state of relative physiological rest. The resting potential occurs at

5. Physico-chemical mechanisms of the action potential occurrence

11. Mechanisms of occurrence of bone injuries under the action of blunt objects. Damage to the bones of the skull On the type of bones, the nature of the damaging object, on the strength and speed of the traumatic effect, as well as on the direction of the force in relation to the damaging

16. Mechanisms of occurrence of injuries when moving with a wheel (wheels) of motor transport As an independent type of car injury, crossing with a wheel (wheels) is rare, combined more often with a blow by a car. Up to 90% of all crossings are made by trucks.

19. Railway injury. Mechanisms of damage. Issues resolved by a forensic medical examination Railway injury refers to a rail injury. Varieties of rail injury have much in common with types of car injury. Formation mechanisms

25. Related factors of the shot. Types of gunshot wounds. Features of the inspection of the scene of the incident The accompanying (additional) factors of the shot are considered in addition to the action of the bullet itself.1. Mechanical action of powder gases and air from the barrel. Air

44. Early cadaveric changes. Origin mechanisms. Forensic medical significance Cooling of the body, cadaveric spots, rigor mortis, drying of tissues are early cadaveric phenomena. When cooling a corpse, usually during the first tens of minutes after

Factors and mechanisms of development of osteochondrosis of the spine As you already know, the spine consists of vertebrae, between which there are cartilage - discs and joints. The vertebrae are connected and surrounded by powerful muscles and ligaments. Balanced interaction of muscles, ligaments,

14.5. Shot and the mechanism of formation of gunshot injuries

A shot is a collection physical phenomena, accompanied by the ignition of a powder charge in the charging chamber of a firearm and the departure of a projectile from the bore. When the striker hits the primer, an explosion of the shock composition occurs. The resulting flame through the seed holes penetrates into the cavity of the sleeve and ignites the powder.
When the gunpowder is ignited, its explosive transformation occurs, accompanied by a huge increase in pressure in the bore, as a result of which the bullet receives a translational and rotary motion. Due to the pressure of the gases, the weapon recoils, the barrel of which is thrown up and somewhat to the left. In automatic weapons, gas pressure is used to eject the spent cartridge case and reload the weapon.
A firearm has a very high kinetic energy, which it transfers to tissues upon contact with them. The effect of a firearm on tissues depends on its weight (mass), flight speed and the physical condition of the tissues (their resistance). The kinetic energy of a moving projectile is defined as half the product of its mass times the square of its flight speed.
The bullet, in contact with the tissues, instantly causes their oscillation, which in the form of a shock wave propagates to neighboring tissue particles. Following the bullet, a significantly larger pulsating cavity is formed, which transmits oscillatory movements to neighboring tissues. Therefore, the action of a bullet is composed of impact (direct action) and the impact of energy transmitted to the sides (lateral action).
With a significant kinetic energy of the bullet at the moment of contact with the tissues, it acts as a punch, knocking out a piece of tissue (punching action). With a decrease in energy, the bullet only pushes the tissues apart, and their defect is not formed (wedge-shaped action), and when the bullet hits organs containing a liquid or semi-liquid medium, a hydrodynamic effect is observed, leading to rupture of the organ. With little energy (for example, at the end), the bullet acts like any blunt solid object (concussion action).
When fired from the bore, in addition to the bullet, flames, gases, soot and powders fly out. When firing from a lubricated weapon, droplets of weapon lubricant also fly out of the barrel bore. These particles that occur during shots are additional factors of a shot and leave certain traces on the human body, and sometimes even damage.
At the time of the shot, a flame appears at the muzzle of the weapon, the nature and magnitude of which depend primarily on the type of gunpowder. Black (smoky) powder produces a significant flame and many red-hot unburned powders, which can cause hair fall, skin burns, and even clothes on fire. The thermal effect of smokeless powder is much less pronounced and can lead to slight shedding of clothing lint or skin vellus hair.
Hot propellant gases have a bruising effect, causing the formation of parchment stains. The thermal effect of gases is insignificant. When fired at point-blank range or at close range, when a dense tissue (bone) is located under the skin, gases exfoliate it with muscles and periosteum, often forming significant gaps. The latter are the most important sign of the action of gases.
The soot formed as a result of the combustion of gunpowder extends to a distance of 20-30 cm from the muzzle of the weapon. The intensity and diameter of the injection will be different and more pronounced at a closer distance.
The shape of the inflate can be round when shot at a right angle to the surface of the body or oval if the barrel of the weapon at the time of the shot was located at an angle to the surface of the body.
When fired, there is no complete combustion of gunpowder, and therefore unburned or partially burnt powders at close distances can be found on an obstacle. They can penetrate into the fabric of clothing, pierce it, and also precipitate the epidermis. In some cases, they are found deep in the wound. Detection of powders in a circle entrance wound indicates the close range of the shot. In addition, the study of powders allows us to resolve the issue of the type of powder used.

