Cellular Injury and Adaptation Pathology Morphology gross and

Cellular Injury and Adaptation

Pathology -Morphology : gross and microscopic changes of cell and tissue -Use ancillary techniques as : Histochemical, immunohistochemical, molecular and cytogenetics - This will result in signs & symptoms At the end : the pathologist will give a diagnosis and guide therapy. Pathology is the discipline that bridges clinical practice and basic science

The Cell and the Environment n Cells are constantly adjusting their structure and function to accommodate changes in their environment (stress stimuli) n Achieving a new steady state and preserving viability i. e. ADAPTATION n if the cell adaptive capability is exceeded cell injury develops

The Cell and the Environment Stimuli Cell Adaptation Cell Injury Reversible Irreversible (cell death) apoptosis necrosis

Causes of Cell Injury 1. Hypoxia: Ø Ø 2. Ø Obvious congenital malformations (Down syndrome) Subtle single amino acid substitution (hemoglobin S of sickle cell anemia) Nutritional Imbalances Ø 8. Allergic reactions, autoimmune diseases Genetic Defects Ø 7. Viruses, worms, bacteria …. . Immunologic Reactions Ø 6. Wide variety Microbiologic Agents Ø 5. Trauma, radiation, extremes of temperatures, electric shock Chemicals and Drugs Ø 4. ischemia (impaired blood supply) most common inadequate oxygenation of blood (cardio-respiratory failure) loss of oxygen carrying capacity (anaemia) Carbon monoxide poisoning Physical Agents Ø 3. (Oxygen deficiency) Mainly due to: Aging Deficiency of nutrients/ or excess

There are 4 main forms of Adaptation n Atrophy: decrease in size or number of cells leading to reduction in tissue mass n Hypertrophy: increase in size of cells leading to increase in size of organ n Hyperplasia: increase in number of cells leading to increase size of organ n Metaplasia: reversible change in which one adult tissue type is replaced by another

Cellular Adaptation to Injury n Physiologic n n Pathologic n n Responses to normal processes Allows cells to modulate environment and hopefully escape injury Cellular adaptive responses can occur at any of these Steps: n Receptor binding, signal transduction, protein transcription, translation, export

Atrophy n Definition: Shrinkage in the size of a cell by loss of cell substance n n Diminished cell function but cells are NOT dead Organ Atrophy n Results when a substantial number of cells are involved by: n Cell atrophy (cells living)

Atrophy n Causes n n n Decreased workload Loss of innervations Diminished blood supply Inadequate nutrition Loss of endocrine stimulation Aging

Atrophy n Biochemical Mechanisms n n § Decreased protein synthesis Increased protein catabolism (degradation) Or/ Both Morphology Decreased cell size n n n Atrophy represents a reduction in the structural components of the cells contain fewer mitochondria and myofilaments and a lesser amount of endoplasmic reticulum Increased autophagic vacuoles Increased residual bodies (lipofuscin)

Atrophy Normal

Kidneys, left side normal size right side atrophy