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Skin Injury Repair and Aging

Skin Injury Repair and Aging

Overview of Skin Healing Stages

  • Skin healing consists of four stages:

    • Hemostasis

    • Inflammatory phase

    • Proliferative phase

    • Remodeling phase

Hemostasis

  • Hemostasis is defined as the stopping of bleeding. It comprises three main steps:

    1. Vasoconstriction

    • Blood vessels constrict to minimize blood loss from the injured site.

    • Constriction occurs to its maximum capacity, serving to prevent excessive bleeding.

    1. Formation of a Platelet Plug

    • Small blood cells known as platelets adhere to one another with the help of a protein known as von Willebrand's factor.

    • Note: von Willebrand's factor and thromboxane A2 are not major focus areas for examination.

    1. Fibrin Formation

    • The actual clot is formed through a process called fibrin formation, which occurs after vasoconstriction and the formation of a platelet plug.

Inflammatory Phase

  • The inflammatory phase is characterized by significant degranulation of mast cells and basophils, leading to the release of crucial chemicals especially histamine. This causes:

    • Vasodilation: Expansion of blood vessels leading to increased blood flow to the injured area.

    • Exudate: Fluid exits blood vessels and enters interstitial space, leading to swelling.

  • Extravasation: Immune cells, particularly macrophages, exit blood vessels to clear out debris from the injury.

  • Four cardinal signs of inflammation influenced by histamine:

    • Redness

    • Swelling

    • Heat

    • Pain

Proliferative Phase

  • During the proliferative phase:

    • Fibroblast Migration: Fibroblasts move into the wound and produce connective tissue.

    • They create ground substance and collagen, helping to reorganize the wound area.

    • Angiogenesis: Formation of new blood vessels to supply the area with nutrients and oxygen.

    • Formation of Granulation Tissue: Characterized by a granular appearance. This tissue is not as strong or organized as the original tissue.

    • Reepithelialization: Keratinocytes migrate into the wound and proliferate, eventually covering the wound and creating a waterproof barrier.

    • At this stage, inflammation should decrease, and the initial blood clot disintegrates.

Remodeling Phase

  • In the remodeling phase:

    • Ongoing deposition of connective tissue by fibroblasts, as skin reorganizes to gain strength.

    • Potential development of Keloids: This occurs when scar tissue rises above the normal skin surface.

    • Keloids are weaker and have lower tensile strength than the original tissue despite appearing robust.

    • Moisture is a critical factor in wound healing:

    • Keeps the environment conducive for cell migration (e.g. reepithelialization and fibroblast activity).

    • Wounds that are too dry can hinder healing.

    • It's emphasized that keeping wounds covered and moist is vital to healing efficacy.

Systemic Factors Affecting Healing

  • Various systemic factors can impede wound healing:

    • Diabetes: High blood sugar contributes to delayed healing by facilitating bacterial growth.

    • Nutrition: Insufficient intake of nutrients can impair recovery due to a lack of building blocks for protein synthesis.

    • Smoking: Prolonged smoking delays the inflammatory and proliferative phases of healing.

    • Age: Advanced age often results in prolonged healing times.

    • Alcohol consumption: Also affects healing negatively.

Order of Healing Stages

  • Students are expected to know the order of the healing phases:

    1. Hemostasis

    2. Inflammation

    3. Proliferation

    4. Remodeling

  • While the exact timeline of healing can vary widely based on factors such as wound size, depth, and patient characteristics, knowing the sequence is crucial.

Burns

  • Burns can severely disrupt healing due to tissue removal, leading to dehydration and increased infection risk. Burns are categorized as:

    1. First-degree Burns: Only affect the epidermis.

    2. Second-degree Burns: Damage extends to the dermis and epidermis.

    3. Third-degree Burns: Extend down to the hypodermis with significant destruction of skin layers.

  • The Rule of Nines for assessing burn area:

    • Each limb: 9%

    • Trunk: 36% (front and back combined)

    • Each leg: 18%

    • Example calculation: A patient with severe burns to one arm (9%) and their trunk (36%) would amount to a total of 45% burned skin area.

Aging and Skin Changes

  • Aging individuals (over 65) exhibit notable skin changes:

    • Thinning of the skin with reduced layers of the stratum corneum.

    • Decreased number of Langerhans cells (macrophage function) affecting infection resistance.

    • Reduced vitamin D production, leading to potential health issues.

    • Fewer melanocytes contribute to paleness in elderly patients.

    • Diminished function of sweat and oil glands, complicating temperature regulation.

    • Less blood supply, essential for nutrient delivery and debris removal in healing.

    • Hair follicles become less active.

    • Decreased elastic fibers, leading to wrinkling.

  • Important: Clinical care for elderly patients should consider these physiological changes and their implications for wound healing.