Tissue Repair and Regeneration Basics

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Questions and Answers

Which type of tissue is characterized by its ability to regenerate after injury?

Inelastic tissue

Permanent tissue

Labile tissue (correct)

Stable tissue

What is a common complication associated with inadequate tissue repair after an injury?

Excessive scarring

Wound fibrosis

Wound dehiscence (correct)

Prolonged inflammation

Which of the following factors can prolong the inflammation phase of healing?

Mechanical factors (correct)

Vitamin C intake

Adequate perfusion

Nutritional excellence

What is the typical skin strength at 3 months after sutured wound healing?

70-80% Signup and view all the answers

Which statement is true regarding healing by secondary intention?

It leads to extensive granulation tissue formation. Signup and view all the answers

How does diabetes mellitus affect tissue repair?

Leads to microvascular disease. Signup and view all the answers

What differentiates inadequate tissue repair from excessive tissue repair?

Inadequate formation of repair components Signup and view all the answers

Which of the following tissues is classified as a stable tissue?

Lung Signup and view all the answers

What is a key factor that influences the proliferation of cells during regeneration?

Cytokines Signup and view all the answers

Which of the following is a potential consequence of glucocorticoids on the healing process?

Suppression of immune response Signup and view all the answers

During liver regeneration, what initiates the priming phase for hepatocytes?

Interleukin-6 Signup and view all the answers

Which of the following injuries can regeneration alone not repair?

Injury to permanent tissues Signup and view all the answers

What occurs after a myocardial infarction that leads to reduced cardiac function?

Connective tissue deposition Signup and view all the answers

In which phase of liver regeneration do growth factors stimulate entry into the cell cycle?

Proliferation phase Signup and view all the answers

Which organ has an exceptional capacity for regeneration, allowing it to recover even after significant resection?

Liver Signup and view all the answers

What main outcome results from connective tissue deposition when tissue death occurs?

Reduced organ function due to scar tissue Signup and view all the answers

What are the factors primarily influencing whether tissue can regenerate after injury?

Intrinsic proliferation capacity of the cells Signup and view all the answers

Which type of ulcer is specific to poor oxygen delivery due to chronic venous hypertension?

Venous leg ulcers Signup and view all the answers

Which of the following conditions can result from excessive tissue repair?

Proud flesh Signup and view all the answers

What type of scar extends beyond the original wound boundary?

Keloid scar Signup and view all the answers

In which scenario would scar formation primarily occur instead of tissue regeneration?

In damaged structural frameworks Signup and view all the answers

Which of the following healing processes refers to tissue granulation through secondary intention?

Healing with significant tissue loss Signup and view all the answers

What is the primary cause of pressure ulcers?

Mechanical pressure on the skin Signup and view all the answers

Which of the following describes a condition characterized by an exuberant proliferation of fibroblasts and ECM?

Desmoid tumor Signup and view all the answers

Study Notes

Regeneration and Repair

Regeneration and repair are the two main processes of tissue repair.
Repair restores tissue architecture and function after injury.
Regeneration involves the proliferation of surviving cells to replace damaged or lost tissue.
Connective tissue deposition occurs when repair can't be accomplished by regeneration alone, involving fibrous connective tissue to replace the damaged tissue. This results in fibrosis or scar formation.

Terminology

Connective tissue provides structure, mechanical strength, and support for specialized tissues.
Connective tissue consists of extracellular matrix (ECM) and supporting cells.
ECM includes fibrous structural proteins (e.g., collagen), ground substance, and basement membrane.
Supporting cells create the ECM, and examples include fibroblasts.
Blood vessels, lymphatic vessels, and nerves provide nutrients and factors for tissue growth.

Organ-Based Examples

Skin comprises specialized epidermal tissue and a dermis with elastin and collagen fibers.
Liver contains hepatocytes and a reticulin-rich connective tissue framework.

Tissue Repair

Regeneration alone isn't sufficient for most human tissue repair.
Various cell types, including surviving functional cells, vascular endothelial cells, and fibroblasts, play roles during repair.
Fibroblasts produce fibrous/scar tissue
A tissue's inherent capacity for repair is its intrinsic proliferative capacity.

Proliferative Capacity and Cell Cycle

Cell types have varying regeneration capacities.
A cell's intrinsic proliferative capacity is associated with the portion of the cell cycle it predominantly occupies.
The resting phase is Go, whereas other phases are actively engaged in the cell cycle.

