AIM Step 10
3rd Year MBBS
Pathology
3rd Year MBBS
Pathology
Student Memory Support
Repair by Scarring, Growth Factors and Extracellular Matrix
High-yield memory reinforcement for rapid KMU exam revision.
1. High-Yield Flashcards
Tap each question to reveal the answer.
When does repair by scarring become important?
When complete regeneration cannot restore tissue, especially after extensive injury or loss of the ECM framework.
What are the main components of granulation tissue?
New capillaries, proliferating fibroblasts, inflammatory cells, and loose extracellular matrix.
Which cell coordinates many important events in wound repair?
The macrophage, through debris removal and release of growth factors and cytokines.
Which growth factor is the major stimulus for angiogenesis during repair?
VEGF.
Which growth factor has a major fibrogenic role in healing?
TGF-β, which increases ECM production and reduces matrix degradation.
Which growth factor promotes fibroblast migration and proliferation?
PDGF.
Which receptor type is used by EGF, VEGF, PDGF, and FGF?
Receptor tyrosine kinases.
Through which signaling system does TGF-β mainly act?
Serine/threonine kinase receptors with SMAD-dependent signaling.
What are the three major groups of extracellular matrix components?
Fibrous structural proteins, adhesive glycoproteins, and proteoglycans/glycosaminoglycans.
Which ECM protein provides most of the tensile strength of a scar?
Collagen.
Which proteins are characteristic components of basement membrane?
Type IV collagen and laminin.
What is the main role of MMPs during scar maturation?
They degrade extracellular matrix during remodeling.
What is the function of TIMPs?
They inhibit matrix metalloproteinases and help control ECM degradation.
Which cells are mainly responsible for wound contraction?
Myofibroblasts.
What distinguishes a keloid from a hypertrophic scar?
A keloid extends beyond the original wound margins; a hypertrophic scar remains within them.
2. Mnemonics
Mnemonic Title: Steps of Scar Formation
Mnemonic Word: I-A-F-D-R
Meaning: Inflammation → Angiogenesis → Fibroblast activity → Deposition of ECM → Remodeling
Mnemonic Word: I-A-F-D-R
Meaning: Inflammation → Angiogenesis → Fibroblast activity → Deposition of ECM → Remodeling
Mnemonic Title: Main ECM Groups
Mnemonic Word: FAP
Meaning: Fibrous proteins → Adhesive glycoproteins → Proteoglycans/GAGs
Mnemonic Word: FAP
Meaning: Fibrous proteins → Adhesive glycoproteins → Proteoglycans/GAGs
Mnemonic Title: Major Factors Delaying Healing
Mnemonic Word: I-P-M-F-D-G
Meaning: Infection → Poor perfusion → Mechanical stress → Foreign bodies → Diabetes → Glucocorticoids
Mnemonic Word: I-P-M-F-D-G
Meaning: Infection → Poor perfusion → Mechanical stress → Foreign bodies → Diabetes → Glucocorticoids
3. Memory Tables
Hypertrophic Scar vs Keloid
| Feature | Hypertrophic Scar | Keloid |
|---|---|---|
| Wound boundary | Remains within original injury | Extends beyond original injury |
| Main abnormality | Excess collagen deposition | Marked excessive collagen deposition |
Granulation Tissue vs Mature Scar
| Feature | Granulation Tissue | Mature Scar |
|---|---|---|
| Vascularity | High | Low |
| Fibroblasts | Numerous and active | Reduced |
| Matrix | Loose ECM | Dense organized collagen |
| Appearance | Red and soft | Pale and firm |
4. Rapid Revision Points — Last-Minute Revisio
Must Remember:
- Scar formation follows inflammation → angiogenesis → fibroblast activity → ECM deposition → remodeling.
- Granulation tissue is highly vascular and contains fibroblasts in loose ECM.
- VEGF is the major angiogenic mediator in repair.
- TGF-β promotes fibrosis by increasing ECM synthesis and reducing degradation.
- Collagen provides tensile strength; elastin provides elasticity.
- Fibronectin and laminin are important adhesive glycoproteins.
- MMPs degrade ECM; TIMPs restrain MMP activity.
- Infection delays healing by prolonging inflammation and causing additional tissue injury.
- Poor perfusion limits oxygen and nutrient delivery to healing tissue.
- Glucocorticoids impair healing by suppressing inflammation and collagen synthesis.
- Excessive wound contraction may produce a contracture.
KMU Exam Trap: Hypertrophic scars stay within the original wound margins, whereas keloids extend beyond them.
5. Clinical Memory Hooks
Deep tissue injury with destroyed ECM framework → regeneration becomes inadequate → fibrosis and scar formation.
Red, soft healing tissue that bleeds easily → numerous delicate new capillaries → granulation tissue.
Contaminated wound with persistent inflammation → infection delays progression toward mature scar formation.
Raised scar extending into surrounding normal skin → excessive collagen deposition → keloid.
Scar crossing a joint with restricted movement → excessive myofibroblast contraction → contracture.
6. Starred High-Yield Exam Points
- ⭐ TGF-β is the major fibrogenic mediator: increased ECM synthesis + reduced matrix degradation.
- ⭐ VEGF is the key growth factor driving angiogenesis during repair.
- ⭐ Loss of the extracellular matrix framework favors scar formation rather than complete regeneration.
- ⭐ Mature scar shows dense organized collagen with reduced vascularity and cellularity.
- ⭐ MMPs degrade extracellular matrix; TIMPs inhibit MMP activity during remodeling.
- ⭐ Keloid extends beyond the original wound margins; hypertrophic scar does not.
- ⭐ Excessive myofibroblast-mediated contraction produces contracture and may restrict movement.