Homeostasis and Cellular Adaptation
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What is the defining characteristic of homeostasis in a cell?

  • An inflexible state that cannot adapt to environmental variations.
  • A condition where the external environment dictates cellular operation.
  • A state of constant, unchanging conditions.
  • A dynamic equilibrium where the cell maintains a stable internal environment in the face of changing conditions. (correct)
  • Cellular adaptation is best described as which of the following?

  • A temporary condition resulting in permanent cell damage.
  • A process that instantly restores cells to their original condition.
  • An automatic response that always leads to cell death
  • An altered state that aims to preserve cellular viability under stress. (correct)
  • Which cellular adaptation involves an increase in cell size?

  • Hyperplasia
  • Hypertrophy (correct)
  • Metaplasia
  • Atrophy
  • What is the key difference between reversible and irreversible cell injury?

    <p>Irreversible injury culminates in cell death, while reversible injury allows for recovery. (B)</p> Signup and view all the answers

    Which of these cellular events is the first manifestation of almost all forms of cell injury?

    <p>Cellular swelling (B)</p> Signup and view all the answers

    Which process is NOT a cause of reversible cell injury?

    <p>Irreversible membrane defects (C)</p> Signup and view all the answers

    What is the primary outcome of an inability to adapt to cellular stress?

    <p>Cell death (C)</p> Signup and view all the answers

    Which event is considered an irreversible change in cellular injury?

    <p>Mitochondrial irreversibility (C)</p> Signup and view all the answers

    Which of the following best describes myofibrillar hypertrophy?

    <p>Increase in the size of myofibrils (C)</p> Signup and view all the answers

    What is the primary difference between hyperplasia and hypertrophy in muscle tissue?

    <p>Hyperplasia involves an increase in the number of muscle fibers, while hypertrophy involves an increase in the size of existing muscle fibers. (C)</p> Signup and view all the answers

    Which cellular process is NOT typically associated with atrophy?

    <p>Increased cellular proliferation (D)</p> Signup and view all the answers

    Steatosis is characterized by the intracellular accumulation of which substance?

    <p>Lipids (A)</p> Signup and view all the answers

    Which of the following is a characteristic finding of dystrophic calcification?

    <p>Gross appearance of hard, gritty, tan-white lumpy tissue (A)</p> Signup and view all the answers

    Which stain is most useful for visualizing glycogen accumulation in tissues?

    <p>PAS stain (B)</p> Signup and view all the answers

    What is the primary source of hemosiderin?

    <p>Hemoglobin (A)</p> Signup and view all the answers

    What is the key feature of metaplasia?

    <p>A reversible change where one adult cell type is replaced by another. (A)</p> Signup and view all the answers

    Which of the following scenarios is a typical example of metaplasia?

    <p>Gastric mucosa in Meckel diverticulum (D)</p> Signup and view all the answers

    Dysplasia is best characterized as:

    <p>Cells having disordered arrangement that may progress to cancer. (D)</p> Signup and view all the answers

    Which of the following is a key characteristic of cytoplasmic cell death?

    <p>Formation of large vacuoles that sequentially degrade organelles. (C)</p> Signup and view all the answers

    What process is primarily associated with programmed cell death, or apoptosis?

    <p>Activation of an internal suicide program. (B)</p> Signup and view all the answers

    Which of the following best describes the initial morphological changes seen in necrosis?

    <p>Denaturation of proteins followed by enzymatic digestion. (A)</p> Signup and view all the answers

    Extensive damage to which cellular structure is a key event leading to necrosis?

    <p>Plasma membrane. (B)</p> Signup and view all the answers

    What is 'autolysis' within the context of necrosis?

    <p>Digestion of dead cells by their own lysosomal enzymes. (B)</p> Signup and view all the answers

    Which type of necrosis is most commonly associated with denaturation of proteins, while preserving cell framework and is seen in organs such as the heart, kidneys, and liver?

    <p>Coagulation Necrosis. (D)</p> Signup and view all the answers

    What is characteristic of caseous necrosis?

    <p>It appears as soft, friable ‘cheesy’ material. (D)</p> Signup and view all the answers

    Which of the following best describes fat necrosis?

    <p>It involves the action of lipases in adipose tissue, forming chalky white areas. (A)</p> Signup and view all the answers

    What is a hallmark of liquefaction necrosis?