Example.
Citizen K., aged 36, on December 17, 1998, shot from a pistol in the head.
Forensic diagnosis:
1. Gunshot single bullet penetrating wound of the head. The entrance hole in the chin area with the presence of stamp marks on the skin, soot and powders around the wound. Exit hole in the occipital region. Multiple small and large comminuted fractures of the bones of the base and calvaria. Extensive destruction of the substance of the brain with hemorrhages along the wound channel and the introduction of small bone fragments.
2. Spatters of blood on the back surface of the 1st, 2nd, 3rd fingers of the right hand.

A shot is a set of physical phenomena accompanied by the ignition of a powder charge in the charging chamber of a firearm and the departure of a projectile from the bore. When the striker hits the primer, an explosion of the shock composition occurs.

The resulting flame through the seed holes penetrates into the cavity of the sleeve and ignites the powder.

When the gunpowder is ignited, its explosive transformation occurs, accompanied by a huge increase in pressure in the bore, as a result of which the bullet receives translational and rotational motion. Due to the pressure of the gases, the weapon recoils, the barrel of which is thrown up and somewhat to the left. In automatic weapons, gas pressure is used to eject the spent cartridge case and reload the weapon.

A firearm has a very high kinetic energy, which it transfers to tissues upon contact with them. The effect of a firearm on tissues depends on its weight (mass), flight speed and the physical condition of the tissues (their resistance). The kinetic energy of a moving projectile is defined as half the product of its mass times the square of its flight speed.

The bullet, in contact with the tissues, instantly causes their oscillation, which in the form of a shock wave propagates to neighboring tissue particles. Following the bullet, a significantly larger pulsating cavity is formed, which transmits oscillatory movements to neighboring tissues. Therefore, the action of a bullet is composed of impact (direct action) and the impact of energy transmitted to the sides (lateral action).

With a significant kinetic energy of the bullet at the moment of contact with the tissues, it acts as a punch, knocking out a piece of tissue (punching action). With a decrease in energy, the bullet only pushes the tissues apart, and their defect is not formed (wedge-shaped action), and when the bullet hits organs containing a liquid or semi-liquid medium, a hydrodynamic effect is observed, leading to rupture of the organ. With little energy (for example, at the end), the bullet acts like any blunt solid object (concussion action).

When fired from the bore, in addition to the bullet, flames, gases, soot and powders fly out. When firing from a lubricated weapon, droplets of weapon lubricant also fly out of the barrel bore. These particles that occur during shots are additional factors of a shot and leave certain traces on the human body, and sometimes even damage.

At the time of the shot, a flame appears at the muzzle of the weapon, the nature and magnitude of which depend primarily on the type of gunpowder. Black (smoky) powder produces a significant flame and many red-hot unburned powders, which can cause hair fall, skin burns, and even clothes on fire. The thermal effect of smokeless powder is much less pronounced and can lead to slight shedding of clothing lint or skin vellus hair.

Hot propellant gases have a bruising effect, causing the formation of parchment stains. The thermal effect of gases is insignificant. When fired at point-blank range or at close range, when a dense tissue (bone) is located under the skin, gases exfoliate it with muscles and periosteum, often forming significant gaps. The latter are the most important sign of the action of gases.

The soot formed as a result of the combustion of gunpowder extends to a distance of 20-30 cm from the muzzle of the weapon. The intensity and diameter of the injection will be different and more pronounced at a closer distance.

