Skin Injury and Repair

Skin Injury and Repair Four Stages in Skin Healing Inflammation Blood flow increases Phagocytes attracted Scab formation Cell division and migration Scar formation

Skin Injury and Repair Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response. Epidermis Dermis After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and more of these cells are arriving with the enhanced circulation in the area. Clotting around the edges of the affected area partially isolates the region. Sweat gland Scab Macrophages and fibroblasts Migratory epithelial cells Granulation tissue

Skin Injury and Repair One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating. Fibroblasts After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis. Scar tissue

Skin Injury and Repair Table 5-1

Aging of the Skin Major Age-Related Changes Injury and infection increase Immune cells decrease Sun protection diminishes Skin becomes dry, scaly Hair thins, grays Sagging, wrinkles occur Heat loss decreases Repair slows

Effects of UV Radiation Beneficial effect - activates synthesis of vitamin D3 Harmful effects Sun burn Wrinkles, premature aging Malignant melanoma Basal cell carcinoma

Types and Growth of Hair Vellus hairs Body hairs of women and children Terminal hairs Hair of scalp Axillary and pubic area (at puberty) Hair thinning and baldness Due to aging Male pattern baldness

Burns Classified by severity First-degree burn – only upper epidermis is damaged Second-degree burn – upper part of dermis is also damaged Blisters appear Skin heals with little scarring Third-degree burn Consume thickness of skin Burned area appears white, red, or blackened

Rule of Nines Assesses the percentage of burn Used to guide treatment Determines transfer to a burn unit Different for Adult and children

Estimating Burns Using the Rule of Nines Figure 5.11a

Skin Cancer Basal cell carcinoma Squamous cell carcinoma Melanoma Least malignant and most common Squamous cell carcinoma Arises from keratinocytes of stratum spinosum Melanoma A cancer of melanocytes The most dangerous type of skin cancer

Skin Cancer Squamous cell carcinoma Basal cell carcinoma Melanoma Figure 5.12