Pathology unit 3

• Unit 3 Task


  1. Differentiate between Aerobic and anaerobic energy production

  2. Define the term "Homeostasis"

  3. Differentiate between a 'stress" and adaptation"

  4. Briefly explain the following cellular adaptations:

  5. 4.1. Hypertrophy

  6. 4.2. Hyperplasia

  7. 4.3. Atrophy

  8. 4.4. Metaplasia

  9. List the causes of cell injury
• Aerobic energy production


  Aerobic glycolysis- energy liberated from glucose, occurs in the mitochondria (with O2), supplies 90% of the body's energy needs, requires the heart, lungs and all of the circulatory system to work efficiently, obtained from using the large stores of glycogen in the body, synthesized into ATP, may also be obtained through breakdown of fats, proteins and carbohydrates (requires more O2), by products = CO2 and H2O (easily released from the body)
• Anaerobic energy production


  Occurs in the cytoplasm (without O2), obtained through glycolytic process, NB pathway during periods of ↓ O2 and cells that lack mitochondria, Glucose → Pyruvic acid or Ethyl alcohol, by products = lactic acid (toxic and thus must be broken down – this is achieved by the liver), NB: Lactic acid ↑ with strenuous exercise, heart failure, severe infection, shock OR when the liver is damaged or diseased
• Homeostasis


  Equilibrium of the micro-environment of the cell, every cell is involved, change at a cellular level can affect the entire body, any external stressor can disrupt homeostasis thus leading to illness
• Stress


  Any demand on the cell which requires adaptation
• Adaptation


  Adaptations are reversible changes in size, number, metabolic activity or functions of cells in response to changes in their environment, preservation of viability and function by drawing on cell reserves
• Cellular adaptations to stress

  • Can be PHYSIOLOGICAL OR PATHOLOGICAL, elimination of the stress can result in the cell returning to its original state WITHOUT harmful consequences
• Hypertrophy


  Increased cell and thus organ size, often in response to increased workload OR induced by mechanical stress and by growth factors, involves an increase in functional components, occurs in tissues incapable of cell division (cardiac and muscle tissue), can occur due to normal physiological changes or pathological changes (compensatory or adaptive)
• Hyperplasia


  Increase in number of cells in a tissue or organ, occurs in tissues whose cells are able to divide (e.g. epidermis, epithelium of the intestinal tract and glandular epithelium), can involve activation of genes controlling cell proliferation, controlled process occurring in response to an appropriate stimulus, normal physiologic (hormonal = uterine / breast enlargement, compensatory = after partial hepatectomy - healing of connective tissue), NB most pathologic forms of hyperplasia occurs as a result of excessive hormonal OR growth stimulation
• Atrophy


  Decreased cell and thus organ size, cells have less mitochondria, endoplasmic reticulum etc - decreased protein synthesis due to ↓ metabolic activity, due to a decrease in workload or adverse environmental conditions – O2 consumption and protein synthesis ↓, involvement of sufficient number of cells = tissue atrophy, general causes: disuse, denervation, loss of endocrine stimulation, inadequate nutrition, ischaemia or decreased blood flow
• Metaplasia


  If the cell cannot adapt OR the stimulus is strong enough to cause injury like ischaemia, toxicity and infections, CELL INJURY DEVELOPS
• Causes of Cell injury

  • Toxic (endogenous - metabolic errors, gross malformations, hypersensitivity reactions; exogenous - chemical - alcohol, lead, carbon monoxide, pesticides, drugs that alter cellular function)
  • Infectious (exogenous - viral, bacterial, fungal, protozoa)
  • Physical (exogenous - thermal - radiation, electrical, extreme temperatures; mechanical - trauma or surgery - injured blood vessels, fractured bones etc.)
  • Deficit injury (lack of H20, lack of O2 - hypoxia, ischaemia, lack of nutrients OR excesses in nutrition)
  • Immunologic reactions
  • Genetic defects – due to deficiency of functional proteins
  • Aging