Tissue Repair and Wound Healing Processes

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Questions and Answers

What is the primary role of fibroblasts in the process of fibrosis?

Secretion of inflammatory cytokines

Formation of new endothelial cells

Remodeling the extracellular matrix

Migration and proliferation into injured tissue (correct)

Which growth factor is primarily secreted by macrophages during the proliferative phase of fibrosis?

Vascular Endothelial Growth Factor (VEGF)

Epidermal Growth Factor (EGF)

Transforming Growth Factor-beta (TGF-beta) (correct)

Fibroblast Growth Factor (FGF)

What are the initial processes involved in tissue repair by fibrosis?

Scar formation and local tissue inflammation

Deposition of collagen and ECM remodeling

Migration of macrophages and endothelial cells

Formation of new blood vessels and fibroblast proliferation (correct)

What is the main function of angioblasts in the context of angiogenesis?

To act as precursors for several vascular cell types Signup and view all the answers

What is the final phase of fibrosis that involves reshaping the extracellular matrix?

Connective tissue remodeling Signup and view all the answers

Which factor primarily influences the scar formation phase in tissue repair by fibrosis?

Fibroblast activity level Signup and view all the answers

What is the role of angiogenesis in the repair of injured tissues?

To provide nutrients and oxygen to healing tissues Signup and view all the answers

Which of the following best describes the role of local factors in wound healing?

They influence the speed and efficiency of healing. Signup and view all the answers

What distinguishes the process of fibrosis from normal tissue regeneration?

Fibrosis results in permanent structural changes. Signup and view all the answers

What characterizes the late response in wound healing after 4 weeks?

Mature collagen predominates with decreased vessel density Signup and view all the answers

Which statement is true regarding fibroblast activity during the deposition of the extracellular matrix?

Fibroblasts synthesize collagen starting 3-7 days post-injury. Signup and view all the answers

What is the primary goal of suturing wounds during healing?

Minimize the size of the defect to be filled by granulation tissue Signup and view all the answers

Which phase of wound healing follows inflammation and involves re-epithelialization?

Proliferation Phase Signup and view all the answers

In the context of wound healing by secondary intention, which characteristic is most accurate?

Requires a pool of granulation tissue and exhibits wound contraction Signup and view all the answers

What is the role of growth factors in tissue and organ regeneration?

They stimulate both ECM synthesis and cell replication. Signup and view all the answers

What is the primary difference between primary and secondary union in wound healing?

Primary union requires less granulation tissue than secondary union. Signup and view all the answers

Which aspect is NOT a feature of the maturation phase of wound healing?

Vascularity is at its peak Signup and view all the answers

What accurately describes granulation tissue during the early response phase of wound healing?

Vascularity is significantly high with proliferating capillaries. Signup and view all the answers

The balance between extracellular matrix synthesis and degradation is critically maintained during which phase of healing?

Maturation and Remodeling Phase Signup and view all the answers

Which collagen type is primarily involved during the inflammation phase of wound healing?

Collagen II Signup and view all the answers

What percentage of normal wound strength is achieved by day 10 following a deep clean laceration?

10% Signup and view all the answers

Which systemic factor is known to inhibit collagen synthesis in wound healing?

Protein deficiency Signup and view all the answers

What is the main characteristic of the maturation phase of wound healing?

Wound breaking strength increases Signup and view all the answers

How does diabetes mellitus affect wound healing?

Delays healing duration Signup and view all the answers

What primarily dictates the accumulation of collagen type I in wound healing beyond day 10?

Remodeling control Signup and view all the answers

Which condition is known to limit blood supply and therefore slow down wound healing?

Arterial atherosclerosis Signup and view all the answers

In which tissue repair process is pathologic repair primarily indicated?

Pathologic repair Signup and view all the answers

Which hormone is known to inhibit wound healing but may be beneficial in certain circumstances?

Glucocorticoids Signup and view all the answers

Which type of suturing technique is best described as approximating the edges of the dermis in a deep clean laceration?

Subcuticular suture Signup and view all the answers

What is the primary outcome of regeneration after acute injury?

Restitution of normal structure Signup and view all the answers

Which of the following processes is NOT associated with persistent tissue damage?

Tissue regeneration Signup and view all the answers

What primarily contributes to the increased synthesis of collagen during chronic inflammation?

Proliferation of specialized fibrogenic cells Signup and view all the answers

Which immune cells are notably activated during chronic inflammation?

Macrophages and lymphocytes Signup and view all the answers

What effect do cytokines have in the context of chronic inflammation?

Proliferation of endothelial cells Signup and view all the answers

How does fibrosis primarily differ from regeneration following injury?

Fibrosis leads to the formation of scar tissue Signup and view all the answers

Which factor is identified as the single most important cause of delayed wound healing?

Persistent infection causing inflammation Signup and view all the answers

What effect does the presence of foreign bodies have on wound healing?

They inhibit healing by prolonging the inflammatory response Signup and view all the answers

Which type of wound is likely to heal the fastest?

Sharp surgical incision Signup and view all the answers

What is the primary cause of wound dehiscence?

Excessive mechanical force applied post-surgery Signup and view all the answers

Keloids are characterized by which of the following features?

Excessive deposition of thick collagen bundles Signup and view all the answers

Which sites are likely to heal the fastest due to their vascularity?