Three Main Tissue Types

Body tissues are categorized based on proliferative capacity:
- Labile: continuously divide (e.g., gastrointestinal epithelium, skin).
- Stable: minimal division (e.g., connective tissue cells, some organs).
- Permanent: unable to divide (e.g., neurons, cardiac muscle).

Labile Tissues

Labile tissues have high regeneration capacity, continuous renewal, and substantial stem cell populations.
Injury-induced rapid replacement happens through cell proliferation or stem cell differentiation.
Examples include gastrointestinal epithelium, skin, oral mucosa, and bone marrow.

Stable Tissues

Stable tissues permit regeneration but with limitations.
Connective tissue cells and several solid organs possess limited regeneration capacity.
Liver regeneration is an exception, capable of regeneration even if up to 90% of the liver is removed.

Permanent Tissues

Permanent tissues have no proliferative capacity
Injury results in connective tissue deposition and non-functional scar tissue, which reduces organ functionality.
Neurons & cardiac muscle cells are examples.

Regeneration

Regeneration is a complex process influenced by growth factors, hormones, cytokines, and cell interactions with the ECM.
Growth factors, hormones, cytokines, cell-ECM interaction, mechanical support, and microenvironment maintenance are influential.
Factors promote proliferation, survival, migration, differentiation, and maintain repair.

Example: Liver Regeneration

Liver regeneration relies on two major mechanisms.
Priming involves Kupffer cells releasing cytokines (e.g., IL-6), preparing hepatocytes for growth factor responses.
Proliferation depends on growth factors such as HGF and TGFα to stimulate hepatocyte entry into the cell cycle.

Limitations of Regeneration

Regeneration is limited by severe or chronic injuries, harm to connective tissue, and damage to non-dividing cells.
Connective tissue deposition leads to fibrosis or scarring in these cases, resulting in impaired organ function.
Extensive tissue damage or chronic inflammation can lead to scar formation in the liver , even if the remaining cells have regenerative capacity

Limitations of Regeneration: Liver

Regeneration depends on intact residual tissue structure.
Damage from infection or inflammation impairs regeneration and stimulates connective tissue deposition.
In severe liver damage, scar formation is possible, even with remaining liver cells' regenerative potential.

Repair by Connective Tissue Deposition

Wound healing involves three phases:
- Inflammatory: Removing damaged tissue with cytokines and growth factors.
- Proliferative: Forming new blood vessels (angiogenesis), fibroblasts, granulation tissue with other ECM components.
- Remodeling: Scar remodeling by matrix metalloproteinases degrading ECM.

Cutaneous Wound Healing

Cutaneous wound healing involves various stages with two primary categories:
- Primary intention (e.g., surgical incisions): minimal scarring due to precise wound edges and minimal tissue loss.
- Secondary intention (e.g., ulcers): larger wounds with significant tissue loss or delayed closure, resulting in greater scar formation.

Healing by Primary Intention

Healing of clean, uninfected, precisely aligned wounds with minimized tissue loss.
Epithelial regeneration predominates
Small scars and minimal wound contraction are typical results.

Healing by Secondary Intention

Extensive tissue loss or chronic injuries result in larger wound areas, with more inflammatory response, substantial granulation tissue, and considerable scar formation.
Fibrosis predominates over epithelial regeneration.

Wound Strength

Fully healed skin is usually weaker than original.
Sutured wounds require time for progressive enhancement of wound strength (e.g., from minimal strength after 7-10 days to near-normal strength after several months)

Pathological Aspects of Repair

Wound healing complications fall into two categories:
- Inadequate repair: Wound dehiscence, ulcers, infections.
- Excessive repair: Hypertrophic scars, keloids.

Factors Influencing Tissue Repair

Factors influencing tissue repair include infection, foreign bodies, nutritional status, glucocorticoids, poor tissue perfusion, mechanical factors , and diabetes.
Extent and type of injury, and the type of tissue, also influence the outcome.

Inadequate Tissue Repair Examples

Wound dehiscence: separation of wound edges.
Ulcers: venous or arterial ulcers, diabetic ulcers, pressure ulcers.

Excessive Tissue Repair Examples

Hypertrophic scar: raised scar within original wound perimeter.
Keloid scar: raised scar extending beyond wound border.
Proud flesh: exuberant granulation tissue.
Wound contractures: Excessive scar tissue contraction.
Desmoid tumors: Fibroblast and ECM excess proliferation.

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Description

This quiz explores the processes of tissue repair, including regeneration and the role of connective tissue. It covers key terminology related to extracellular matrix and supporting cells, as well as examples from organ systems. Test your knowledge on how tissues restore and regenerate after injury.