    <p>Fluid-filled cavitation within a tissue. (B)</p> Signup and view all the answers

    How is 'gangrene' best defined?

    <p>Advanced necrosis visible to the naked eye. (A)</p> Signup and view all the answers

    Which cell type is least likely to undergo hyperplasia?

    <p>Neuron. (D)</p> Signup and view all the answers

    What is the defining characteristic of hypertrophy?

    <p>Increase in cell size without change in cell number. (C)</p> Signup and view all the answers

    Which of the following is considered a physiological cause of hyperplasia?

    <p>Breast development during pregnancy. (D)</p> Signup and view all the answers

    What does 'metaplasia' refer to?

    <p>Change in cell differentiation from one cell type to another. (B)</p> Signup and view all the answers

    What does the term 'motogen' refer to?

    <p>A signal that increases cell movement. (D)</p> Signup and view all the answers

    What is the principal outcome when a cell's adaptive capacity is surpassed by excessive stress?

    <p>Irreversible cell injury leading to cell death (B)</p> Signup and view all the answers

    Which cellular response is characterized by a change in cell type while maintaining cell viability?

    <p>Metaplasia (B)</p> Signup and view all the answers

    During cellular injury, which of these changes occur before the cell reaches irreversible damage?

    <p>Increased membrane permeability and cellular swelling (B)</p> Signup and view all the answers

    In the progression from reversible to irreversible cell injury, what is the next stage after cellular swelling?

    <p>Mitochondrial Irreversibility (A)</p> Signup and view all the answers

    Which alteration is NOT directly associated with 'reversible' cellular injury?

    <p>Mitochondrial irreversibility (A)</p> Signup and view all the answers

    Which cellular process is characterized by a cell's ability to adjust to changes in both its internal and external environment?

    <p>Homeostasis (B)</p> Signup and view all the answers

    Which of the following is considered to be a 'Type II cell-death'?

    <p>Autophagic cell death (D)</p> Signup and view all the answers

    Which of the following is not a part of injury mechanism in reversible cellular damage?

    <p>Lysosomal Digestion (B)</p> Signup and view all the answers

    In the context of muscle growth, which scenario best exemplifies myofibrillar hypertrophy?

    <p>An increase in muscle fiber size via increased myofibril size. (A)</p> Signup and view all the answers

    Which of the following correctly pairs a cellular adaptation with a potential consequence?

    <p>Metaplasia: Potential for development into neoplasia. (A)</p> Signup and view all the answers

    A patient's tissue sample shows deeply basophilic deposits with a glassy, amorphous appearance. These are most likely indicative of which process?

    <p>Dystrophic Calcification. (D)</p> Signup and view all the answers

    Which of the following is a key characteristic of lipofuscin?

    <p>It is a finely granular yellow-brown pigment resulting from membrane lipid peroxidation. (C)</p> Signup and view all the answers

    Intracellular accumulation of which substance is best visualized using Prussian blue stain?

    <p>Hemosiderin. (B)</p> Signup and view all the answers

    A patient presents with a tissue sample showing an accumulation of yellow-brown crystalline material within macrophages. Recent history indicates area of hemorrhage. Which pigment is most likely present?

    <p>Hemosiderin (D)</p> Signup and view all the answers

    Which description best differentiates between dystrophic and metastatic calcification?

    <p>Dystrophic calcification arises in damaged tissues under normal serum calcium levels, while metastatic calcification arises in normal tissues secondary to hypercalcemia. (C)</p> Signup and view all the answers

    Following chronic exposure to a respiratory irritant, the ciliated columnar epithelium of the bronchi is replaced with stratified squamous epithelium. Which cellular adaptation best describes this change?

    <p>Metaplasia. (B)</p> Signup and view all the answers

    A researcher observes increased eosinophilic, glassy droplets in the cytoplasm of renal tubule cells. This finding is most indicative of which process?

    <p>Increased reabsorption of protein. (A)</p> Signup and view all the answers

    Which intracellular pigment is specifically derived from hemoglobin and is often seen in areas of recent hemorrhage?

    <p>Hemosiderin. (D)</p> Signup and view all the answers

    Which signaling mechanism involves a cell releasing a peptide that acts on the cell itself intracellularly?

