Tissue Repair and Anatomy Quiz

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Questions and Answers

What is the primary purpose of repair in tissue?

To induce cell death in damaged tissues

To prevent any form of tissue regeneration

To promote inflammation in the affected area

To restore tissue architecture and function after injury (correct)

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

Extracellular matrix (ECM)

Epithelial cells (correct)

Support (stromal) cells

Blood vessels and lymphatic vessels

What are the two main processes involved in tissue repair?

Angiogenesis and fibrosis

Regeneration and connective tissue deposition (correct)

Cellular apoptosis and necrosis

Inflammation and tissue remodeling

Which cell type is primarily responsible for producing the extracellular matrix in connective tissue?

Fibroblasts Signup and view all the answers

In the context of skin anatomy, which statement is true about the dermis?

It provides a mesh of elastin and collagen fibers Signup and view all the answers

Which type of tissue is characterized by cells that are continuously dividing?

Labile tissue Signup and view all the answers

What is the role of fibroblasts during tissue repair?

They are the source of fibrous or scar tissue. Signup and view all the answers

What does the term 'intrinsic proliferative capacity' refer to?

The inherent ability of a tissue to repair itself. Signup and view all the answers

Which tissue type has minimal proliferative capacity but can enter cell division in response to injury?

Stable tissue Signup and view all the answers

In the context of tissue repair, what is the primary function of vascular endothelial cells?

To provide nutrients and growth factors. Signup and view all the answers

What distinguishes permanent tissue from other tissue types?

It is made up of cells that do not proliferate. Signup and view all the answers

Which of the following is an example of labile tissue?

Gastrointestinal epithelium Signup and view all the answers

During tissue repair, which phase of the cell cycle is associated with resting cells?

G0 phase Signup and view all the answers

Which of the following tissues have a limited capacity for regeneration?

Neurons Signup and view all the answers

What is the primary mechanism through which liver regeneration occurs?

Cytokine priming and growth factor stimulation Signup and view all the answers

Which of the following statements regarding tissue regeneration is true?

Fibrosis occurs in response to severe tissue injury. Signup and view all the answers

What role do growth factors play in cell replication?

Promote cell survival and proliferation Signup and view all the answers

What happens to cardiac muscle cells after a myocardial infarction?

They are replaced by non-functioning scar tissue. Signup and view all the answers

What must occur for liver regeneration to be successful?

Residual liver tissue must be structurally intact. Signup and view all the answers

Which of the following conditions cannot be repaired solely through regeneration?

A chronic liver disease Signup and view all the answers

What is a major consequence of connective tissue deposition following tissue death?

Formation of scar tissue Signup and view all the answers

What happens to the liver cells following extensive destruction when the reticulin framework is damaged?

The capacity for liver cell regeneration results in scar formation. Signup and view all the answers

During which phase of repair does the formation of granulation tissue occur?

Proliferative phase Signup and view all the answers

What primarily characterizes healing by primary intention?

It typically involves well-approximated surgical incisions. Signup and view all the answers

What is the role of matrix metalloproteinases during the remodeling phase?

They degrade the extracellular matrix, including collagen. Signup and view all the answers

What does granulation tissue mainly consist of?

Fibroblasts, thin-walled blood vessels, and extracellular matrix Signup and view all the answers

In healing by secondary intention, what typically occurs?

It involves a larger wound healing response with more inflammation. Signup and view all the answers

What initiates the inflammatory phase of tissue repair?

Secretion of cytokines and growth factors Signup and view all the answers

What mainly happens during the remodeling phase of repair?

The collagen structure of the scar is organized and matured. Signup and view all the answers

What is a common cause of arterial ulcers?

Atherosclerosis of peripheral arteries Signup and view all the answers

Which type of excessive tissue repair results in a scar that extends beyond the wound boundary?

Keloid scar Signup and view all the answers

What pathological consequence arises from inadequate wound healing?

Wound dehiscence Signup and view all the answers

Which of the following statements is true regarding venous leg ulcers?

They arise from chronic venous hypertension. Signup and view all the answers

What characterizes healing by secondary intention compared to primary intention?

