Tissue Healing and ECM Role
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Questions and Answers

Which of the following is a characteristic of healing by second intention, compared to healing by first intention?

  • More intense inflammatory reaction (correct)
  • Reduced inflammatory response
  • Minimal granulation tissue formation
  • Smaller clot formation

    • In secondary intention healing, what is the primary role of myofibroblasts?

  • Inhibiting the formation of granulation tissue
  • Promoting rapid epithelialization across the wound surface
  • Facilitating wound contraction to reduce the size of the defect (correct)
  • Secreting large amounts of collagen to form a dense scar

    • Which component is predominantly found in the initial clot or scab formed during secondary intention healing?

  • Keratin and melanin
  • Collagen and elastin
  • Fibrin and fibronectin (correct)
  • Hyaluronic acid and proteoglycans

    • Why do larger tissue defects have a greater potential for inflammation-mediated injury during secondary intention healing?

    <p>Greater volume of necrotic debris, exudate, and fibrin (D)</p> Signup and view all the answers

    What is the typical outcome regarding scar tissue formation in secondary intention healing compared to primary intention healing?

    <p>A greater mass of scar tissue (D)</p> Signup and view all the answers

    How do G protein-coupled receptors (GPCRs) typically influence growth factor-related pathways?

    <p>Through the activation of intracellular signaling pathways via G proteins. (A)</p> Signup and view all the answers

    Which of the following is a characteristic of growth factor receptors that lack intrinsic kinase activity?

    <p>They rely on non-receptor kinases to transmit signals downstream. (A)</p> Signup and view all the answers

    What is the role of the extracellular matrix (ECM) in tissue repair?

    <p>It regulates cell proliferation, movement, and differentiation, and serves as a reservoir for growth factors. (B)</p> Signup and view all the answers

    What happens if the ECM is damaged during tissue repair?

    <p>Repair is accomplished via scar formation. (A)</p> Signup and view all the answers

    Which of these represents a function of the ECM?

    <p>Mechanical support to tissues (B)</p> Signup and view all the answers

    How do proteoglycans in the ECM influence cell proliferation and differentiation?

    <p>By binding and displaying growth factors at high concentrations. (A)</p> Signup and view all the answers

    What is the role of fibronectin and laminin in stimulating cells within the ECM?

    <p>They stimulate cells through cellular integrin receptors. (C)</p> Signup and view all the answers

    What role does the extracellular matrix play in maintaining tissue structure and function?

    <p>It regulates cell proliferation, differentiation, and provides mechanical support. (A)</p> Signup and view all the answers

    What is the primary distinction between tissue regeneration and scar formation in tissue repair?

    <p>Tissue regeneration restores original tissue structure and function, whereas scar formation replaces damaged tissue with connective tissue. (A)</p> Signup and view all the answers

    Which factor directly influences the ability of tissues to repair themselves?

    <p>The tissue's intrinsic proliferative capacity. (B)</p> Signup and view all the answers

    What are Induced Pluripotent Stem Cells (iPS) derived from?

    <p>Mature cells through the introduction of specific genes. (C)</p> Signup and view all the answers

    What is a major function of growth factors in tissue repair?

    <p>Stimulating survival, proliferation, migration, and differentiation of cells. (B)</p> Signup and view all the answers

    What activity is intrinsic to Receptor Tyrosine Kinases (RTKs)?

    <p>Phosphorylating tyrosine residues. (C)</p> Signup and view all the answers

    Which of the following best describes autophosphorylation of Receptor Tyrosine Kinases (RTKs)?

    <p>The receptor phosphorylates itself, creating docking sites for signaling molecules. (A)</p> Signup and view all the answers

    Which cells commonly produce growth factors involved in tissue repair?

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

    What is the potential consequence of mutations in proto-oncogenes, which are influenced by growth factors?

    <p>Increased risk of cancer. (C)</p> Signup and view all the answers

    Scar formation occurs when tissue injury is:

    <p>Severe or chronic, damaging parenchymal cells, epithelia, and connective tissue. (B)</p> Signup and view all the answers

    Which factor, if deficient, would most significantly inhibit collagen synthesis and retard wound healing?

    <p>Protein and Vitamin C (D)</p> Signup and view all the answers

    How do glucocorticoids affect scar formation?

    <p>They result in weaker scars by inhibiting growth factor production. (B)</p> Signup and view all the answers

    In the first week after injury during cutaneous wound healing by first intention, what cellular event occurs around day 3?

    <p>Macrophages replace neutrophils, and granulation tissue invades the incision space. (D)</p> Signup and view all the answers

    What is the primary characteristic of the scar at the end of the first month of healing by first intention?

