CR1 KCP1 Healing & Repair

Differentiate between Regeneration and Repair (Healing by Scarring).

Regeneration replaces damaged cells with the same cell type (restores normal function; requires intact ECM). Repair replaces damaged tissue with fibrous scar tissue (occurs when ECM is destroyed or cells cannot divide).

Define Labile, Stable, and Permanent cells and give 2 examples of each.

Labile: Continuously divide (Epidermis, GI epithelium). Stable: Quiescent (G0), divide upon injury (Hepatocytes, Endothelial cells). Permanent: Non-dividing, form scars upon injury (Neurons, Cardiac myocytes).

Differentiate between Autocrine, Paracrine, and Endocrine signaling in tissue repair.

Autocrine: Cell responds to its own secreted factors (liver regeneration). Paracrine: Cell responds to factors from nearby cells (wound healing). Endocrine: Hormones travel through blood to distant cells.

What are the key roles of VEGF, PDGF, and TGF-β in wound healing?

VEGF: Induces Angiogenesis (blood vessel sprouting). PDGF: Stimulates migration/proliferation of fibroblasts & smooth muscle. TGF-β: Primary stimulator of collagen deposition/fibrogenesis.

Name the 4 continuous and overlapping phases of skin wound healing in correct order.

1. Hemostasis → 2. Inflammation (Neutrophils then Macrophages) → 3. Proliferation (Granulation tissue & Collagen) → 4. Remodeling (Maturation & Matrix Metalloproteinases).

What is Granulation Tissue? State its gross appearance and microscopic components.

Gross: Pink, soft, beefy red, granular area that bleeds easily. Microscopic: Proliferating capillaries (Angiogenesis), Fibroblasts, loose ECM, edema, and macrophages.

Outline the main steps of Angiogenesis by vessel sprouting.

1. Vasodilation (VEGF) → 2. BM degradation by MMPs & pericyte detachment→ 3. Endothelial tip cell migration → 4. Endothelial proliferation & tube formation → 5. Pericyte recruitment & maturation.

What enzymes remodel collagen during scar maturation and what cells produce them?

Matrix Metalloproteinases (MMPs) (interstitial collagenases, gelatinases, stromelysins). Produced by macrophages, neutrophils, and fibroblasts.

Compare Primary Intention and Secondary Intention based on wound margins and tissue loss.

Primary Intention: Clean surgical incision, minimal tissue loss, closely approximated margins (sutured). Secondary Intention: Large tissue defect, unapproximated edges, significant tissue loss or infection.

List 3 major physiological differences between Primary and Secondary Intention healing.

Secondary Intention has: 1. Larger clot and more intense inflammation; 2. Abundant granulation tissue formation; 3. Marked wound contraction mediated by myofibroblasts.

Describe the timeline of cell dominance in Primary Intention (24h, 3 days, 5 days).

24 hours: Neutrophils enter clot. 3 days: Macrophages replace neutrophils; granulation tissue forms. 5 days: Granulation tissue fills space; collagen bridges closure line.

What is the maximum tensile strength a healed skin scar can achieve compared to unwounded skin?

70% to 80% of original strength (achieved by ~3 months).

List 4 local factors that impair wound healing.

1. Persistent infection; 2. Presence of foreign material (dirt, sutures, glass); 3. Inadequate blood supply (ischemia); 4. Excessive movement / mechanical stress.

List 4 systemic factors that impair wound healing.

1. Nutritional deficiencies (Vitamin C, Zinc, Protein); 2. Diabetes Mellitus (microangiopathy); 3. Systemic Corticosteroids; 4. Advanced age / Circulatory disorders.

Differentiate between a Hypertrophic Scar and a Keloid.

Hypertrophic Scar: Excessive collagen remains within the boundaries of original wound. Keloid: Excessive collagen grows beyond the original wound margins and does not spontaneously regress.

Define Wound Dehiscence, Ulceration, and Wound Contracture.

Dehiscence: Wound rupture/gaping (common in abdominal incisions). Ulceration: Wound breakdown from inadequate blood supply/neuropathy. Contracture: Excessive contraction causing joint stiffness/deformity (common after deep burns).