Tissue Regeneration and Repair

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Questions and Answers

What is the primary characteristic of healing by primary intention compared to secondary intention?

  • It has a higher risk of infection.
  • It involves extensive granulation tissue.
  • It primarily repairs the epithelial layer. (correct)
  • It produces a larger scar.

Which factor is least likely to decrease the effectiveness of tissue repair?

  • Infection
  • Nutritional deficiencies
  • Adequate blood supply (correct)
  • Mechanical stress

What is a potential consequence of excessive tissue repair during wound healing?

  • Reduced inflammation
  • Improved tissue tensile strength
  • Rapid epithelial regeneration
  • Keloid formation (correct)

What is the primary outcome of wound healing by secondary intention?

<p>Significant contraction and extensive granulation tissue. (D)</p> Signup and view all the answers

Which scenario would likely lead to wound dehiscence?

<p>Pressure from external sources on the wound site. (D)</p> Signup and view all the answers

What is the primary distinction between regeneration and connective tissue deposition in the repair process?

<p>Regeneration replaces lost tissue, while connective tissue deposition forms fibrous tissues to bridge gaps. (B)</p> Signup and view all the answers

Which of the following components is NOT a direct part of connective tissue?

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

What is fibrous connective tissue primarily responsible for in the healing process?

<p>Restoring damaged or lost tissue architecture when regeneration fails (B)</p> Signup and view all the answers

Which of the following accurately describes a structural feature of the extracellular matrix (ECM)?

<p>It is made up of collagen, ground substance, and a basement membrane. (D)</p> Signup and view all the answers

Which of the following statements about cutaneous wound healing is most accurate?

<p>It involves both regeneration of epithelial cells and the formation of scar tissue. (B)</p> Signup and view all the answers

In the context of regeneration after an injury, which type of cells are primarily responsible for creating the extracellular matrix?

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

What term is often used to describe connective tissue due to its supportive role?

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

Which of the following best describes the role of fibroblasts in tissue repair?

<p>Produce collagen and other extracellular matrix material (D)</p> Signup and view all the answers

What characteristic distinguishes labile tissue from stable and permanent tissues?

<p>Highly proliferative and continuously renewing (B)</p> Signup and view all the answers

During the cell cycle, which phase is considered the resting phase?

<p>G0 (C)</p> Signup and view all the answers

What happens to permanent tissues when they experience injury?

<p>They undergo fibrosis leading to scarring (C)</p> Signup and view all the answers

Which statement about liver regeneration is correct?

<p>The liver has a unique ability to regenerate after resection due to specific cellular mechanisms (B)</p> Signup and view all the answers

What process initiates the inflammatory phase of tissue repair?

<p>Removal of damaged tissue and debris (C)</p> Signup and view all the answers

Which cell type is primarily responsible for creating granulation tissue?

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

What is the primary factor that limits the regenerative capacity of stable tissue?

<p>Permanent presence in the G0 phase (C)</p> Signup and view all the answers

Which phase of tissue repair involves the breakdown and remodeling of scar tissue?

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

Flashcards

Regeneration (repair)

Replacement of damaged tissue using surviving cells.

Connective Tissue Deposition

Repair method using scar tissue when regeneration fails.

Connective Tissue

Tissue providing structure, strength, and support to other tissues.

Extracellular Matrix (ECM)

Fibrous proteins (like collagen) and ground substance in connective tissue.

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Fibroblasts

Cells responsible for making the Extracellular Matrix.

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Cutaneous Wound Healing

Repair process specific to skin.

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Tissue Repair

Restoration of tissue architecture and function after injury.

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Primary Intention Wound Healing

The healing of a clean, uninfected wound with well-approximated edges, like a sutured surgical incision. Epithelial regeneration predominates.

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Secondary Intention Wound Healing

Healing of a large, infected, or chronic wound. Fibrosis predominates, larger scab, more inflammatory response, and intense granulation tissue formation and wound contraction.

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Wound Dehiscence

Separation of the edges of a surgical wound. Occurs due to inadequate wound healing, often related to infection or mechanical forces such as excessive pressure or torsion.