The shape of the inflate can be round when shot at a right angle to the surface of the body or oval if the barrel of the weapon at the time of the shot was located at an angle to the surface of the body.

When fired, there is no complete combustion of gunpowder, and therefore unburned or partially burnt powders at close distances can be found on an obstacle. They can penetrate into the fabric of clothing, pierce it, and also precipitate the epidermis. In some cases, they are found deep in the wound. The detection of powders in the circumference of the entrance wound indicates the close distance of the shot. In addition, the study of powders allows us to resolve the issue of the type of powder used.

Forensic diagnosis:

1. Gunshot single bullet penetrating wound of the head. The entrance hole in the chin area with the presence of stamp marks on the skin, soot and powders around the wound. Exit hole in the occipital region. Multiple small and large comminuted fractures of the bones of the base and calvaria. Extensive destruction of the substance of the brain with hemorrhages along the wound channel and the introduction of small bone fragments.

2. Spatters of blood on the back surface of the 1st, 2nd, 3rd fingers of the right hand.

5160 0

In the mechanism of formation of a gunshot wound, four factors are of primary importance.

The first factor is the impact of the shock wave. At the moment of contact of the bullet with the surface of the affected tissues, a large pressure instantly arises at the point of contact, causing compression of the medium at the specified point. The compaction of the medium, called shock warfare, propagates ahead of the moving bullet at the speed of sound (1465 m/s in the tissues of the body) and overtakes the bullet, as the movement of the bullet in the tissues gradually slows down. In the tissues, as a result of the transfer of the kinetic energy of the injuring projectile, pressure (compression) waves arise in which two phases are distinguished. The first phase of the pressure wave constitutes the shock wave (Fig. 1). It is characterized by a steep positive pressure front (up to 1000 kPa) and a short duration (up to 0.5 µs). Due to the short duration of existence, it does not play a leading role in the formation of a gunshot wound. The second phase of pressure waves - low-frequency waves, which are characterized by a much longer duration, form the phenomenon of cavitation, constitute the third factor in the formation of a gunshot wound and play importance in the formation of a zone of secondary necrosis.

Rice. Fig. 1. Pulsed radiograph (A) of a block of 20% gelatin in the phase of maximum runway development (a - pressure transducer) and oscillogram (B) of a recording of the shock-wave process in 20% gelatin when a 7.62 mm bullet was fired at the block from an AKM assault rifle with speed 715 m/s. Following the "shock" wave (Pm=15-20 kPa) low-frequency pressure waves, with a duration of up to 20-30 ms.

The second factor is the impact of the injuring projectile. Basic ballistic performance wounding projectiles is their muzzle velocity. In accordance with this, low-speed (ν0< 400 м/с) и высокоскоростные (ν0 >760 m/s) wounding projectiles. The damaging effect increases with an increase in the angle of nutation of the bullet in the tissues and reaches a maximum when it is overturned or deformed. This is explained by an increase in the cross-sectional area of ​​the projectile entering the tissues, an increase in the drag coefficient and, as a result, an increase in the kinetic energy transferred to the tissues. When passing through the tissues of a conventional 7.62 caliber bullet in a stable position, 20% of the kinetic energy is transferred to the affected tissues, while passing a small-caliber tumbling bullet with initial speed flight 900 m/s - 60%. Thus, as a result of the impact of high-speed wounding projectiles, a qualitatively new type gunshot wounds (Fig. 2, 3).

Rice. 2. Impulse radiographs of the movement of bullets in blocks of 20% gelatin:

A - shot with a 7.62 mm bullet from an AK-47 assault rifle; B - shot with a 5.45 mm bullet from an AK-74 assault rifle

Rice. 3. Pulse radiograph.

Shot 5.56 bullet out automatic rifle MI16At (USA) in 20% gelatin block. Flattening and fragmentation of the core and shell of the bullet are visible. The deformed bullet leaves behind a significant wound channel.

