Pathology of Atrophy and Metaplasia

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Questions and Answers

What is a constant feature of all forms of cell injury except Apoptosis?

Complete loss of DNA

Rapid cell proliferation

Loss of mitochondrial function

Increased membrane permeability (correct)

What is the main consequence of damage to the plasma membrane?

Osmotic balance loss (correct)

Improved cell rigidity

Enhanced cellular communication

Increased ATP production

Which membrane alteration is typically associated with reversible cell injury?

Complete rupture of cell membrane

Hydropic change or vacuolar degeneration (correct)

Apoptotic body formation

Increased extracellular matrix production

What triggers the initiation of Apoptosis in cells?

Accumulation of misfolded proteins Signup and view all the answers

What is the consequence of lysosomal membrane damage?

Leakage of enzymes into cytoplasm Signup and view all the answers

What are the major causes of ATP depletion?

Reduced supply of oxygen and nutrients Signup and view all the answers

What is a consequence of mitochondrial damage?

Release of cytochrome c into the cytosol Signup and view all the answers

How does increased intracellular calcium influence cell health?

It can activate apoptosis by direct activation of caspases. Signup and view all the answers

What defines oxidative stress?

An excess of free radicals in cells. Signup and view all the answers

What is a free radical?

An unstable atom with a single unpaired electron. Signup and view all the answers

Which of the following is NOT a way to remove free radicals?

Photodynamic therapy Signup and view all the answers

Which pathological effect is caused by free radicals?

Lipid peroxidation in membranes Signup and view all the answers

What triggers the generation of free radicals in neutrophils and macrophages?

Destruction of ingested microbes and substances Signup and view all the answers

What is atrophy characterized by?

Reduced cell size Signup and view all the answers

Which type of atrophy occurs during normal development?

Gravid uterus atrophy Signup and view all the answers

What mechanism primarily contributes to protein degradation in atrophy?

Ubiquitin-proteasome pathway Signup and view all the answers

What type of metaplasia involves the replacement of ciliated columnar epithelium?

Columnar to Squamous Signup and view all the answers

What can persistent factors causing metaplasia lead to?

Malignant transformation Signup and view all the answers

Which mechanism is involved in the cellular response to injurious stimuli?

Nature of the injury Signup and view all the answers

What can lead to irreversible cell injury?

Prolonged and damaging stress Signup and view all the answers

What is a key characteristic of metaplasia?

Reversible change of one cell type Signup and view all the answers

What is the standard environment that a cell looks to maintain for proper function?

Homeostasis Signup and view all the answers

What type of cellular adaptation is characterized by an increase in cell size?

Hypertrophy Signup and view all the answers

What is the primary cause that can lead to hypertrophy?

Increased functional demand Signup and view all the answers

Which type of hyperplasia occurs in cells capable of dividing?

Pathologic hyperplasia Signup and view all the answers

What type of hyperplasia is often hormonally induced?

Physiological hyperplasia Signup and view all the answers

Which organ is commonly associated with pathological hypertrophy due to increased workload?

Heart Signup and view all the answers

In which type of cellular adaptation does the structure change to a different differentiated cell type?

Metaplasia Signup and view all the answers

What results when both hypertrophy and hyperplasia occur in a tissue?

Increased tissue mass Signup and view all the answers

Study Notes

Atrophy

Reduced size of cell, tissue, or organ due to loss of cell substance
Two types: physiologic and pathologic
Physiologic atrophy occurs during normal development, such as the involution of the gravid uterus.
Pathologic atrophy can be caused by:
- Decreased workload (disuse atrophy)
- Loss of innervation (denervation atrophy)
- Diminished blood supply
- Inadequate nutrition
- Loss of endocrine stimulation (loss of estrogen)
Mechanisms of atrophy:
- Decreased protein synthesis and increased protein degradation
- Degradation of cellular protein caused by the ubiquitin-proteasome pathway
- Increased autophagy

Metaplasia

Reversible change in which one differentiated cell type is replaced by another cell type
The new epithelium is better suited to dealing with the current stress or irritation
Persistence of factors causing metaplasia may lead to progression into malignant transformation
Most common epithelial metaplasia is columnar to squamous, often seen in the respiratory tract of smokers
Mechanism: reprogramming of stem cells to differentiate along a new pathway.

Cell Injury

Stress (if severe, prolonged or damaging) leads to injury
Cell injury can be reversible or irreversible
Irreversible cell injury results in cell death, which can be necrosis or apoptosis

Mechanisms of Cell Injury

Depletion of ATP: caused by reduced oxygen and nutrient supply, mitochondrial damage, or toxins
Mitochondrial damage: sensitive to hypoxia, chemical toxins, and radiation; can lead to necrosis or apoptosis
Influx of calcium: increased intracellular calcium can induce apoptosis
Accumulation of oxygen-derived free radicals (oxidative stress)
Defects in membrane permeability: increased permeability leads to loss of osmotic balance, influx of fluids, and loss of cellular contents
Damage to DNA and proteins: can trigger apoptosis if repair mechanisms fail

Cellular Responses and Adaptations to Stress

Cells adapt to surrounding stimuli or changes to survive
Cellular responses include adaptation, injury, intracellular accumulation, and calcification
Adaptation: reversible changes in size, number, phenotype, metabolic activity, or function in response to changes in the environment
Adaption can be physiologic or pathologic

Hypertrophy

An increase in cell size resulting in an increase in the size of the organ
Occurs in nondividing cells (cardiac myocytes, skeletal muscles)
Can coexist with hyperplasia in dividing cells (skin, GI tract cells)
Caused by increased functional demand (workload) or hormonal stimulation
Mechanism: increased production of cellular structural proteins and organelles
Example: left ventricle hypertrophy in the heart

Hyperplasia

An increase in the number of cells resulting in an increased mass of the organ or tissue
Takes place in cells capable of dividing
Mechanism: growth factor-driven proliferation of mature cells, or increased output of new cells from tissue stem cells
Types:
- Physiologic: hormonal (e.g., female breast during puberty and lactation) or compensatory (e.g., partial liver resection)
- Pathologic: excessive hormone stimulation (e.g., endometrial hyperplasia), or infections (e.g., skin warts)
Pathologic hyperplasia can be a fertile soil for development of malignancy.

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Description

Explore the concepts of atrophy and metaplasia in this quiz. Learn about the mechanisms and causes behind these physiological changes, including the types of atrophy and their implications. Test your understanding of cellular adaptations and their significance in pathology.