Pathogenic Effects of Environmental Factors: Detailed Study Guide

Classification of Pathogenic Irritants by Origin

  • Irritants are categorized based on their source and nature into four fundamental types:
    • Physical stimuli
    • Chemical irritants
    • Biological irritants
    • Psychosocial stimuli

Physical Stimuli and Mechanical Factors

  • Physical stimuli encompass a wide range of environmental conditions and forces:

    • Mechanical forces
    • Thermal factors
    • Electric current
    • Radiation
    • Accelerations
    • Weightlessness
    • Acoustic waves
    • Changes in atmospheric pressure

  • Mechanical Factors:

    • These act on the human body in two distinct ways:
      • The body itself moves and impacts an object.
      • Mechanical bodies or objects move against the body.
    • Determinants of Disability: The severity of the damage depends on several variables:
      • The weight of the object.
      • The speed of contact.
      • The specific type of mechanical factor.
      • The angle of interaction on the body.
    • Types of Damage:
      • Abrasion (Excoriacio).
      • Bruise (contusio).
      • Bruising (hematoma).
      • Wounds (vulnera).
      • Dislocation of joints (lucsatio).
      • Fracture (fissure or fracture).
    • Bleeding (Hemorrhage):
      • This is the primary consequence of mechanical action.
      • The severity depends on the volume of blood lost and the rate of blood loss.
      • Blood loss up to 18−20%18-20\% is generally not life-threatening.
      • Blood loss exceeding 25%25\% is considered life-threatening.
      • The major complication associated with severe mechanical trauma is traumatic shock.

Thermal Factors: High and Low Temperature Action

  • High Temperatures:

    • Local Damage: Expressed as burns (Combuscio) ranging from I to IV degree.
    • General Complication of Local Damage: Burn shock, characterized by massive plasma loss.
    • General High Temperature Action: Results in overheating, leading potentially to heat stroke.
    • Overheating occurs in two distinct phases:
      • Compensated Phase: Characterized by increased heat loss and reduced heat production; the internal body temperature remains normal.
      • Decompensated Phase: Characterized by the failure of thermoregulatory mechanisms, leading to an increased body temperature.

  • Low Temperatures:

    • Local Damage: Expressed as frostbite (congelacio) ranging from I to IV degree.
    • Common Complication of Local Damage: Shock resulting from frost.
    • General Action (Hypothermia): Cooling of the body, which develops in two phases:
      • Compensated Phase: Characterized by reduced heat loss and increased heat production; body temperature remains normal.
      • Decompensated Phase: Thermoregulatory mechanisms fail; body temperature drops below 35∘C35^{\circ}C. Symptoms include drowsiness, hallucinations, and the phenomenon known as "white death."
    • Hibernation: This is a purposeful lowering of body temperature to 31−32∘C31-32^{\circ}C using external cooling and medications that suppress the nervous system. It is utilized during severe heart operations when extracorporeal blood circulation is not possible.
    • Colds: Low temperatures reduce both general and local reactivity and resistance, creating an environment favorable for bacterial and viral infections.

Pathogenic Effects of Electric Current

  • Types of Damage:
    • Electrical Trauma (Electrocution): Damage from household mains electricity or high voltage.
    • Atmospheric Electricity Damage: Lightning (fulminacio).
  • Factors Influencing Damage:
    • Current voltage.
    • Type of current and resistance.
    • Entry point into the body and the duration of exposure.
    • Most damage is caused by currents with a strength over 50 mA50\,mA, voltage under 250 V250\,V, and alternating current (AC) with a frequency of 40−60 Hz40-60\,Hz.
  • Modes of Interaction:
    • Biological: Shuddering and seizures.
    • Electrothermal: Combustion/burns.
    • Electrochemical: Polarization of mobile particles within the cell.
    • Electromechanical: High voltage can cause wounds, lacerations, or the detachment of body parts.

Radiation: Electromagnetic Waves and Ionizing Rays

  • Sources of radiation can be natural or artificial.

  • Visible Spectrum: Waves between 400−700 nm400-700\,nm; prolonged action can lead to retinal damage and blindness.

  • Infrared Rays: Wavelengths between 760 nm−1 mm760\,nm - 1\,mm; cause burns and heat stroke.

  • Ultraviolet (UV) Rays: Wavelengths between 400 nm−10 nm400\,nm - 10\,nm; prolonged irradiation causes denaturation of proteins and destruction of nucleic acids, lipids, and proteins.

  • Lasers: Monochromatic waves characterized by directionality, brightness, and the ability to focus high energy on small areas. They can cause burns or gunshot-like wounds.

  • Ionizing Rays: Includes X-Rays, Alpha/Beta/Gamma rays, and Radiation consisting of neutrons, protons, and positrons. These ionize the medium they pass through.