Third factor (basic and gunshot wound specific) - side impact energy. In the process of passing a wounding projectile, which has a huge kinetic energy, through the tissues - in its wake, as a result of the cavitation effect (tissue vibrations), a temporary pulsating cavity (RWY) is formed. Depending on the energy transferred to the tissues by the wounding projectile, the diameter of the cavity exceeds the diameter of the wounding projectile by 10–25 times;

Rice. 4. Pulsed radiographs

Formation of a runway in a block of 20% gelatin (A) when a 5.45 mm bullet is fired from an AK-74 assault rifle at a speed of 900 m/s. After the subsidence of the temporary cavity (B), a cone-shaped channel remains - a permanent cavity (C), in the walls of which there are deep cracks and small tears of gelatin.

The formation of a temporary pulsating cavity occurs in accordance with the laws of hydrodynamics. The volume of the cavity is proportional to the energy of the injuring projectile transferred to the tissues, and is expressed by the dependence:

where W is the volume of the temporary pulsating cavity; ∇Е - kinetic energy transferred to tissues, α - coefficient of proportionality.

The volume of the temporary cavity is proportional to the initial kinetic energy of the injuring projectile, the deceleration coefficient, the cross-sectional area of ​​the injuring projectile, the length of the wound channel and tissue density.

It follows from the equations that small caliber bullets (5.45–5.56 mm) lose their kinetic energy in tissues at a shorter distance than larger caliber bullets (7.62 mm) due to the high drag coefficient. The largest runway dimensions are formed at the point of maximum deceleration of the injuring projectile, where the greatest release of kinetic energy occurs. Bullets of caliber 7.62 mm are distinguished by a stable position in flight, therefore their deceleration increases as they move through the tissues and, therefore, the dimensions of the runway are the largest at the exit hole of the wound channel, the deceleration coefficient increases in proportion to the increase in the angle of deflection of the bullet and reaches a maximum at an angle of 90 ° . For high-velocity tumbling bullets with a displaced center of gravity, such an angle is often formed when entering tissues, so the maximum dimensions of the runway are formed already at the beginning of the wound channel.

When injured arrow-shaped elements, having low kinetic energy, uniform tissue damage is observed from the inlet to the outlet. When injured steel balls, cubes, fragments of a derivative form- by increasing the cross-sectional area - the greatest damage is observed in the area of ​​the inlet.

An important component of the formation of a gunshot wound is structure of damaged tissues. The wounding process as a phenomenon of energy transfer from a wounding projectile to tissues is a hydrodynamic phenomenon based on the cavitation effect. To the greatest extent, the cavitation effect is realized in tissues with high density containing a lot of liquid and enclosed in dense shells. Such tissues are muscles and parenchymal organs. Lungs, due to their low density and communication with the external environment, realize the effect of cavitation to the least extent. The impact of cavitation on hollow organs depends on the degree of their filling with liquid contents and gas.

The fourth factor is the effect of the vortex wake(a stream of vortex-like moving air and tissue particles) that occurs behind a wounding projectile. Particles of clothing, soil, microbes from the surrounding skin, etc. are absorbed into the wound.

Gumanenko E.K.

Military field surgery

test

Mechanism of education gunshot wound

The following elements can be distinguished in the structure of gunshot damage.

Entry gunshot wound. The moment a projectile hits an obstacle, it is accompanied by a whole range of mechanical effects. First of all, it generates the spread of kinetic energy in the direction of the bullet movement - a shock head wave, the speed of which approaches the speed of sound propagation in a given medium (in human soft tissues it is 1740 m/s).

Having a speed greater than the speed of the projectile, the shock bow wave affects soft tissues that have not yet been damaged, causing the formation of a molecular shock zone in them. Subsequently (if the victim lives), the tissues corresponding to this area become necrotic, so the actual amount of damage is much larger than the area of ​​the actual wound channel. The effect of the formation of a shock head wave also explains the formation of damage to soft tissues and bones far (outside the zone) of the passage of the wound channel.

