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Wound healing is a classical example of regeneration and repair. : 

Wound healing is a classical example of regeneration and repair. It can occur in two ways : Healing by first intention(primary union) Healing by second intention(secondary union)


HEALING BY FIRST INTENTION This type of healing of a wound has the following characteristics: i) clean and uninfected ; ii) surgically incised ; iii) without much loss of cells and tissues ; and iv) edges of wounds are approximated by surgical sutures

The sequence of events in primary intention are: : 

The sequence of events in primary intention are: Initial haemorrhage . Acute inflammatory response. Epithelial changes. Organisation. Suture tracks.

Slide 5: 

1 - 2 days: epithelial basal cells grow along cut dermis 3 days: neutrophils gone, macrophages enter, granulation tissue forms 5 days: space filled with granulation tissue and collagen fibrils bridge line of closure, epidermis at pre-incision thickness Week 2: accumulation of collagen, fibroblasts, and “blanching” begins (edema and inflammation reduced) End of first month: connective tissue devoid of inflammation; epidermis intact Tensile strength increases to 70 - 80% of unwounded skin in 3 months


HEALING BY SECOND INTENTION This type of healing has the following characteristics : i) Open with a large tissue defect ,at times infected ; ii) having extensive loss of cells and tissues; and iii) The wound is not approximated by surgical sutures but is left open.

The sequence of events in second intention: : 

The sequence of events in second intention: Initial haemorrhage. Inflammatory phase. Epithelial changes. Granulation tissue formation. Wound contraction. Presence of infection.

Differences between primary and secondary union of wounds : : 

Differences between primary and secondary union of wounds :

Extracellular Matrix – wound strength : 

Extracellular Matrix – wound strength ECM provides turgor, rigidity, support, adhesion substrate, reservoir for factors It is under constant maintenance and remodeling ECM must remain intact for parenchymal healing

Extracellular Matrix : 

Extracellular Matrix Collagens Fibrous structural proteins Most abundant component of healing scars Confers tensile strength due to crosslinked structure

Extracellular Matrix : 

Extracellular Matrix Elastin: fibrillin core gives recoil to tissues such as vessel walls, uterus, skin defect in its synthesis leads to Marfan Syndrome with weakened aorta and skeletal abnormalities

Extracellular Matrix : 

Extracellular Matrix Proteoglycans and hyaluronan Hydrated gels Confer resilience and lubrication to joints (cartilage) Major importance in binding water to ECM Growth factor reservoir

Extracellular Matrix : 

Extracellular Matrix Adhesive glycoproteins and integrins Link components of the ECM to each other Links ECM to cells via surface integrins Laminin (basement membrane) and fibronectin (interstitium) are major adhesive glycoproteins

Factors Influence healing : : 

Factors Influence healing : Two types of factors influence the wound healing : Local features: Infection Poor blood supply Foreign bodies Movement Exposure to ionising radiation Exposure to ultraviolet rays Type,size and location of injury

Slide 17: 

B. Systemic features : Age Nutrition Systemic infection Administration of glucocorticoids Uncontrolled diabetes Haemotologic abnormalities

Complications of wound healing: : 

Complications of wound healing: Infection Implantation(epidermal) cyst formation Pigmentation Deficient scar formation Incisional hernia Hypertrophied scars and keloid formation Extensive contraction neoplasia

Hypertrophied scars/keloid formation : 

Hypertrophied scars/keloid formation

Wound Contraction : 

Wound Contraction

Thank you ! : 

Thank you !

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