    <p>A cellular connective tissue, largely devoid of inflammatory cells, covered by a normal epidermis. (D)</p> Signup and view all the answers

    Following an injury, which event would most likely lead to healing via scar formation rather than complete tissue restoration?

    <p>A deep laceration through the dermis, involving damage to non-dividing cells. (D)</p> Signup and view all the answers

    Which of the following factors would least likely impair the healing process of a cutaneous wound?

    <p>Adequate perfusion ensuring sufficient oxygen and nutrient supply. (A)</p> Signup and view all the answers

    What is the predominant event during the second week of cutaneous wound healing by first intention?

    <p>Continued collagen accumulation and fibroblast proliferation within the incisional space. (B)</p> Signup and view all the answers

    Flashcards

    Wound Healing

    The process by which the body repairs damaged tissue after an injury.

    Tissue Repair Types

    Two main types: regeneration of injured tissue and scar formation via connective tissue.

    Cell Proliferation

    The process of cell growth and division, essential for tissue regeneration.

    Growth Factors

    Proteins that regulate cell survival, proliferation, and differentiation during tissue repair.

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    Induced Pluripotent Stem Cells (iPS)

    Mature cells reprogrammed to behave like stem cells, capable of differentiating into various cell types.

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    Receptor Tyrosine Kinases (RTKs)

    A class of cell surface receptors with intrinsic kinase activity that phosphorylates tyrosine residues.

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    Angiogenesis

    The formation of new blood vessels from existing ones, a critical process during healing.

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    Scar Formation

    The process of fibrous tissue deposition that replaces normal tissue after injury.

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    Healing by Second Intention

    A complex healing process for large wounds involving regeneration and scarring.

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    Granulation Tissue

    New connective tissue and tiny blood vessels that form during healing.

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    Myofibroblasts

    Cells that aid in wound contraction, acting like muscle cells.

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    Wound Contraction

    The process of a wound shrinking in size, mainly due to myofibroblasts.

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    Secondary Wound Healing

    Healing process involving a larger clot and intense inflammation due to extensive tissue loss.

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    G Protein-Coupled Receptors (GPCRs)

    Cell surface receptors that transmit signals through G proteins.

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    Intrinsic Kinase Activity

    The ability of some receptors to directly perform phosphorylation.

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    Transforming Growth Factor-beta (TGF-β) Receptor

    A receptor that recruits non-receptor kinases for signaling.

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    Extracellular Matrix (ECM)

    A network of proteins surrounding cells, aiding in tissue structure and repair.

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    ECM Remodeling

    The ongoing process of ECM synthesis and degradation.

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    Mechanical Support of ECM

    Collagen and elastin provide structural integrity to tissues.

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    Substrate for Cell Growth

    ECM serves as a surface for cells to attach and proliferate.

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    Role of Fibronectin and Laminin

    These proteins stimulate cells via integrin receptors.

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    Factors Influencing Wound Healing

    Elements that can affect the rate and success of healing, like infection or nutrition.

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    Infection and Healing

    Infection can delay the healing process and prolong inflammation due to immune response.

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    Nutrition's Role in Healing

    Deficiencies in protein and Vitamin C can inhibit collagen synthesis and slow healing.

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    Glucocorticoids Effect

    These can weaken scars by inhibiting growth factors; however, they may help with corneal infections.

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    Mechanical Variables

    Physical factors like pressure that can impair the healing process.

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    Healing by First Intention

    A type of wound healing characterized by minimal tissue loss and rapid repair.

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    Timeline of First Intention Healing

    Healing progresses over weeks: inflammation, granulation, and scar formation occur in stages.

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    Keloid Formation

    An aberration of cell growth leading to excessive scar tissue development beyond the original injury site.

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    Study Notes

    Wound Healing and Tissue Repair

    • Wound healing involves two main reactions: regeneration of injured tissue and scar formation by connective tissue deposition.
    • Lecture objectives include describing cell and tissue regeneration, the repair process using connective tissue, angiogenesis and scar formation, and the mechanism of cutaneous wound healing.

    Tissue Repair

    • Tissue repair occurs through two main reactions: regeneration of the injured tissue and scar formation via connective tissue deposition.
    • Tissue repair reactions vary based on injury severity. Mild injury demonstrates regeneration, while severe injury exhibits scar formation.

    Cell and Tissue Regeneration

    • Injured cell and tissue regeneration involves cell proliferation driven by growth factors. The process is greatly dependent on the integrity of the extracellular matrix.
    • This process includes proliferation, differentiation and the role of stem cells.