The surface of the projectile is always contaminated to some extent. When introduced into the barrier, the pollution, rubbing against the edges of the wound, is superimposed on the belt of deposition in the form of a "rubbing belt", less often it goes beyond its limits. The composition of the rubdown belt includes soot, grease and metal. In this way, hallmarks the entrance gunshot wounds are a tissue defect ("minus"-tissue), a belt of rawness and a belt of rubbing.

wound channel. Penetrating into the barrier, the projectile forms a wound channel, causing a kind of pulsating oscillations of the wall in a direction transverse to the channel. Encountering an obstacle on its way (for example, a bone), the projectile can ricochet and change its direction, forming a broken wound channel. Passing through cavities or several parts of the body (for example, the shoulder-thorax), it can form a so-called interrupted wound channel.

Damage to a flat bone, the projectile forms a through hole in it in the form of a truncated cone. Its base faces the direction of the projectile, and the smaller diameter roughly corresponds to its caliber. When long tubular bones are damaged, predominantly radial cracks are formed in the projectile entry zone, and longitudinal cracks are formed at the exit site.

If the projectile damages a hollow organ containing fluid (for example, an overflowing bladder, the stomach filled with food, the heart during diastole), then the liquid, receiving kinetic energy due to the shock head wave, destroys the walls of the organ before they are hit by a projectile.

At a significant speed, passing near the bone, the projectile can form its fracture, morphologically similar to damage by a blunt object.

In rare cases, when a projectile gets stuck in the barrel when fired (poor-quality gunpowder), it can be ejected on a subsequent shot. When hit at a distance of several meters from such a "double" projectile, one gunshot wound is formed. In the wound channel, these projectiles are separated, and each of them separately forms further its own wound channel.

Exit gunshot wound. It is formed in those cases when the kinetic energy of the injuring projectile is sufficient to form a through wound channel. In the event of a bullet through the bullet in the process of its further flight, it can cause other damage, including the injury of another person.

Having reached the skin at the exit, the bullet, as it were, protrudes and stretches the skin, which is torn at the same time. The resulting exit gunshot wound has a slit-like shape. Quite often, its edges seem to be turned inside out. As a rule, they are uneven, but match when compared.

The exit gunshot wound does not have a defect in the tissue, belts of aggravation and wiping. Accordingly, there are no deposits of soot, powders and no metallization on the skin around it. Only in some cases, when the exit gunshot wound is formed in places where a dense object is pressed against the skin (dense coarse clothing, a belt, etc.), conditions arise for traumatizing the skin around the exit wound. The protruding area of ​​the skin seems to be squeezed and bent between solid objects (for example, a belt and the head of a bullet). There is a bruised area of ​​a round or oval shape, which. after drying, the skin may resemble a belt of sedimentation.

Features of gunshot wounds depending on the type of shells that caused them. Wounds caused by special-purpose bullets (tracer, incendiary, etc.) are in principle no different from ordinary bullet wounds, except for those cases when the wound is blind, and the pyrotechnic composition of the bullet continues to burn. In these cases, there are thermal lesions of the wound channel.

Damage from automatic weapons when firing a burst differ in their location: the entrance gunshot wounds are located on the same side of the body, have a similar direction and are located relatively close to each other. see Samishchenko S.S. Forensic Medicine. Textbook for law schools. 2006, p.89

Setting the distance of the shot. Depending on the distance at which the muzzle of the weapon is from the obstacle, it will be affected by all the components of the shot, part of them, or only the projectile.

A point-blank shot means such a gunshot injury when the muzzle of the weapon at the time of the shot is tightly pressed against an obstacle (clothes, skin). In this case, in accordance with the muzzle hole, the pre-bullet air knocks out a defect (hole) in it, into which the bullet enters, sliding along the side surface along the edges of the wound. Together with the bullet that forms the wound channel, the gases of the shot burst into it. Having a lot of pressure, they usually tear clothes crosswise, peel off the skin around the wound and, pressing it sharply against the cut of the weapon's barrel, form its imprint on it - a "punching mark".

For some weapon systems (submachine guns) that have a muzzle brake-compensator, it is impossible to fire at point-blank range. If the weapon is pressed against the barrier, it will not be the muzzle of the barrel that will rest against it, but the casing of the compensator brake. In such a situation, the deposition of soot from the shot is characteristic in accordance with the windows in the compensator. Since the gap between the muzzle brake and the obstacle is small (1-3 cm), a cruciform tissue rupture occurs due to the action of powder gases.

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