Pathology: General

Aiman Zaher

• Éditeur: QuickStudy Reference Guides
• Année: 2009
• ISBN:
  9781423237860
• Sujet: Medizin
• Sous-sujet: Pathologie

Quick reference to Pathology, the basic cellular response to injuries, with succinct definitions ensuring this guide covers in 6 pages what you would usually find in 30 pages or more. This can be combined with the companion guides Pathology Systemic 1 and 2, putting these concise 6 page guides together for a solid 90 pages of information in 18 pages.

Environmental & Nutritional Disorders

Mechanical Injury

• Varied causes (e.g., sharp objects, bullets)
• Produces tissue damage
• Possible death due to renal failure, septic shock, ruptured abdominal aortic aneurysm, and pulmonary embolism
• Skin and soft tissue injuries
  • Incision: A clean cut by a sharp object
  • Abrasion or scrape: Superficial tearing of the skin
  • Laceration: A jagged tear, which usually extends to the underlying tissue
  • Puncture: A deep, tubular wound
  • Contusion: A bruise caused by injury to the blood vessels of the skin, organs, or both
• Blunt force injuries
  • Head injury: Brain damage due to direct external injury or intracranial hemorrhage; brain contusion at the point of impact (coup injury) or on the opposite side of the brain (contrecoup injury)
  • Abdominal injury: Rupture of abdominal organs (e.g., spleen, liver) and contusion
  • Thoracic injury: Rib fracture, pneumothorax, and lung injury
  • Clots formed from hemorrhage by blunt force injuries may lead to embolism and/or infarction

Thermal Injury

• Thermal injury from heat
  • Classification
    • First-degree burns (partial-thickness burns)
      • Hyperemia without significant epidermal damage
      • Generally heal without intervention
    • Second-degree burns (partial-thickness burns)
      • Blistering and destruction of the epidermis
      • Slight damage to underlying dermis
      • Generally heal without intervention
    • Third-degree burns (full-thickness burns)
      • Damage to the epidermis, dermis, and dermal appendages
      • Skin and underlying tissue often charred and blackened
      • Often require skin grafting
  • Superficial burns
    • First- and second-degree burns
    • Epithelium can regenerate
  • Deep burns
    • Third-degree burns
    • All of the epithelium destroyed; dermis and appendages damaged
    • Heal by scarring
  • Complications
    • Inhalation of smoke or toxic fumes
    • Severe dehydration
    • Curling ulcer: Acute gastric ulcer associated with severe burns
    • Infection: Common cause of death in burn victims; most frequent organism is Pseudomonas aeruginosa
• Thermal injury from cold and freezing
  • Pathogenesis: Vasoconstriction leads to endothelial damage with thrombosis and ischemia
  • Frostnip: Prolonged immersion in cold leads to endothelial damage with edema and swelling due to leakage of fluid
  • Frostbite
    • May be localized and usually affects exposed areas (fingers, toes, earlobes, nose)
    • Effects of severe, prolonged frostbite
      • Erythema and pruritus
      • Intracellular ice crystals
      • Intravascular thrombosis
      • Possible local gangrene
    • May be generalized; leads to death

Electric Injury

• Electric current passes through an individual and electric circuit completed
• Mortality caused by current passing through the brain or heart
• Morbidity
  • Respiratory diseases
  • Cardiac arrest and arrhythmias
  • Small cutaneous burns with blister (vesicle, bulla) formation at point of entry or exit of the electric current
  • Burns may be severe

Radiation Injury

• UV radiation injury
  • Mostly sun damage to skin and eyes
  • Mechanism: Absorption of UV light by DNA causes DNA fractures or changes in sequences
  • Damage increases with increased UV exposure
  • Increased melanin is protective (diminishes the amount of UV absorption)
  • Acute injury of skin
    • Sunburn (first-degree burn)
    • Delayed vascular dilation causes erythema
    • Often superficial desquamation
    • Severe cases have blister formation
  • Chronic injury of skin
    • Collagen and elastic tissue damage
    • Epithelial changes
      • Cosmetic damage: wrinkling
      • Precancerous lesions: actinic keratosis
      • Cancerous lesions: basal cell carcinoma, squamous cell carcinoma, melanoma
  • Genetic predisposition: The effect of UV radiation injury will be exaggerated by genetic disorders (e.g., xeroderma pigmentosum)
    • Defect in DNA repair mechanisms causes sensitivity to UV light
    • Results in many skin conditions: scales and crusts, atrophy, poikiloderma, freckles (ephilides), actinic keratosis, early skin cancers
    • Treatment: protect from or avoid UV light
• Ionizing radiation injury
  • Mechanism
    • Exposure to short-wavelength, high-frequency radiation
      • High- and low-dose therapeutic, occupational, and diagnostic X-rays and γ-rays
      • Particulate radiation: electrons, protons, and neutrons
      • Radioactive waste, nuclear disasters, atomic bomb radiation
      • Transfer of energy to molecules through ionization
      • Molecules are reactive and capable of damaging cells
      • Toxic free radicals affect vital cell components (DNA, intracellular membranes, cell membranes, other cellular organelles)
    • Damage to the DNA
      • Direct action (hit) on vital molecule
      • Indirect action: ionization of water can produce free radicals, which leads to damage to vital molecules
      • Damage repairable but very slow
    • Damage dependent on the total dose, rate of delivery, and type of tissue irradiated
  • Repair: DNA has the ability to repair itself
  • Radiosensitivity of specialized cells
    • Most susceptible: tissues with a high mitotic rate, rapid turnover, or both
    • Earliest blood cells to be affected: lymphocytes
    • Most sensitive (regularly and actively divide): lymphoid, hematopoietic, germ, GI mucosal, and rapidly dividing tumor cells
    • Intermediately sensitive: fibroblasts and cells of the endothelium, elastic tissue, salivary glands, and eye
    • Resistant (division ceases after fetal development): cells of bone, cartilage, muscle, CNS, kidney, liver, and most endocrine glands
  • Role of distribution and dosage in the effect of ionizing radiation
    • 50 Gy (5000 rad) to any one body region
      • No severe or lethal consequences
      • May be minor changes; therapeutic irradiation to the jaw may cause obliterative endarteritis to the salivary glands and bone
    • 3 Gy (300 rad) to the whole body leads to up to 50% chance of death
    • 10 Gy (1000 rad) to the whole body leads to 100% chance of death
  • Localized ionizing radiation i...