Cellular Adaptation and Response to Injury
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Questions and Answers

What is the term used to describe the steady state that cells normally maintain?

Homeostasis

What are adaptations in the context of cellular responses to stress?

Adaptations are alterations that enable cells to cope with stresses without damage.

What is the difference between reversible injury and cell death?

Reversible injury refers to structural and functional abnormalities that can be corrected if the injurious agent is removed, while cell death is irreversible and leads to the end result of injury.

In the context of cellular responses to stress and noxious stimuli, what can cells undergo to achieve a new steady state and preserve viability and function?

<p>Cells can undergo adaptation.</p> Signup and view all the answers

What are the stages of progressive impairment following different types of insults?

<p>Adaptation, Reversible injury, Cell death</p> Signup and view all the answers

Adaptations are irreversible changes in the size, number, phenotype, metabolic activity, or functions of cells in response to changes in their environment.

<p>False</p> Signup and view all the answers

Which of the following is NOT a type of cellular adaptation?

<p>Inflammation</p> Signup and view all the answers

What is hypertrophy?

<p>Hypertrophy is an increase in the size of cells that results in an increase in the size of the affected organ.</p> Signup and view all the answers

What is the most common stimulus for hypertrophy of skeletal and cardiac muscle?

<p>Increased workload</p> Signup and view all the answers

Give an example of physiologic hypertrophy.

<p>The massive physiologic growth of the uterus during pregnancy.</p> Signup and view all the answers

What is the role of oestrogenic hormone in uterine hypertrophy during pregnancy?

<p>Oestrogenic hormone signaling through estrogen receptors increases synthesis of smooth muscle proteins and cell size.</p> Signup and view all the answers

How do muscle cells respond in pathologic hypertrophy?

<p>Muscle cells respond by synthesizing more protein and increasing the number of myofilaments per cell.</p> Signup and view all the answers

Cardiac hypertrophy always improves function.

<p>False</p> Signup and view all the answers

What is hyperplasia?

<p>Hyperplasia is an increase in the number of cells in an organ or tissue in response to a stimulus.</p> Signup and view all the answers

Hyperplasia and hypertrophy are always distinct processes.

<p>False</p> Signup and view all the answers

Hyperplasia can occur in any tissue.

<p>False</p> Signup and view all the answers

Give an example of physiologic hyperplasia.

<p>The increase in the size of the breast during pregnancy.</p> Signup and view all the answers

Explain the role of the bone marrow in physiologic hyperplasia.

<p>The bone marrow undergoes rapid hyperplasia in response to a deficiency in mature blood cells, such as in acute bleeding or hemolysis.</p> Signup and view all the answers

What is pathologic hyperplasia?

<p>Pathologic hyperplasia is due to inappropriate or excessive stimulation by hormones and growth factors.</p> Signup and view all the answers

Which of the following is NOT a characteristic of metaplasia?

<p>It is always irreversible.</p> Signup and view all the answers

What is the most common epithelial metaplasia, and where does it occur?

<p>The most common epithelial metaplasia is columnar to squamous, which occurs in the respiratory tract in response to chronic irritation.</p> Signup and view all the answers

What is the common cause of squamous metaplasia in smokers?

<p>Cigarette smoking.</p> Signup and view all the answers

Explain the connection between Vitamin A deficiency and squamous metaplasia.

<p>Vitamin A deficiency can induce squamous metaplasia in the respiratory epithelium and the cornea, with potentially serious consequences for vision.</p> Signup and view all the answers

Describe squamous to columnar metaplasia, and give an example.

<p>Squamous to columnar metaplasia is the replacement of squamous epithelium by columnar epithelium. An example is Barrett esophagus, in which the esophageal squamous epithelium is replaced by intestinal-like columnar cells under the influence of refluxed gastric acid.</p> Signup and view all the answers

What are the causes of atrophy?

<p>Atrophy can be caused by decreased protein synthesis, increased protein breakdown, and can be physiologic or pathologic.</p> Signup and view all the answers

Describe an example of atrophy that occurs during early embryonic development.

<p>In early embryonic development, some embryonic structures such as branchial clefts, thyroglossal ducts, and notochord undergo involution as part of morphogenesis.</p> Signup and view all the answers

What is disuse atrophy?

<p>Disuse atrophy is a reduction in the size of an organ or tissue due to a decrease in workload.</p> Signup and view all the answers

What is denervation atrophy?

<p>Denervation atrophy is atrophy of muscle fibers due to damage to their nerve supply.</p> Signup and view all the answers

Explain the role of the ubiquitin-proteasome pathway in atrophy.

<p>The ubiquitin-proteasome pathway is responsible for the degradation of cellular proteins, and it is activated in atrophy due to nutrient deficiency or disuse.</p> Signup and view all the answers

What is autophagy?

<p>Autophagy is a process in which a cell eats its own contents, delivering cytoplasmic materials to the lysosome for degradation.</p> Signup and view all the answers

Why is autophagy considered a survival mechanism?

<p>Autophagy functions as a survival mechanism under various stress conditions, maintaining the integrity of cells by recycling essential metabolites and clearing intracellular debris.</p> Signup and view all the answers

Describe the function of Atg autophagy-related genes.

<p>Atg genes encode proteins required for the creation of autophagosomes.</p> Signup and view all the answers

Autophagy can only trigger apoptosis.

<p>False</p> Signup and view all the answers

How can autophagy promote cancer growth?

