Altered Cell Notes
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Cellular adaptation is
reversible, structural, or functional response
Cells adapt to stressors to maintain homeostasis by
• Conserving resources • Decreasing or ceasing differentiated functions • Focusing exclusively on their own survival
Cells adapt to increased work demands by changing in
• Size (atrophy & hypertrophy) • Number (hyperplasia) • Form (metaplasia)
How can hypertrophy or hyperplasia be helpful?
Increase organ size so it can function better
How can hypertrophy or hyperplasia be harmful?
Increased organ size requires more blood supply. If not available, it becomes ischemic.
Morphologic cell changes
Helps a cell recover structure and function in response to a reversible injury
Most significant adaptive/morphologic changes include
Atrophy, hypertrophy, hyperplasia, and metaplasia
Atrophy
Decrease in cellular size caused by aging, disuse or lack of blood supply, hormonal stimulation, or neural stimulation.
What decreases with atrophy?
ER, mitochondria, and microfilaments. Decreases protein synthesis, increased protein catabolism, or both.
How is atrophy advantageous
Decreased organelles and size lowers oxygen requirements to survive
Hypertrophy
Increase in the size of cells caused by increased work demands or hormonal stimulation
What happens inside the cell with hypertrophy?
Increased amounts of proteins, ER, microfilaments, and mitochondria.
Hypertrophy can be classified as
Physiologic or pathologic
Hyperplasia
Increase in the number of cells caused by an increased rate of cell division.
What is hyperplasia classified as
Physiologic or pathologic
Physiologic Hyperplasia
Compensatory and hormonal
When does normal hyperplasia start/stop?
Stimulated by hormones or the need to replace lost tissues and ends when the stimulus is removed.
What is an example of hyperplasia?
Wound repair (increased cell division) Endometrium/breast: cell death triggers mitosis
Dysplasia/Atypical Hyperplasia
Abnormal change in size, shape, and organization of mature tissue cells. Not considered a true adaptational change but rather atypical.
Is dysplasia reversible?
Yes, cells can revert to normal after the stimulus causing it is removed
Cervical Dysplasia
Mild dysplasia: most regress on their own, most common form. Moderate & severe: Less likely to self-resolve and have a higher rate of progression to cancer.
Metaplasia
Reversible replacement of one mature cell type by another adult cell type
What does metaplasia allow for?
Substitution of cells that are better able to survive
What is an example of metaplasia?
Chronic smoking causing chronic irritation w/columnar tissue replaced by stratified squamous w/no cilia or mucus