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Questions and Answers
What is the primary role of myofibroblasts in wound healing?
What is the primary role of myofibroblasts in wound healing?
Which is not a characteristic of healing by first intention?
Which is not a characteristic of healing by first intention?
At what time post-injury do macrophages replace neutrophils in the healing process?
At what time post-injury do macrophages replace neutrophils in the healing process?
What occurs during the fifth day of healing by first intention?
What occurs during the fifth day of healing by first intention?
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What is a consequence of delayed contraction in wound healing?
What is a consequence of delayed contraction in wound healing?
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What is a key feature of granulation tissue?
What is a key feature of granulation tissue?
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How long does it typically take to achieve normal epidermal thickness during wound healing?
How long does it typically take to achieve normal epidermal thickness during wound healing?
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What is not a part of the scar formation process within one month after injury?
What is not a part of the scar formation process within one month after injury?
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What is the primary role of macrophages during the demolition stage of fracture healing?
What is the primary role of macrophages during the demolition stage of fracture healing?
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What is the primary function of macrophages in the tissue repair process after neutrophils are largely replaced?
What is the primary function of macrophages in the tissue repair process after neutrophils are largely replaced?
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Which process begins with the development of capillary loops and mesenchymal cells during fracture healing?
Which process begins with the development of capillary loops and mesenchymal cells during fracture healing?
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Which cells differentiate from mesenchymal cells to form either woven bone or cartilage in the healing process?
Which cells differentiate from mesenchymal cells to form either woven bone or cartilage in the healing process?
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Which histological type of bone is characterized by collagen fibers arranged in parallel sheets?
Which histological type of bone is characterized by collagen fibers arranged in parallel sheets?
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What characterizes the 'callus' during the early stages of fracture healing?
What characterizes the 'callus' during the early stages of fracture healing?
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During which stage of fracture healing does hematoma formation occur?
During which stage of fracture healing does hematoma formation occur?
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During the formation of lamellar bone, what is the primary function of osteoblasts?
During the formation of lamellar bone, what is the primary function of osteoblasts?
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What role do fibroblasts play in scar formation?
What role do fibroblasts play in scar formation?
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What is the significance of Haversian systems formed during lamellar bone formation?
What is the significance of Haversian systems formed during lamellar bone formation?
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What occurs during wound contraction in large surface wounds?
What occurs during wound contraction in large surface wounds?
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What ultimately happens during the remodelling stage of bone healing?
What ultimately happens during the remodelling stage of bone healing?
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Which process does NOT typically occur in the second week of the healing process?
Which process does NOT typically occur in the second week of the healing process?
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Which component is primarily responsible for the osteoclastic removal of the provisional callus?
Which component is primarily responsible for the osteoclastic removal of the provisional callus?
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What characterizes the inflammatory response during the second stage of fracture healing?
What characterizes the inflammatory response during the second stage of fracture healing?
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Study Notes
Introduction to Pathology Lecture 4
- The lecture covers wound healing, fractures, and special tissues.
- Healing, in a pathological context, is the replacement of damaged tissue with healthy tissue.
Wound Healing
- A wound is a break in the structure of living tissue.
- It results from injury and involves an inflammatory response.
- Wounds can be accidental or surgical.
Types of Wounds
- Closed Wounds: The skin surface is intact, but underlying tissues are damaged (e.g., contusions, hematomas, Stage 1 pressure ulcers).
- Open Wounds: The skin is broken, and underlying tissues are exposed to the environment.
Processes of Wound Healing
- Regeneration: Lost tissue is replaced by similar tissues.
- Repair: Loss of tissue is replaced by granulation tissue, which matures to form scar tissue.
Types of Cells
- Labile Cells: High capacity for proliferation, found in surface epithelium of the gastrointestinal tract, urinary tract, or skin. (e.g., epithelial cells of the skin, lining of digestive tract). Excellent regeneration chances.
- Stable Cells: Moderate capacity for proliferation, found in tissues like liver, endocrine glands, and renal tubular epithelium. Good regeneration chances.
- Permanent Cells: Limited or no capacity for proliferation, like neurons or cardiac muscle cells.
Objectives of Wound Healing
- Restoration of an intact epithelial surface.
- Restoration of tensile strength of the sub-epithelial tissue.
- Involved seven processes: acute inflammatory response; regeneration of native cells of tissue involved; proliferation and migration of native and connective tissue cells; synthesis of extracellular matrix (ECM) proteins; remodelling of connective tissue; collagenization and progressive acquisition of wound strength; and contraction of wound edges.
Growth Factors
- Mediated by low molecular weight polypeptides.
- Stimulate cell division and proliferation.
- Sources include platelets, serum growth factors, macrophages, and lymphocytes.
Healing by Regeneration
- The renewal of lost tissue by replacing lost cells with identical ones.
- Involves two processes: proliferation of surviving cells and migration of these cells into the vacant space.
- Capacity depends on proliferative ability, degree of damage to stroma, and type/severity of damage.
Wound Contraction
- Mechanical reduction in the wound size.
- Reduction of wound size, faster healing since less tissue needs to be replaced.
- Prevented healing—slow healing with a larger scar.
- Causation is by myofibroblasts, having features between fibroblasts and smooth muscle cells.
- Migrate into the wound and contract, thus decreasing the wound size.
Patterns of Wound Healing
-
Healing by First Intention (Primary Union): Clean uninfected wounds approximated by sutures heal well.
- Minimal epithelial & connective tissue cell death.
- Immediate clotting.
- Dehydration forms a scab.
- Process includes neutrophils invasion, basal cell proliferation, epidermal thickening, and epithelial cell fusion to form a continuous epithelium
-
Healing by Second Intention: Extensive loss of cells and/or wide margins resulting in a large tissue defect.
- Requires abundant granulation tissue formation.
- More fibrin, necrotic debris, and need for an intense inflammatory reaction.
- Important for wound contraction
Granulation Tissue
- A new connective tissue with blood vessels and fibroblasts necessary for wound healing.
- It fills the wound space and facilitates wound contractions.
Factors Influencing Wound Healing
- Local Factors: wound size/location/type, vascular supply, infection, movement, ionizing radiation.
- Systemic Factors: circulatory status, infection, metabolic status, nutritional deficiencies, anti-inflammatory drugs.
Complications of Wound Healing
-
Infection: Pathogens enter a wound and delay or prevent healing.
-
Deficient Scar Formation: Inadequate granulation tissue formation or an inability to produce a suitable extracellular matrix. Complications include: -Wound dehiscence/incisional hernias : improper suturing or mechanical stress that will cause the wound to split open leading to abdominal organs protruding outside - Ulceration :inadequate blood supply or lack of sensation in the wound area.
-
Excessive Scar Formation: Deposition of excess extracellular matrix. This could result in a hypertrophic scar or keloid.
Fracture Healing
- Unlike skin wounds; fracture healing involves specialized bone-forming tissue.
- Steps required for fracture healing: haematoma formation ; inflammation; destruction; formation of granulation tissues; formation of woven bone and cartilages; formation of lamellar bones, and remodelling.
Bone Structure
- Calcified osteoid tissue with collagen fibers embedded in the mucoprotein matrix (osteomucin).
- Two types of bones: 1.) Woven (irregular collagen arrangement); 2.) Lamellar (parallel collagen bundles).
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Description
This lecture focuses on wound healing, fractures, and special tissues. It explains the processes of healing, including regeneration and repair, as well as the types of wounds and cells involved in the healing process.
