Mod1 Phases of Wound Healing

Study Notes

Phases of Wound Healing

Healing involves a cascade of phases that partially overlap in time.

Immediate Reaction to Injury

Injured capillaries contract to minimize bleeding.
Red blood cells and platelets aggregate to form a clot.

Inflammatory Phase

Capillaries dilate, increasing permeability for serum and white blood cells.
White blood cells, including neutrophils and macrophages, migrate into the wound area.
Neutrophils and macrophages engulf dead tissue and bacteria through phagocytosis.
Inflammation subsides once all dead tissue is cleared.

Proliferation Phase

Wound is filled with granulation tissue, composed of new capillaries and connective tissue.
Angiogenesis supplies nutrients essential for granulation tissue formation.
Fibroblasts, the predominant cells in this phase, migrate and multiply at the wound site.

Wound Contraction

Specialized fibroblasts called myofibroblasts cause wound contraction to make the wound smaller.
Re-epithelialization begins when granulation tissue is nearly level with surrounding skin.

Epithelial Cell Behavior

Epithelial cells alter shape and migrate across the wound bed to cover it.
Migration ceases once cells make contact with each other, returning to their normal appearance and reattaching to the basement membrane.

Transition to Scar Tissue

Granulation tissue matures into scar tissue through reorganization and collagen fiber maturation.
Collagen fibers are oriented and cross-linked to maximize tensile strength.
Remodeling of scar tissue can take up to two years post-injury.

Phases of Wound Healing

Wound healing is a complex process consisting of overlapping phases that work together to restore tissue integrity.

Immediate Reaction to Injury

Injured capillaries constrict to limit blood loss through reduced blood flow.
Clot formation occurs as red blood cells and platelets aggregate, preventing excessive bleeding.

Inflammatory Phase

Capillary dilation increases vessel permeability, allowing serum and white blood cells to enter the wound.
Neutrophils and macrophages are the primary immune cells that infiltrate the wound, aiding in cleanup.
Phagocytosis is utilized by these cells to eliminate dead tissue and bacteria, essential for infection control.
The inflammatory response diminishes once necrotic tissue has been cleared from the wound site.

Proliferation Phase

The formation of granulation tissue marks this stage, characterized by new capillaries and connective tissue.
Angiogenesis enhances blood supply, delivering vital nutrients necessary for tissue repair.
Fibroblasts are crucial in this phase, actively migrating and creating the extracellular matrix at the site of injury.

Wound Contraction

Myofibroblasts, specialized fibroblasts, facilitate wound contraction, effectively reducing the size of the wound.
Re-epithelialization initiates as granulation tissue approaches the level of the surrounding healthy skin.

Epithelial Cell Behavior

Epithelial cells change shape and migrate to cover the wound bed, a crucial step in healing.
Cell migration halts when cells contact one another, leading to the restoration of their normal form and attachment to the basement membrane.

Transition to Scar Tissue

Granulation tissue progresses to scar tissue through a process involving reorganization and maturation of collagen fibers.
Collagen fibers are strategically aligned and cross-linked to enhance tensile strength.
The remodeling phase of scar tissue can extend for up to two years following the initial injury.

Description

Explore the critical stages involved in wound healing, including immediate reaction, inflammation, proliferation, and contraction. Each phase plays a vital role in ensuring effective healing and recovery of tissues. This quiz will test your understanding of these crucial processes.