More intense inflammatory response Signup and view all the answers

When does healed skin reach approximately 70-80% of normal skin strength?

3 months Signup and view all the answers

What condition is exhibited by 'proud flesh'?

Exuberant granulation tissue Signup and view all the answers

When does tissue repair primarily occur through connective tissue deposition?

When the structural framework is damaged Signup and view all the answers

What is a potential complication of inadequate tissue repair?

Wound dehiscence Signup and view all the answers

Which factor is likely to hinder the tissue repair process significantly?

Vitamin C deficiency Signup and view all the answers

What is primarily responsible for the excessive formation of fibroblasts and extracellular matrix in desmoid tumors?

Exuberant proliferation of fibroblasts Signup and view all the answers

Which type of ulcer is multifactorial and includes factors such as ischemia and neuropathy?

Diabetic ulcers Signup and view all the answers

What outcome does extensive injury typically result in?

Increased connective tissue deposition Signup and view all the answers

Which of the following is not a factor that influences tissue repair?

Cultural background Signup and view all the answers

Which healing process is typically associated with a larger tissue defect that needs to be replaced?

Healing by secondary intention Signup and view all the answers

What primarily predominates over epithelial regeneration in healing by secondary intention?

Fibrosis Signup and view all the answers

Study Notes

Regeneration and Repair

Regeneration and repair are processes that restore tissue architecture and function after injury.
Regeneration involves the proliferation of surviving cells to replace the damaged or lost tissue.
Connective tissue deposition involves laying down fibrous connective tissue to replace damaged tissue when regeneration is not possible.

Learning Objectives

Describe the effects of regeneration and repair on an organ or tissue.

Outline

Introduction
Regeneration
Connective tissue deposition
Cutaneous wound healing
Pathological aspects of repair

Terminology

Connective tissue: Tissues providing structure, mechanical strength and support for specialized tissues.
Connective tissue structure components:
- Extracellular matrix (ECM): fibrous structural proteins (e.g., collagen), ground substance and basement membrane.
- Support cells (stromal cells): Responsible for making ECM (e.g., fibroblasts).
- Blood vessels, lymphatic vessels and nerves: Providing nutrients and factors required for tissue growth.

Organ Examples

Skin (cutaneous organ):
- Specialized tissue: epidermis (outer epithelial cell layer).
- Connective tissue: dermis (mesh of elastin and collagen fibers).
Liver (parenchymal/solid organ):
- Specialized tissue: hepatocytes (type of parenchymal cell).
- Connective tissue: delicate network of extracellular matrix (e.g., reticulin).

Terminology Continued

Collagen: Main fiber type in connective tissue, excess deposition is called fibrosis or scar formation.

Tissue Repair

Regeneration alone is not practical for humans in most cases.
Instead, a combination of regeneration and connective tissue repair is relied upon.
Several cell types proliferate during repair:
- Surviving functional cells.
- Vascular endothelial cells (provide nutrients and growth factors).
- Fibroblasts (source of fibrous/scar tissue).
Ability of a tissue to repair itself is the intrinsic proliferative capacity.

Proliferative Capacity

Different cells have various regenerative capacities.
A cell's intrinsic proliferation capacity depends on how much time is spent in different phases of the cell cycle.
- G₀: Resting phase.
- Active phases: Remaining phases of the active cell cycle (G₁, S, G₂ & M).

Three Main Tissue Types

Body tissues are categorized based on their proliferative capacity.
- Labile tissue: Consistently divides; high regenerative capacity. (e.g., gastrointestinal epithelium, skin, oral mucosa, bone marrow.)
- Stable tissue: Minimal proliferation, but capable of entering G₁ in response to injury. (e.g., cells of connective tissue like fibroblasts and smooth muscle cells; solid organs such as kidney, pancreas, adrenal glands.)
- Permanent tissue: Cannot proliferate (e.g., neurons and cardiac muscle cells)

Labile Tissues

Have high regeneration capacity; continuous cell renewal.
Increased amount of stem cells. Rapid cell replacement in injury.
Stem cells differentiate into the lost cell type.