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Wound Strength

Healed skin is never as strong as original tissue. Early healing shows low strength, increasing gradually to about 70-80% of normal strength by several months post-injury.

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Keloid Scar

A raised scar that grows beyond the boundaries of the original wound.

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Labile Tissues

Tissues with high regeneration capacity; cells continuously divide, never resting.

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Stable Tissues

Tissues with limited regeneration; cells usually rest (G0) but can divide after injury.

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Permanent Tissues

Tissues incapable of regeneration; cell division is impossible after injury.

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Liver Regeneration

Liver's exceptional ability to regenerate, even after significant resection (removal).

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Proliferative Capacity

A tissue’s ability to repair itself, related to cell cycle stages.

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Scar Formation

Repair process where connective tissue replaces damaged or dead cells.

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Regeneration

The process of producing new cells to replace damaged or lost ones.

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Collagen

Main protein in connective tissues. Its excess deposition is called fibrosis/scar.

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Fibrosis

The deposition of excessive connective tissue.

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Study Notes

Tissue Regeneration and Repair

  • Tissue Repair: Restoration of tissue architecture and function post-injury, occurring through regeneration or connective tissue deposition.
  • Regeneration: Proliferation of surviving cells to replace damaged tissue.
  • Connective Tissue Deposition: Laying down fibrous connective tissue to replace damaged tissue when regeneration isn't sufficient. This results in fibrosis or scar formation.
  • Connective Tissue: Provides structure, strength, and support. It's made of ECM (extracellular matrix - collagen, ground substance, basement membrane), stromal cells (like fibroblasts), and vessels/nerves.
  • Tissue Proliferative Capacity: Ability of tissue to repair itself, varies amongst tissues. This depends on the part of the cell cycle cells predominantly reside in.

Tissue Types and Regeneration Capacity

  • Labile Tissues: High regeneration capacity, continuously dividing. Examples: gastrointestinal epithelium, skin, oral mucosa, bone marrow.
  • Stable Tissues: Limited regeneration capacity, cells are normally resting (G0). Examples: connective tissue (fibroblasts, smooth muscle), most solid organs (kidney, pancreas, adrenal glands, lung; liver is a notable exception).
  • Permanent Tissues: No regeneration capacity; cells are always in G0. Examples: neurons, cardiac muscle.

Liver Regeneration

  • Exceptional regeneration capacity: can regenerate after significant resection (up to 90% removal).
  • Two major mechanisms:
    • Priming Phase: Kupffer cells release cytokines (e.g., IL-6) to prepare hepatocytes for growth factors.
    • Proliferation Phase: Growth factors (e.g., HGF, TGF-α) stimulate hepatocyte entry into the cell cycle. However, significant damage to supporting structures can still result in scar tissue formation.

Wound Healing - Cutaneous Wound Healing

  • Types of wound healing:
    • Primary Intention: Clean, uninfected wounds; minimal scar formation and epithelial regeneration predominates.
    • Secondary Intention: Larger, infected or chronic wounds; more scar tissue formation and significant granulation tissue.
    • Tertiary Intention: Delayed primary closure (closure 4-5 days later); similar to secondary but with some primary characteristics.
  • Wound Healing Stages: Inflammatory, proliferative, and remodeling phases.

Wound Healing - General Steps

  • Inflammatory Phase (within 24 hours): Removing debris, secreting cytokines and growth factors.
  • Proliferative Phase (3-5 days): New blood vessel formation (angiogenesis), fibroblast proliferation (scar tissue), granulation tissue production. Granulation tissue is immature connective tissue.
  • Remodeling Phase: Scar tissue remodeling; matrix metalloproteinases degrade ECM.

Pathological Aspects of Wound Healing

  • Inadequate Repair: Wound dehiscence, ulcers (venous, arterial, diabetic, pressure).
  • Excessive Repair: Hypertrophic scar, keloid scar, "proud flesh," wound contractures, desmoid tumors.

Factors Affecting Tissue Repair

  • Infection
  • Foreign bodies
  • Nutrition (Vitamin C deficiency)
  • Medications (glucocorticoids)
  • Blood supply
  • Mechanical factors (pressure)
  • Diseases (diabetes)
  • Injury severity and type
  • Tissue type

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