Cellular Adaptation Overview

Study Notes

Cellular adaptations are changes cells make in response to environmental changes.
Cells can adapt in various ways:
- Atrophy: Reduction in cell size and number due to decreased workload, blood supply, nutrition, or endocrine stimulation.
- Hypertrophy: Enlargement of individual cells due to increased workload or abnormal stressors.
- Hyperplasia: Increase in cell number due to normal (physiologic) or abnormal (pathologic) stressors.
- Metaplasia: Reversible change where one mature cell type is replaced by another. Can be physiologic or pathologic.
- Dysplasia: Disordered growth of cells.
- Anaplasia: A lack of differentiation in cells, associated with cancer.
- Neoplasia: Abnormal, uncontrolled growth of cells, leading to tumor formation.

Physiologic Hyperplasia: Occurs due to a normal stressor, e.g., breast enlargement during pregnancy, thickening of the endometrium during the menstrual cycle.
Pathologic Hyperplasia: Occurs due to an abnormal stressor, e.g., endometrial hyperplasia due to prolonged estrogen stimulation.

Physiologic Hypertrophy: Occurs due to a normal stressor, e.g., skeletal muscle enlargement with exercise.
Pathologic Hypertrophy: Occurs due to an abnormal stressor, e.g., heart enlargement due to aortic stenosis.

Physiological Metaplasia: Example is cervical ectopy.
Pathological Metaplasia: A response to chronic stimuli, can regress or become malignant.

Oxygen Deprivation (Hypoxia & Ischemia): Lack of oxygen leads to impaired cellular function and death.
Free Radicals: Reactive molecules damage cellular structures.
Chemical Agents: Many chemicals can cause cell damage, e.g., glucose, hypertonic saline, poisons.
Physical Agents: Trauma, extreme temperatures, radiation, and electric shock can injure cells.
Infections: Pathogens can damage cells directly or through immune responses.
Immune Reactions: Immune system responses, like autoimmune disorders, can damage tissues.
Genetic Defects: Mutations, chromosomal abnormalities, and enzyme deficiencies can lead to cell injury.
Nutritional Defects: Deficiencies in proteins, enzymes, or excesses in cholesterol can contribute to cellular damage.
Aging: Natural aging processes can lead to cellular changes and decline in function.

Regeneration: Replacement of damaged cells with new, identical cells, maintaining function.
Replacement: Replacement of damaged cells with connective tissue when regeneration is not possible. Connective tissue provides structural support, but doesn't restore full function.

Regeneration involves the production of new parenchymal cells (the functional cells of an organ).
This process restores the organ's structure and function.

This involves the replacement of damaged cells with stromal cells (cells that provide support to parenchymal cells).
Replacement maintains the tissue/organ structure but doesn't restore full functionality.