Cellular and Tissue Adaptation
Dr. Raid Jastania
Stress
Injury
Cell Injury
Cell Death
Response
Adaptation
Cell Adaptation
• Cellular Adaptation in Growth and Differentiation
• Subcellular Responses to Injury
• Intracellular Accumulation
• Pathologic Calcification
Cellular Adaptation in Growth and Differentiation
• Atrophy:• Atrophy is shrinkage in the size of cells
(and the organ) due to loss of cell substance.
• apoptosis. • Causes: decrease in work load,
immobilization, loss of innervation, diminished blood supply, nutrients, or loss of endocrine stimulation and aging.
Atrophy
• Atrophy may occurs in any organ or tissue.
• Example: muscle atrophy due to paralysis or immobilization.
• Atrophy results when the production of cellular substance is less than the degradation. Degradation can occur in lysosomes or in ubiquitin-proteasome system.
• Hypertrophy:• Hypertrophy is the increase in the size of
cells (and organs) • caused by increased functional demand. • Example: Left ventricular hypertrophy due
to hypertension. Hypertrophy can result from mechanical stress or hormonal stimulation.
• Hyperplasia:• Hyperplasia is increase in the number of
cells in an organ.
• It can be physiological. Example: hormonal hyperplasia of breast during lactation.
• It can be pathological. Example: Hormone imbalance and endometrial hyperplasia.
Hypertrophy/Hyperplasia
• Metaplasia:• Metaplasia is a reversible change of one adult cell
type to another adult cell type.• Example: change of the respiratory mucosa in the
respiratory tract from the ciliated culomnar epithelium to squamous epithelium due to smoking.
• This change results from “genetic reprogramming”.
Subcellular Responses to Injury
1. Lysosomal catabolism: heterophagy, Autophagy
2. Hypertrophy of Smooth Endoplasmic Reticulum: increase in the ability of the cell to metabolize substance. This results in “drug tolerance”. Example: tolerance to Barbiturates, and Alcohol.
3. Mitochondrial Alteration: Example: increase or decrease in the number of mitochondria.
Subcellular Responses to Injury
4. Cytoskeletal Abnormalities: Occur in hypertrophy and atrophy of the cells.
5. Heat Shock Proteins: HSP are proteins involved in protein folding, disaggregation and transport. The production of HSP is increased in stress situations (injury).
Intracellular Accumulation:
1. Fatty Change: Defect in fat metabolism. This commonly occurs in alcoholics due to altered SER function and in toxicity with CCl4.
2. Cholesterol: is accumulated in histiocytes following ingestion of cellular parts in necrosis
3. Protein: Example: Mallory bodies in liver cells.
Intracellular Accumulation:
4. Glycogen: Example: diabetes mellitus in liver
5. Pigment: exogenous like carbon, and endogenous like: melanin, lipofuscin, and hemosiderin.
Pathologic Calcification:
1. Dystrophic calcification: occurs following tissue necrosis (and commonly inflammation). Example: calcification in atheroma.
2. Metastatic calcification: occurs in normal tissue as a result of high Ca++ level in the blood. Causes:
1. high PTH, 2. Renal failure3. Bone destruction4. Vit D intoxication.