<p>Autophagy can promote cancer growth by providing nutrients and energy to cancer cells, and by removing harmful substances that would normally trigger cell death.</p> Signup and view all the answers

What is the link between impaired autophagosome maturation and neurodegenerative disorders?

<p>Impaired autophagosome maturation is associated with neurodegenerative disorders, such as Alzheimer's disease, as it can lead to the accumulation of misfolded proteins and other harmful substances in neurons.</p> Signup and view all the answers

Give an example of infectious diseases that are degraded by autophagy.

<p>Mycobacteria, Shigella spp., and HSV-1 are examples of pathogens that can be degraded by autophagy.</p> Signup and view all the answers

How are microbial proteins digested and delivered to antigen presentation pathways during autophagy?

<p>During autophagy, microbial proteins are digested and delivered to antigen presentation pathways, allowing the immune system to recognize and mount a response against invading pathogens.</p> Signup and view all the answers

Macrophage-specific deletion of Atg5 has been shown to decrease susceptibility to tuberculosis.

<p>False</p> Signup and view all the answers

What are the two inflammatory bowel diseases linked by genome-wide association studies to SNPs in ATG16L1?

<p>Crohn disease and ulcerative colitis.</p> Signup and view all the answers

Study Notes

Cellular Adaptation

  • Cells maintain homeostasis, a steady state.
  • Adaptations are changes enabling cells to cope with stress without damage.
  • Reversible injury: structural and functional abnormalities corrected if the stressor is removed.
  • Cell death: irreversible injury results in cell death.
  • All diseases begin with molecular or structural changes in cells.
  • Rudolf Virchow is considered the father of modern pathology.
  • Cell stress or injury leads to tissue and organ injury ultimately shaping disease patterns.

Learning Outcomes

  • Understand the stages of cellular response to stress and injury.
  • Correlate injurious stimuli with cellular responses, including;
    • Hyperplasia
    • Hypertrophy
    • Atrophy
    • Metaplasia
  • Describe the role of autophagy.
    • Cellular adaptations include: hyperplasia, hypertrophy, atrophy, and metaplasia.
    • Autophagy is a cellular survival mechanism.
    • It involves breaking down cellular components in lysosomes.
    • It can be involved in disease processes.

Nature of Injurious Stimuli

  • Altered physiology (e.g., increased demand, decreased nutrients, chronic irritation, reduced oxygen).
  • Chemical, microbial infections, & DNA damage.
  • Cumulative sublethal injury over time.
  • Genetic or acquired metabolic alterations play a role.
    • Some examples of injurious stimuli include: increased hormones, increased demand, decreased nutrient, chronic irritation, reduced oxygen supply, chemical injury or microbial infection, and various types of injury (progressive and severe).

Cellular Responses to Stimuli

  • Adaptations
    • Hyperplasia (increase in cell number).
    • Hypertrophy (increase in cell size).
    • Atrophy (decrease in cell size).
    • Metaplasia (change in cell type).
  • Injury
    • Reversible (cell swelling).
    • Irreversible (necrosis, apoptosis).
  • Intracellular accumulations are possible consequences of injury.

Hypertrophy

  • Increased cell size and functioning.
  • Caused by physiologic or pathologic stimuli.
  • Skeletal and cardiac muscle hypertrophy is often due to increased workload.
  • Physiologic hypertrophy
    • Examples: hormonal stimulation during pregnancy. Increased demand such as in body builders.
  • Pathologic hypertrophy
    • Example: heart enlargement due to pressure overload.
  • Mechanisms involve growth factors, direct effects on cell proteins, and signaling pathways (like PI3K/AKT).
  • Also involves other transcription factors such as GATA4, NFAT, and MEF2 involved in increasing muscle protein genes.

Hyperplasia

  • Increase in the number of cells.
  • Adaptive response.
  • Occurs in cells capable of division.
  • Can be physiologic (hormonal) or pathologic (abnormal hormones or growth factors).
    • Example: Bone marrow in response to deficient mature cells.
    • Example: Skin warts caused by papillomaviruses in epithelial tissue.

Metaplasia

  • Reversible change of one cell type to another.
  • Adaptive response to stressors.
    • Example: Smoking replacing columnar cells with squamous cells in the airways to have a protective effect.
  • Predisposes to malignant transformations in some cases.

Atrophy

  • Reduced cell size and number.
  • Caused by decreased protein synthesis or increased protein breakdown.
  • Physiologic:
    • Normal process for organs like thymus during adult life.
  • Pathologic:
    • Disuse atrophy: loss of workload such as a broken bone in a cast.
    • Loss of innervation.
    • Decreased blood supply: from diseases like atherosclerosis.
    • Lack of hormonal stimulation.
  • Mechanism: reduced trophic signals, ubiquitin-proteasome pathway, and increased autophagy.

Autophagy

  • Process where a cell recycles its own components.
  • Cellular survival mechanism to withstand stress, especially nutrient deprivation.
  • Steps: nucleation, isolation membrane formation, autophagosome formation, maturation and fusion with lysosomes, degradation of components.
  • Important in disease contexts and can either contribute to or protect against disease.

Mechanisms of processes

  • Emphasizes the cellular processes supporting each.

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Pathology: Cellular Adaptation Lecture Notes PDF

Description

Explore the fascinating world of cellular adaptations in response to stress and injury. This quiz covers crucial concepts like hyperplasia, hypertrophy, atrophy, metaplasia, and the role of autophagy in maintaining cellular health. Test your understanding of how cells react to harm and the implications for disease development.

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