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Wound Healing.
Wounds
| Question | Answer |
|---|---|
| When does healing begin? What are the main methods? | Healing is initiated when inflammation begins. B. Occurs via a combination of regeneration and repair |
| What is regeneration and what are the tissue types? | Replacement of damaged tissue with native tissue; dependent on regenerative capacity of tissue B. Tissues are divided into three types based on regenerative capacity: labile, stable, and permanent. |
| What are Labile tissues? | possess stem cells that continuously cycle to regenerate the tissue. 1. Small and large bowel (stem cells in mucosal crypts, Fig. 2.5) 2. Skin (stem cells in basal layer. Fig. 2.6) 3. Bone marrow (hematopoietic stem cells) |
| What are Stable tissue? | are comprised of cells that are quiescent, but can reenter the cell cycle to regenerate tissue when necessary. 1. example is regeneration of liver by compensatory hyperplasia after partial resection. |
| What are permanent tissue? | lack significant regenerative potential (e.g., myocardium, skeletal muscle, and neurons). |
| How does the repair process start? | REPAIR A. Replacement of damaged tissue with fibrous scar B. Occurs when regenerative stem cells are lost (e.g., deep skin cut) or when a tissue lacks regenerative capacity (e.g., healing after a myocardial infarction, Fig. 2,7) |
| what is the initial phase of repair? | Granulation tissue(NOT GRANNULOMA!!!!!!) formation is the initial phase of repair-Consists of fibroblasts (deposit type 111 collagen), capillaries (provide nutrients), and myofibroblasts (contract wound) |
| What is the final step of repair? | scar formation -type 111 collagen is replaced with type 1 collagen with the help of collagenase and ZINCC 1. Type III collagen is pliable and present in granulation tissue, 2. Type I collagen has high tensile strength and is present in skin, tendons, |
| Marker for Hematopotietic stem cells? | CD34+ |
| Stem cells of the lungs are called? | type 2 pneumocytes |
| Collagen type 1 is seen in ? | bone-(has one in it) support and tensile strength |
| Collagen type 2 is seen in ? | Cartilage(car-two-lage) |
| Collagen type 3in seen in ? | RBC stretch granulation tissue embryonic tiisue |
| Collagen type 4 is seen in ? | basement membrane |
| Mechanism of regeneration and repair? | Mediated by paracrine signaling via growth factors (e.g., macrophages secrete growth factors that target fibroblasts results in gene expression and cellular growth. |
| What kind of growth factor is TGF-a? | |
| What kind of growth factor is TGF-b? | important fibroblast growth factor; also inhibits inflammation |
| What kind of growth factor is Platelet-derived growth factor—? | growth factor for endothelium, smooth muscle, and fibroblasts |
| What kind of growth factor is Fibroblast growth factor | important for angiogenesis; also mediates skeletal development |
| What is Vascular endotheliel growth factor? | Angiogenesis |
| Describe cutaneous Primary intention healing | 1. Primary intention—Wound edges are brought together (e.g., suturing of a surgical incision); leads to minimal scar formation |
| Describe cutaneous Secondary intention healing | Secondary intention—Edges are not approximated. Granulation tissue fills the defect; MYOFIBROBLASTS then CONTRACTS the wound, forming a scar. |
| What is delayed wound healing? | The patient doesnt heal in the apropriate time due to S.aureus infection, Vit C def, Malnutrtion, Cu Zn def,rupture of a wound, Access production of scar tissue. |
| Why is Vit C important in healing? | Vitamin C is an important cofactor in the hydroxvlation(adding OH) of proline and lysine procollagen residues; hvdroxylation is necessary for eventual collagen cross-linking. |
| Why is Cu important in healing? | Copper is a cofactor for lysyl oxidase, which cross-links lysine and hydroxy lysine to form stable collagen. |
| Why is Zn important in healing? | Zinc is a cofactor for collagenase, which replaces the type 111 collagen of granulation tissue with stronger type I collagen. |
| Hypertrophic scar vs a Keloid | Hypertrophic scar is excess production of scar tissue that is localized to the wound Keloid is excess production of scar tissue that is out of proportion to the wound |
| Characteristics of Keloid tissue? | 1. Characterized by excess type III collagen 2. Genetic predisposition (more common in African Americans) 3. Classically affects earlobes, face, and upper extremities |
Created by:
atayal
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