Stable Tissues

Regeneration can occur but is often limited.
Connective tissue-like cells (fibroblasts, smooth muscle cells).
Many solid organs are stable tissues (kidney, pancreas) but one exception is the liver.

Permanent Tissues

Cannot undergo proliferation.
Tissue death results in repair via connective tissue deposition.
Results in non-functioning scar tissue.
Examples include neurons and cardiac muscle cells.

Regeneration Process

Complex process involving the interaction of growth signals and control mechanisms.
Influenced by growth factors, hormones and cytokines.
Interaction of cells with the ECM.
Mechanical support; scaffolding for tissue repair, and microenvironment maintenance.

Example: Liver Regeneration

Occurs through priming and proliferation phases.
Priming: Kupffer cell cytokines (IL-6) make hepatocytes respond to growth factors.
Proliferation: Growth factors (HGF, TGF-α) stimulate hepatocyte entry into the cell cycle.

Limitations of Regeneration

Regeneration cannot repair all types of injuries.
Regeneration often isn't sufficient for severe or chronic injuries.
Tissues with non-dividing cells cannot be regenerated.
Connective tissue deposition results in fibrosis/scar tissue formation.
Specific examples for liver (intact structure needed for regeneration; regeneration insufficient with inflammation/infection, with extensive damage to reticulin).

Repair by Connective Tissue Deposition

Inflammatory phase: process begins within 24 hours, damaged tissue removed, cytokines and growth factors secreted.
Proliferative phase: new blood vessels (angiogenesis), fibroblasts proliferate and deposit ECM, granulation tissue is formed.
Remodeling phase: granulation tissue becomes a scar, matrix metalloproteinases degrade ECM, including collagen.

Cutaneous Wound Healing

Involves epithelial regeneration and connective tissue formation.
Healing processes grouped into primary, secondary or tertiary intent based on wound size, health and repair procedure used.
Extensive vs minimal tissue types repaired ( primary vs secondary intention healing.)

Healing: Primary Intention

Clean, uninfected opposed wound.
Example: sutured incision.
Epithelial regeneration predominates over fibrosis.
Minimal wound contraction and scar formation.
Dermal appendages are often lost.

Healing: Secondary Intention

Large, infected, or chronic wounds.
Example: ulcers, deep abrasions, severe burns.
Fibrosis predominates over epithelial regeneration.
More severe inflammatory response.
Extensive granulation tissue and scar formation.

Wound Strength

Healed skin is not as strong as original tissue.
Strength increases over time after repair, but not to the original strength. Recovery time depends on depth and extent of tissue damage

Pathological Aspects of Repair

Complications of wound healing classified into inadequate and excessive tissue repair.

Factors Influencing Tissue Repair

Factors influencing wound healing (infection, foreign body presence, nutritional status - vitamins (C), hormonal status (steroids), perfusion/blood supply/oxygen, diabetes, mechanical factors such as pressure, type and extent of injury (labile vs. stable permanent tissue.))

Inadequate Tissue Repair

Results from inadequate formation process components.
Examples include:
- Wound dehiscence: separation of surgical wound edges. (infection, mechanical factors)
- Ulcers (venous leg ulcers - chronic venous hypertension, poor oxygen delivery; arterial ulcers - atherosclerosis, and diabetic ulcers – multifactorial)
- Pressure ulcers (mechanical pressure, local ischemia)

Excessive Tissue Repair

Results from excess formation process components.
Examples include:
- Hypertrophic scars: raised scars that do not go beyond original wound.
- Keloid scars: raised scars that extend beyond original wound.
- Proud flesh: exuberant granulation tissue
- Wound contractures
- Desmoid tumors: excess proliferation of fibroblasts and ECM.

In Summary

Tissue repair can occur via regeneration or connective tissue deposition.
Body tissues have different regeneration capacities.
Tissues are repaired by replacement with connective tissue and scar tissue.
Inadequate or excessive repair can cause health problems depending on the type/extent of tissue damage and presence of infections or foreign bodies.

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Description

Test your knowledge on the essential concepts of tissue repair and its various components. This quiz covers the roles of different cell types, the processes involved in tissue healing, and the characteristics of various tissue types. Perfect for students studying biology or anatomy.