  • Radiation Sickness:

    • Occurrence depends on the dose and exposure time.
    • Acute Radiation Sickness: Occurs when a large dose is accumulated in a short time (e.g., nuclear explosion or power plant accident).
      • Irradiations exceeding 10 Gy10\,Gy lead to three lethal forms: Cerebral, Toxic, and Gastrointestinal.
    • Chronic Radiation Sickness: Dose accumulates over a long period (e.g., working in radiology or nuclear power).
      • Progression is slow, with diverse symptoms that are difficult to reverse.
    • General Symptoms: Asthenia, physical and mental fatigue, tendency toward infections, and menstrual disorders in women.
    • Pathogenesis (2 Phases):
      • Primary Phase: Ionization of water in cells forming positive and negative water ions, which break down into free radicals such as OO, H2O2H_2O_2, and hydroperoxide.
      • Secondary Phase: Products of primary radiolysis (radiotoxins) bind to body molecules, enhancing ionization.
      • Mechanisms: Free radicals convert sulfhydryl groups of thiol enzymes, inactivating them and impairing nucleic acid synthesis. This primarily affects "young cells" such as blood, sexual, and epithelial cells.

Accelerations, Weightlessness, and Acoustic Waves

  • Accelerations:

    • Kinetosis: A complex of disorders arising from rapidly changing, uneven accelerations during transport or spaceflight.
    • Caused by stimuli to the vestibular apparatus, visual analyzer, and autonomic receptors in the mucous membranes of the stomach and intestines.

  • Weightlessness:

    • A factor specific to cosmonauts. The primary pathogenetic factor is the lack of hydrostatic blood pressure.

  • Acoustic Waves (Sound):

    • Human hearing perceives sound between 1616 and 20,000 Hz20,000\,Hz at intensities from 00 to 140 dB140\,dB.
    • Infrasound: Frequencies below 16 Hz16\,Hz. Symptoms include headache, irritability, and easy fatigue.
    • Ultrasound: Frequencies above 20,000 Hz20,000\,Hz. High-frequency damaging ultrasound from generators acts via mechanical, thermal, and chemical mechanisms.
    • Noise: A combination of chronically changing complex tones with intensity-based effects:
      • 50 dB50\,dB: Irritating and distracting.
      • >70 dB>70\,dB: Difficult to tolerate.
      • 85−115 dB85-115\,dB: Found in discos; damages the hearing aid and psyche.
      • 115−140 dB115-140\,dB: Found at airports; causes disturbances in the CNS, CCS, endocrine system, and auditory analyzer.

Changes in Atmospheric Pressure

  • Low Atmospheric Pressure (Hypobaria):

    • Mountain Sickness: Result of reduced partial pressure of oxygen (pO2pO_2) in ambient air.
    • Decompression Effects: Caused by the equalization of pressure in gas-containing organs or the transition of dissolved gases in the blood into a gas state (gas embolism or caisson sickness).

  • High Atmospheric Pressure (Hyperbaria):

    • Occurs in divers and caisson workers.
    • Mechanisms of Damage: Mechanical action of the hyperbaric medium (water/gas) and the physicochemical effects of inhaled gases.

Chemical Factors

  • Toxicity depends on chemical structure, active groups, and radicals.
  • Classification: Organic, inorganic, toxic gases, and medications in toxic doses.
  • Determinants of Damage:
    • Type and dose of the agent.
    • Mode of penetration and solubility in biological fluids.
    • Method of elimination.
    • Formation of metabolites (mainly in the liver).
    • State of the liver's detoxifying function.
    • Body habituation (e.g., tolerance to alcohol or drugs).

Biological factors

  • Includes: Pathogenic microorganisms (bacteria, viruses, rickettsiae, spirochetes), parasites, insects, fish, and reptiles.
  • Microorganism Qualities: Pathogenicity, infectiousness, virulence, and contagiousness.
  • Bacterial Damage Mechanisms:
    • Through enzymes (e.g., hyaluronidase, collagenase).
    • Through exo- and endotoxins.
    • Via antigenic and pyrogenic properties.
  • Viruses: Enter host cells, use host energy, multiply, and alter metabolism and antigenic properties.
    • Viral Diseases: Influenza, Mumps, Hepatitis, Measles, HIV, Hemorrhagic fever.
  • Parasites: Protozoa, helminths, and tapeworms.
    • Mechanisms: Direct cell damage, intoxication of the body, and allergy induction.
  • Arthropods (Vectors):
    • Mosquitoes carry malaria plasmodium and yellow fever.
    • Others carry viral encephalitis, Lyme disease, and hemorrhagic fever.

Psycho-emotional Factors

  • Emotional stress is often based on mental overstrain from social conflicts.
  • Speech as a factor:
    • Positive: Can improve the psyche of healthy and sick individuals.
    • Negative: "Ill-considered statements" by medical personnel can cause iatrogenic diseases or worsen a patient's prognosis.