105

• Types of gangrenous necrosis and common presentations

  • Dry: coagulative necrosis - skin becomes dry, shrinks, colour changes to dark brown/back
  • Wet: neutrophils invade site - occurs in internal organs, causing site to become cold, swollen and black
  • Gas gangrene: clostridium- bacteria producing enzymes that destroy connective tissue
• Metaplasia


  The replacement of one cell type with another
• Dysplasia


  Deranged cellular growth, changes in cell size, shape, uniformity, etc
• Atrophy


  Decrease in the size or wasting away of a body part or tissue
• Hyperplasia


  Increase in the number of cells causing an increase in organ size
• Hypertrophy


  Increase in cellular size and functional capacity
• Causes of hypoxia


  • Reduced amount of oxygen in the air
  • Loss of hemoglobin or decreased efficacy of hemoglobin
  • Decreased production of red blood cells
  • Diseases of the respiratory and cardiovascular systems
  • Poisoning of the oxidative enzymes (cytochromes) within the cells
• Cystic Fibrosis


  • Autosomal recessive
  • Results in defective epithelial chloride ion transport
  • CF gene is located on gene 7
  • Classes 1-3 are considered more severe
  • Classes 4-6 are considered more mild
• Presentations of Cystic Fibrosis

  • Respiratory: thick, sticky mucous, chronic cough, infections, tachypnea, wheezing and crackles, hemoptysis, dyspnea on exertion
  • Gastrointestinal: obstruction, large oily stools, abdominal pain
  • Reproductive: male - congenital bilateral absence of the vas deferens, female - increase in thick cervical mucus that may lead to a decrease in fertility
• Down syndrome


  • IQ usually ranges from 20-70 (intellectual disability)
  • Virtually all males are sterile, some females can reproduce
  • Distinctive facial features include low nasal bridge, epicanthal folds, protruding tongue, low-set ears
  • Poor muscle tone (hypotonia) and short stature
  • Congenital heart disease (⅓-½ cases), reduced ability to fight respiratory tract infections, and increased susceptibility to leukemia - overall reduced survival rate - by age 40 years usually develop symptoms similar to those of Alzheimer's disease
  • About 75% of fetuses with DS abort spontaneously or are stillborn; 20% of infants die before age of 10, and those who live beyond 10 are only expected to live until age 60
  • 97% of cases are caused by nondisjunction during formation of one of parent's gametes or during early embryonic development - 3% result from translocations - in 95% of cases, nondisjunction occurs when mother's egg cell is formed; the remainder involve paternal nondisjunction; 1% are mosaics - these have a large number of normal cells, and effects of trisomic cells are attenuated and symptoms are generally less severe

  
• Examples of autosomal dominant diseases

  • Huntington's disease
  • Celiac disease
• Examples of disorders that are not autosomal dominant

  • Cystic fibrosis (autosomal recessive)
  • Down syndrome (neither dominant nor recessive)
  • Muscular dystrophy (autosomal recessive)
  • Cerebral palsy (autosomal recessive)
• Keloids


  • Considered a secondary lesion
  • Elevated, rounded, and firm
  • Clawlike margins that extend beyond the original site
• Hypertrophic scars


  • Elevated erythematous fibrous lesions that do not extend beyond the border of injury

  
• Both keloids and hypertrophic scars are caused by excessive collagen formation during dermal connective tissue repair
• Common inflammatory disorders of the skin

  • Eczema/dermatitis
  • Atopic Dermatitis
  • Diaper Dermatitis
  • Allergic Contact Dermatitis
  • Irritant Contact Dermatitis
• Atopic Dermatitis


  • Most common form of eczema in children
  • Genetic link, altered immunity, and immune responses
  • Filaggrin gene mutation
• Atopic Dermatitis clinical manifestations

  • Severe pruritus, eczematoid appearance, age-dependent distribution of skin lesions
  • Young: rash to face, scalp, trunk, arms, and legs
  • Older: rash to neck, antecubital, and popliteal fossae, hands and feet
• Diaper Dermatitis


  • Form of irritant contact dermatitis
  • Prolonged exposure to irritation by urine and feces, maceration by wet diapers, airtight plastic diaper covers
  • Often secondarily infected with candida albicans
  • Affects the lower aspect of the abdomen, genitalia, buttock, and upper portion of the thigh
• Allergic Contact Dermatitis


  • Caused by t-cell-mediated or delayed hypersensitivity
  • Allergen comes in contact with the skin, binds to a carrier protein to form a sensitizing antigen; langerhans cells process the antigen and carry it to t cells, which become sensitized to the antigen
• Allergic Contact Dermatitis manifestations

  • Erythema
  • Swelling
  • Pruritus
  • Vesicular lesions
• Irritant Contact Dermatitis


  • Caused by activation of the innate immune system
  • Severity related to concentration of the irritant, length of exposure, and disruption of the skin barrier
• Types of skin conditions commonly found in children

  • Atopic dermatitis
  • Chicken pox (rubella)
  • Warts: benign lesions caused by HPV
• Skin reactions to allergens

  • Allergic contact dermatitis
  • Cutaneous vasculitis: inflammation of the blood vessel walls resulting from immune complexes in small blood vessels
  • Urticaria: circumscribed area of raised erythema and edema of the superficial dermis
• Alkali burns