    <p>Intracrine/Metacrine (D)</p> Signup and view all the answers

    A pathologist examines a tissue sample with extensive cellular damage. Which finding would suggest that necrosis is occurring, and not apoptosis?

    <p>Mitochondrial vacuolization and leakage of lysosomal enzymes (D)</p> Signup and view all the answers

    Following a myocardial infarction, a patient's heart tissue shows areas of cell death where the cellular outlines remain visible, and the tissue appears firm before becoming soft. This is an example of which type of necrosis?

    <p>Coagulation necrosis (D)</p> Signup and view all the answers

    In a tissue sample from a patient with tuberculosis, a soft, cheese-like material is observed. This is characteristic of which type of necrosis?

    <p>Caseous necrosis (C)</p> Signup and view all the answers

    A patient has suffered trauma to the abdomen, resulting in damage to adipose tissue. Lipases act on the damaged fat cells, and calcium deposits form, creating chalky white areas. What type of necrosis?

    <p>Fat necrosis (A)</p> Signup and view all the answers

    In the context of gangrene, what is the crucial differentiating factor between 'dry' and 'wet' gangrene?

    <p>The predominant type of necrosis and presence of bacterial overgrowth (C)</p> Signup and view all the answers

    Which of the following cell types is typically incapable of undergoing hyperplasia due to their static nature?

    <p>Skeletal Muscle Cells (C)</p> Signup and view all the answers

    A patient with a goiter, due to low iodine intake, experiences an increase in thyroid gland size. What cellular mechanism contributes to the enlargement seen?

    <p>Hyperplasia and hypertrophy (B)</p> Signup and view all the answers

    Following a partial hepatectomy, the remaining portion of the liver regenerates. This is an example of which type of hyperplasia?

    <p>Physiological-compensatory (B)</p> Signup and view all the answers

    In a patient with a myocardial infarction, the heart muscle does not increase in cell number but does exhibit an increased size. Which adaptation does this describe?

    <p>Hypertrophy (C)</p> Signup and view all the answers

    A researcher is studying a cell that demonstrates increased cell size without an increase in cell number. What is the best description of this phenomenon?

    <p>The cell is undergoing hypertrophy (C)</p> Signup and view all the answers

    Which of the following is a function of the signaling molecule HGF? (Hepatocyte growth factor)

    <p>Promoting cell proliferation, cell movement and changes in cell shape (B)</p> Signup and view all the answers

    A patient is diagnosed with a benign prostatic hyperplasia (BPH). What cellular adaptation primarily contributes to the enlargement of the prostate gland?

    <p>Hyperplasia of glandular epithelial cells (D)</p> Signup and view all the answers

    Which growth factor plays a significant role in angiogenesis?

    <p>Vascular Endothelial Growth Factor (VEGF) (D)</p> Signup and view all the answers

    In a case of a keloid, where there is excessive scarring, the increased synthesis of extracellular matrix components is associated with which mediator?

    <p>Transforming Growth Factor β (TGFβ) (D)</p> Signup and view all the answers

    Study Notes

    Homeostasis and Cellular Adaptation

    • Homeostasis is a state of balance within the body's organs, tissues, and cells where the body's physiologic and metabolic capabilities adapt to internal and external environmental changes. A normal cell is in a steady state, able to handle physiologic demands based on its adaptive capacity.
    • Cellular adaptation occurs when cells are exposed to excessive physiological stresses or pathological stimuli, resulting in an altered state that preserves cell viability.
    • Adaptations allow cells to conform to environmental changes to adjust and accommodate internal and external stimuli. Cells possess inherent plasticity to survive, adapting to environmental pressures.