    Proliferative Capacities of Tissues

    • Tissues are categorized as labile, stable, or permanent based on their ability to regenerate.
    • Labile cells continuously divide (bone marrow, certain epithelium, skin).
    • Stable cells are quiescent but can divide (liver, kidney, fibroblasts).
    • Permanent cells do not divide (neurons, cardiac myocytes).

    Stem Cells (Embryonic and Adult)

    • Embryonic stem cells are pluripotent, capable of differentiating into any cell type.
    • Adult stem cells are multipotent, able to differentiate into a limited range of cell types. Different types of adult stem cells exist (neural, mesenchymal, hematopoietic, muscle stem cells, epidermal/hair follicle).
    • Induced pluripotent stem cells (iPS) are derived from mature cells by introducing genes from embryonic stem cells.

    Growth Factors

    • Growth factors are mostly proteins that stimulate cell survival, proliferation, migration, differentiation, angiogenesis, and fibrogenesis.
    • Growth factors are crucial for repair processes, stimulating the function of growth control genes.
    • Many growth factors involved in repair are produced by macrophages and lymphocytes, or parenchymal/stromal cells in response to injury. Specific examples given in a table.

    Growth Factor Signaling

    • Growth factor signaling can be categorized based on receptor types with or without intrinsic kinase activity.
    • Receptor Tyrosine Kinases (RTKs) have intrinsic kinase activity, phosphorylating tyrosine residues to activate signaling pathways. Examples include EGFR and insulin receptor.
    • G-Protein-Coupled Receptors (GPCRs) activate intracellular signaling pathways through G-proteins and indirectly influence pathways like cAMP, IP3. Examples include epinephrine and chemokine receptors.
    • Some receptors (e.g., TGF-β receptor) lack kinase activity, relying on associated kinases for signaling.

    Role of the Extracellular Matrix (ECM) in Tissue Repair

    • The ECM is a complex protein network surrounding cells, providing structural support, turgor pressure, and a reservoir for growth factors.
    • ECM is comprised of interstitial matrix and basement membrane, each with distinct components like collagen, fibronectin, elastin, proteoglycans, and hyaluronate.
    • ECM regulates cell proliferation, movement, and differentiation, and plays a role in tissue regeneration and repair.
    • ECM is constantly undergoing synthesis and degradation, which is critical in morphogenesis, wound healing, chronic fibrosis, and tumor invasion.

    Important Functions of ECM

    • Provides mechanical support
    • Acts as a substrate
    • Regulates cell proliferation and differentiation
    • Allows regeneration if intact
    • Supports repair with scar formation if damaged

    Scar Formation

    • Tissues can be repaired by regeneration (complete) or replacement with connective tissue (scar).
    • Scar formation occurs when tissue injury is severe, prolonged, or damages parenchymal, epithelial, and connective tissue causing non-dividing cell harm.
    • It involves angiogenesis, fibroblast migration and proliferation, collagen synthesis, and connective tissue remodeling that culminates in granulation tissue formation. Multiple growth factors are essential for scar formation.

    Steps in Scar Formation

    • A series of steps leads to scar formation: inflammation, formation of new blood vessels, formation of granulation tissues (migration of fibroblasts + deposition of connective tissues, interspersed leukocytes), and scar formation (maturation and reorganization of fibrous tissue).

    Factors Influencing Wound Healing

    • Infection, nutrition, mechanical factors (perfusion, type and extent of injury), and cell growth abnormalities (keloids) affect wound healing.

    Clinical Examples of Tissue Repair (Cutaneous wound healing, Fibrosis)

    • Cutaneous wound healing exemplifies the principles of tissue repair, involving epithelial regeneration and connective tissue scar formation.
    • Healing follows different pathways (first and second intention) dependent on injury severity.

    Healing by First Intention

    • Healing by first intention describes rapid wound healing with minimal tissue loss, primarily epithelial regeneration and formation of a thin scar. It involves a series of cellular events including neutrophil migration, epithelial cell proliferation, macrophage activity and neovascularization.

    Healing by Second Intention

    • Healing by secondary intention involves a greater degree of tissue loss and the formation of prominent, thick scar tissue, requiring extensive ECM deposition, wound contraction from myofibroblasts. It is a more complex and prolonged repair process than healing by first intention.

    Differences between Primary and Secondary Healing

    • Differences in clot formation, inflammation intensity, granulation tissue volume, scar tissue mass, and wound contraction distinguish secondary from primary healing.

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    Related Documents

    Wound Healing and Regeneration (Tissue Repair) PDF

    Description

    Explore the mechanisms of tissue healing through this quiz focused on second intention healing, myofibroblasts, and the extracellular matrix (ECM). Learn about the implications of injury size and the role of growth factor receptors in repair processes. Perfect for students studying advanced biology or pathology.

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