The face Signup and view all the answers

What phenomenon occurs primarily in large surface wounds that heal by secondary union?

Wound contracture Signup and view all the answers

Excessive wound contraction can lead to which of the following deformities?

Contracture formation Signup and view all the answers

Which condition is a common underlying cause of chronic ulceration?

Arterial atherosclerosis with compromised blood flow Signup and view all the answers

What is a key distinction between hypertrophic scars and keloids?

Hypertrophic scars remain within original wound boundaries while keloids extend beyond Signup and view all the answers

Study Notes

Tissue Repair: A Look at the Processes Involved

Fibrosis: A process of tissue repair through collagen and ECM deposition, forming a scar. This occurs when tissue damage is severe or chronic, preventing regeneration by parenchymal cells alone.
Phases of Fibrosis:
- Inflammation: Removal of dead or damaged cells.
- Angiogenesis: Formation of new blood vessels.
- Fibroblast migration and proliferation: Fibroblasts migrate to the injury site and multiply.
- ECM deposition: Fibroblasts become more synthetic, producing collagen and other ECM components.
- Connective tissue remodeling: A balance between ECM synthesis and degradation, leading to increased tensile strength.
Angiogenesis Mechanisms:
- Sprouting: New vessels sprout from existing vessels.
- Angioblast-like endothelial-precursor cells (EPCs): Cells from bone marrow migrate to the site of angiogenesis.

Wound Healing: First and Second Intention

First Intention (Primary Union):
- Minor damage to keratinocytes and dermal cells with a minimal rupture of the basement membrane.
- Example: Surgical incision.
- Result: Thin fibrous union.
Second Intention (Secondary Union):
- Large defects require more inflammation, granulation tissue, collagen deposition, and wound contraction.
- Example: Deep traumatic abrasion.
- Result: Wide scar with potential for skin depression or contraction.

Wound Healing Phases: A Detailed Look

Inflammation:
- Blood clot formation.
- Chemotaxis of immune cells to the wound site.
Proliferation:
- Epithelialization: Restoration of the skin surface.
- Angiogenesis: New blood vessel formation.
- Granulation tissue formation: A mixture of fibroblasts, collagen, and blood vessels.
- Provisional matrix formation: A temporary ECM that supports the healing process.
Maturation:
- Collagen deposition: Continued accumulation of Type I collagen.
- Collagen matrix remodeling: Formation of a strong and organized collagen network.
- Wound contraction: Myofibroblasts pull the wound edges together.

Factors Influencing Wound Healing

Systemic Factors:
- Nutrition: Protein and vitamin C deficiency inhibit collagen synthesis.
- Metabolic status: Diabetes mellitus delays healing due to insulin's role in nucleic acid and protein synthesis.
- Circulatory status: Insufficient blood supply due to conditions like arterial atherosclerosis or venous stasis slows down healing.
- Steroid hormones: Glucocorticoids inhibit healing but can be beneficial in certain areas, such as the eye.
Local Factors:
- Infection: Persistent inflammation caused by infection is a major factor in delayed healing.
- Mechanical: Early tension on the wound may separate edges, delaying healing.
- Foreign bodies: Material like metal, glass, wood, or bone prolong inflammation and hinder healing.
- Anatomic location: Sites with rich vascularity (face) heal faster than sites with reduced vascularity (foot).
- Type of wound: Sharp incisions (surgical) heal faster than larger wounds (traumatic deep abrasion).

Pathologic Wound Repair: When Healing Goes Wrong

Deficient Scar Formation:
- Wound dehiscence: Separation of wound edges due to forces like vomiting or coughing.
- Wound necrosis: Death of tissue due to infection or inadequate blood supply.
Excessive Repair:
- Hypertrophic scar: Excess collagen deposition, raised and itchy, but stays within the boundaries of the original wound.
- Keloid: Excess collagen deposition extending beyond the original wound boundaries, often with genetic predisposition.
Contracture Formation:
- Deformity caused by excessive wound contraction, often seen after burns.

Chronic Ulceration: A Persistent Wound

Arterial atherosclerosis: Compromised blood flow leading to chronic ulceration, especially in the lower extremities.
Venous stasis: Reduced venous return to the heart, also leading to chronic ulceration.

Summary: Responses After Injury and Inflammation

Cellular and vascular responses:
- Stimulus removal (acute injury):
  - Parenchymal cell death (intact tissue framework) - Regeneration: Restitution of normal structure.
- Persistent tissue damage:
  - Parenchymal cell death (damaged tissue framework) - Repair: Scar formation.
  - Fibrosis: Tissue scar (chronic inflammatory diseases).

Fibrosis: An Ongoing Process

Persistent stimulus (chronic inflammation):
- Macrophage and lymphocyte activation:
  - Growth factors: PDGF, FGF, TGF-β.
  - Cytokines: TNF, IL-1, IL-4, IL-13.
  - Reduced metalloproteinase activity.
- Increased proliferation of fibroblasts, endothelial cells, and specialized fibrogenic cells.
- Increased collagen synthesis and decreased collagen degradation.
- Ultimately leading to fibrosis.

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Description

This quiz explores the mechanisms of tissue repair, specifically focusing on fibrosis and the processes involved in wound healing. It includes detailed phases of fibrosis, angiogenesis mechanisms, and the differences between first and second intention healing. Understand the essential steps that lead to tissue recovery and regeneration.