    Cellular Responses to Stress

    • Cellular responses to stress can include:
      • Hypertrophy: Increase in cell size
      • Hyperplasia: Increase in cell number
      • Atrophy: Reduction in cell size
      • Metaplasia: Change in the type of a cell
      • Dysplasia: Abnormal hyperplasia, potentially a precursor to cancer
      • Intracellular accumulations (e.g., water, proteins, fats, calcifications)
      • Cellular degeneration (damage to cellular components)

    Cell Injury and Death

    • If adaptation limits are exceeded, cell injury occurs, leading to cell death.
    • Cell death can manifest in these ways:
      • Necrosis: Premature cell death, various types (coagulative, liquefactive, caseous, fat, gangrenous)
      • Apoptosis: Programmed cell death (a natural process, type I)
      • Autophagy (type II): Cellular self-digestion and repair
      • Mitotic catastrophe (type of cell death)

    Injury Mechanisms and Cell Death

    • Injury causes (reversible): Hypoxia (low oxygen), physical agents, chemical agents, infectious agents, immunologic factors, genetic factors, and nutritional factors
    • Injury mechanisms (reversible): Decreased oxidative phosphorylation, ATP depletion, cellular swelling, increased intracellular calcium, increased free radicals, increased cell membrane permeability
    • A continuum exists from reversible changes to irreversible changes to cellular death.

    Morphological Changes and Cell Death

    • Cellular swelling is an initial hallmark of most cell injuries.
    • Cellular death involves irreversible mitochondrial dysfunction and profound membrane disturbances.

    Types of Cell Death

    • Necrosis (type III): Cellular damage, often due to infection or trauma
    • Apoptosis (programmed cell death): A regulated, essential type of cell death.
    • Autophagic cell death: Cellular self-digestion, a sort of repair process.

    Necrosis

    • Necrosis is the collection of morphologic changes following cell death in living tissue or organs.
    • Key processes include protein denaturation and enzymatic breakdown of organelles.
    • Causes that can trigger necrosis: mitochondrial vacuolization, extensive plasma membrane damage, lysosomal swelling, leakage of cytoplasmic/lysosomal enzymes, and activation of certain enzymes within the cell.
    • Outcomes of necrosis include autolysis (digestion by the cell's own enzymes) and heterolysis (digestion by enzymes from immune cells).

    Types of Necrosis

    • Coagulative, Liquefactive, Caseous, Fat, and Gangrenous necrosis.

    Examples of Tissue Necrosis

    • Coagulative: Kidney, heart, liver tissue
    • Liquefactive: Brain tissue (e.g., brain stroke), liver abscess
    • Caseous: Tuberculosis lesions
    • Fat: Adipose tissue
    • Gangrenous: Advanced necrosis, often visible (dry or wet)

    Cellular Adaptation Examples

    • Hyperplasia: Increased cell number in response to physiological or pathological stimuli (e.g., breast during pregnancy, liver after partial resection, psoriasis, goiter)
    • Hypertrophy: Increased cell size (e.g., heart muscle in response to hypertension)

    Atrophy

    • Atrophy is the decrease in cell size, organelles, protein synthesis (macromolecules), often associated with increased protein degradation. Types include reduction in cell size and/or decreased cell number; hypoplasia represents reduced proliferation and increased loss. Examples include Alzheimer's disease and reduced skeletal muscle in disuse atrophy.

    Cellular Accumulations

    • Lipid accumulation (e.g., steatosis in the liver)
    • Protein accumulation (e.g., certain genetic disorders, alpha-1-AT deficiency)
    • Glycogen storage disorders
    • Pigments (exogenous/endogenous)
      • Exogenous: Carbon, Tattoos
      • Endogenous: Lipofuscin (wear and tear pigment), Melanin, Hemosiderin (iron)
    • Calcification (Dystrophic or metastatic)

    Cellular Signaling

    • Cells communicate and respond to internal and external signals (hormones, growth factors, etc.) affecting cell number and size. Signals can include: Mitogens, Morphogens, and Motogens.

    Growth Factors

    • Growth factors (GFs) are substances that stimulate cell growth. They often have receptors on cell surfaces and within cells, exerting various functions and potentially being oncogenic.

    Cellular Metaplasia and Dysplasia

    • Metaplasia: A reversible change in one cell type to another (e.g., lung cells in smokers, gastric mucosa in Meckel diverticulum, oesophagitis)
    • Dysplasia: Abnormal development and potentially pre-cancerous cellular changes (e.g., Cervical dysplasia). Dysplasia can progress to malignant neoplasms.