  Cause little pain but extensive damage by liquefaction necrosis: breakdown of protein and collagen, saponification of fats, dehydration of tissues, thrombosis of blood vessels
• Acid burns


  Cause immediate pain and coagulation necrosis; deeper tissue typically is not injured
• Superficial (1st degree) burns


  • Only epidermis is affected
  • Skin is red
  • Painful
  • Example: sunburn
• Partial thickness (2nd degree) burns

  • Epidermis and dermis are affected
  • Superficial: skin is red, blisters, moisture present, painful, heals spontaneously
  • Deep: extends to dermis, damages hair follicles and sweat and sebaceous glands, very painful
• Full thickness (3rd degree) burns


  • All layers of the skin are destroyed
  • Skin appears white and pale, brown and leathered, or charred
  • No pain (nerve endings damaged)
• Presentations of smoke inhalation and inhalation burns above the glottis

  • Presence of facial burns
  • Singed nasal hair
  • Hoarseness, painful swallowing
  • Darkened oral and nasal membranes
  • Carbonaceous sputum
  • History of being burned in an enclosed space
  • Clothing burns around chest/neck
• Presentations of smoke inhalation and inhalation burns below the glottis

  • Edema (may not be present until 12-24 hours after the burn)
  • Acute respiratory distress syndrome

  
• Pre-hospital care for burns

  1. Remove person from source of burn

  2. Stop burning processes

  3. Electrical: remove from source, ensure power is off, look for entrance and exit wounds

  4. Chemical: brush solid particles off the skin, immediately flush exposed area with water

  5. Thermal: small - cover with clean, cool, tap water dampened towel (<10%); large - if unresponsive, CAB, if responsive, ABC, do not immerse in cool water or use ice, remove burned clothing and wrap in a clean, dry, sheet or blanket

  6. Inhalation: observe for signs of respiratory distress or compromise, treat quickly

  7. Manage airway, fluid resuscitation, remove jewelry
• Emergent (resuscitative) phase of burns


  1. Resolves immediate problems resulting from the injury, usually lasts up to 72 hours

  2. Primary concerns are the onset of hypovolemic shock and edema

  3. Fluid and electrolyte shifts, greatest threat is hypovolemic shock caused by massive shift of fluids out of blood vessels as a result of increased capillary permeability, colloidal osmotic pressure decreases, resulting in more fluid shifting out of the vascular space into the interstitial spaces, second spacing, decreased BP, increased HR, normal insensible loss: 30-50mL/hour

  4. Inflammation, healing, immunological changes - burn injury causes widespread impairment of the immune system, skin barrier is destroyed, bone marrow is depressed, circulating levels of immune globulins are decreased, WBCs develop defects

  
• Clinical manifestations of emergent phase of burns


  • Shock from pain and hypovolemia
  • Blisters
  • Adynamic ileus – functional paralysis to GI tract
  • Shivering
  • Altered LOC

  
• Complications of emergent phase of burns

  • Cardiovascular system: dysrhythmias and hypovolemic shock, impaired circulation to extremities, tissue ischemia, necrosis, impaired microcirculation, increased viscosity – sludging
  • Respiratory system: upper respiratory tract injury - edema formation, mechanical airway obstruction and asphyxia, lower airway (inhalation) injury - direct insult at the alveolar level, interstitial edema, pneumonia, pulmonary edema
  • Urinary system: decreased blood flow to the kidneys causes renal ischemia, acute tubular necrosis (ATN)

  
• Cellular immunity


  Produces T cells that attack and destroy invaders
• Humoral immunity


  The B cells produce antibodies to fight off infection or toxins
• Multiple Sclerosis pathophysiology


  • An autoimmune disorder that attacks the myelin sheath of the brain and cord, leading to scarring
  • Attacks and remissions (can get worse or better at certain times)
  • Progressive, inflammatory, demyelinating disorder of the CNS
  • Loss of myelin disrupts nerve conduction with subsequent death of neurons and brain atrophy
  • Paresthesia, weakness, impaired gait, visual disturbances, or urinary incontinence, cerebellar and corticospinal involvement, intention tremor, slurred speech
  • Four subtypes: remitting-relapsing, primary-progressive, secondary-progressive, progressive-relapsing
  • Diffuse & progressive - patches of damage can occur throughout the brain and spinal cord
  • Autoreactive T cells and B cells cross the blood brain barrier, recognize myelin & oligodendrocyte autoantigens, inflammation is triggered and loss of oligodendrocytes occur
  • Micolia cell activation - inflammation and injury with plaque formation and axonal degeneration

  
• ALS pathophysiology


  • The death of voluntary motor neurons
  • Progressive, neurodegenerative disorder of upper and lower motor neurons of the corticospinal tract
  • Death is common within 3-5 years
  • Most cases are idiopathic, but can also be a genetic mutation
  • Signs and symptoms: muscle cramps, twitching, spasticity, gradual worsening muscle weakness over time, difficulty with ambulation, speaking, swallowing, and eventually breathing
• Parkinson's disease pathophysiology


  • When the substantia nigra (the portion of the brain that produces dopamine) becomes damaged
  • Involves a degeneration of dopamine-producing neurons in substantia nigra of the midbrain
  • Disrupts dopamine-acetylcholine balance in basal ganglia
  • Slowing down in the initiation and execution of movement
  • Increased muscle tone
  • Tremors at rest
  • Impaired postural reflexes