    Cellular Division and Non-Division

    • Some cells divide continuously (stem cells, some epithelial cells)
    • Some cells divide conditionally (liver, some epithelial)
    • Some cells do not divide (neurons, skeletal muscle, cardiac muscle)

    Cell Proliferation - Examples

    • Physiological: Breast (during puberty, pregnancy, lactation), Uterus (during pregnancy), Kidney (after nephrectomy), Liver (after partial hepatectomy)
    • Pathological: Psoriasis, Goiter, Benign Prostatic Hyperplasia (BPH), Endemic Goiter (low iodine)
    • Non-dividing cells: neurons, skeletal and cardiac muscle

    Hypertrophy

    • Hypertrophy involves no change in cell number; a reversible increase in cell size, and it is common in non-dividing cells (myocardium, skeletal muscle, neurons).
    • Key changes in hypertrophy include increased DNA, RNA, and protein; increased synthesis; and reduced loss.
    • Hypertrophy pathways include satellite cell recruitment, myonuclear domain size increases, and, less commonly, hyperplasia (increased muscle numbers).
    • Sarcoplasmic or myofibrillar hypertrophy occurs, increasing glycogen or myofibril sizes, respectively.
    • Scarring or keloid formation is associated with excess TGFβ overexpression and fibroblast polyclonality.

    Atrophy

    • Atrophy involves a decrease in cell size, organelles, synthesis of macromolecules, and often increased protein degradation.
    • There are reductions in cell size and/or cell numbers, and hypoplasia is represented by decreased proliferation and increased loss. Examples include Alzheimer's Disease and disuse atrophy.

    Cellular Accumulations (Continued)

    • Lipids: Steatosis (fatty change) is the accumulation of lipids within hepatocytes, potentially due to ethanol, drugs, or toxins. Accumulation can occur at any step from fatty acid entry into the cell to triglyceride removal. Cholesterol accumulation may be observed as needle-like clefts in tissues or in macrophages as "foamy macrophages".
    • Proteins: Accumulation may be due to impaired metabolism, increased reabsorption in renal tubules, defective protein folding, or other factors. This can lead to toxicity in some neurodegenerative diseases.
    • Glycogen: Glycogen accumulation can be normal or pathological (glycogen storage diseases).
    • Pigments: Exogenous pigments (e.g., carbon, tattoos) and endogenous pigments (e.g., lipofuscin, melanin, hemosiderin).
    • Calcifications: Dystrophic calcifications occur in nonviable tissue with normal serum calcium levels. Metastatic calcifications occur in normal viable tissues due to hypercalcemia.

    Types of Necrosis (Continued)

    • Coagulative necrosis: Characterized by denaturation of cytoplasmic proteins, preserving the cell's basic shape. Common in heart, kidneys, and liver.
    • Caseous necrosis: Characteristic of tuberculous lesions, appears as a soft, friable, "cheesy" material.
    • Fat necrosis: Necrosis in adipose tissue induced by lipases, generating chalky white areas (fat saponification).
    • Liquefaction necrosis: Occurs primarily in the brain and other areas with high numbers of macrophages. In the brain, liquefication necrosis is a characteristic late-phase change observed in stroke.
    • Gangrene: Advanced necrosis visible macroscopically, can be dry or wet (based on whether the necrosis is coagulative or liquefactive, respectively).

    Metaplasia and Dysplasia

    • Metaplasia: A reversible change where one mature adult cell type is replaced by another. This often occurs in response to abnormal environmental stimuli to better withstand the altered environment. This could occur in specialized tissues such as the esophagus or lungs. Loss of function or complications due to metaplastic functioning can occur.
    • Dysplasia: Dysplasia can be a cellular precursor to cancer, exhibiting abnormal changes in cell numbers/size and cellular arrangement.

    Cellular Signaling

    • Hormone action: Hormones bind to receptors, which triggers a cascade of intracellular signaling pathways leading to transcription and cellular responses.
    • Growth factors: Growth factors (GFs) stimulate cell growth, often with multiple receptors and multiple functions. GFs can be mitogenic, motogenic, morphogenic, and potentially oncogenic. Examples include: HGF, c-Met, EGF, c-erbB1, FGFs, VEGF, and TGFβs.

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    Description

    This quiz explores the concepts of homeostasis and how cells adapt to stress. It covers various cellular responses to stress, including hypertrophy, hyperplasia, and metaplasia. Additionally, the quiz examines cell injury and death mechanisms, providing a comprehensive understanding of cellular resilience and health.

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