Wound Healing/Tissue Repair

Flashcards for wound healing and tissue repair lecture review.

Wound

An injury to a living tissue that typically involves laceration or breaking of a membrane. Can be caused by physical, chemical, or microbial factors.

Tissue Repair/Healing

Restoration of tissue architecture and function after an injury; involves cell proliferation, migration, and differentiation, as well as interaction between cells and the extracellular matrix.

Regeneration

Complete restitution of lost tissue components by proliferation of residual cells and maturation of stem cells, resulting in the restoration of normal tissue structure and function.

Connective tissue deposition (scar formation)

Repair by deposition of connective tissue when injured tissues are incapable of regeneration or severely damaged, leading to scar formation and potential loss of function.

Labile tissues

Cells that proliferate throughout life, continuously replacing lost cells, e.g., epithelium of the skin and GIT. These tissues have a high regenerative capacity.

Quiescent cells (Stable tissue)

Cells with a low level of replication that can undergo rapid division in response to stimuli, e.g., parenchymal cells of the liver and kidneys. These cells are capable of regeneration under the right conditions.

Non-dividing (permanent cells)

Cells that cannot undergo mitotic division in postnatal life, e.g., neurons and cardiac muscle cells. Injury to these tissues typically results in scar formation.

Hemostasis, Inflammatory phase, Proliferative phase, Remodeling

The four phases of acute wound healing, occurring in a sequential and overlapping manner to restore tissue integrity.

REGENERATION

Replacing injured tissue with the same type of original tissue cells, occurring in tissues composed of labile and stable cells. Results in complete restoration of tissue structure and function.

REPAIR BY SCAR FORMATION

Healing when repair cannot be accomplished by regeneration alone, characterized by replacement of injured cells with connective tissue leading to scar formation, which may result in functional impairment.

Angiogenesis

Formation or development of new blood vessels from pre-existing vessels, crucial for delivering oxygen and nutrients to the healing tissue.

Granulation tissue

Hallmark of healing, characterized by proliferation of fibroblasts, new capillaries, and loose extracellular matrix, providing a framework for tissue repair.

Scar

Evolved granulation tissue composed of inactive fibroblasts, dense collagen, and fragments of elastic tissue, representing the final stage of tissue repair.

Connective tissue remodelling

Balance between ECM synthesis and degradation resulting in remodeling of the connective tissue framework, leading to increased tensile strength and improved tissue function.

EXTRACELLULAR MATRIX (ECM)

ECM regulates the proliferation, movement, and differentiation of cells by providing structural support and biochemical cues.

Interstitial Matrix

Present in spaces between cells in connective tissue and between epithelium and supportive structures, synthesized by mesenchymal cells. Provides a hydrated gel that allows for nutrient diffusion.

Basement Membrane

Organized array of interstitial matrix around epithelial cells, endothelial cells, and smooth muscle cells. Provides structural support and compartmentalizes tissues.

Growth factors

Proteins that affect cell growth by binding to specific receptors on the cell surface or intracellularly, stimulating cell proliferation, differentiation, and survival.

Epidermal growth factor (EGF)

Associated with mitogenic effects for keratinocytes and fibroblasts; stimulates keratinocyte migration; stimulates formation of granulation tissue, accelerating the wound healing process.

Healing by first intention

Healing of skin wounds where principal mechanism of repair is regeneration and the injury usually involves only the epithelial layer, resulting in minimal scarring.

Healing by second intention

Healing that occurs when there are unclean/infected wounds, irregular margins, and extensive loss of cells and tissues, resulting in more pronounced scarring and potential complications.

Haemostasis & Inflammation

Platelet adhesion and aggregation and the formation of a clot in the surface of the wound, leading to inflammation by releasing cytokines and growth factors.

Proliferation

Formation of granulation tissue, proliferation and migration of connective tissue cells, and re-epithelialization of the wound surface, restoring the barrier function of the skin.

Maturation

ECM and tissue remodelling, and wound contraction, resulting in increased tensile strength and a more organized scar.

Deficient scar formation

Inadequate formation of granulation tissue or assembly of a scar, leading to impaired wound healing and potential wound dehiscence.

KELOIDS

Grow beyond borders of the original wound, and do not go away on their own, often requiring medical intervention.

HYPERTROPHIC SCARS

Remain within the boundaries of the original wound and will spontaneously get smaller often within a year, with potential for cosmetic improvement.

FRACTURE HEALING Primary union

Direct attempt by the cortex to re-establish itself after interruption without callus formation, resulting in faster and more complete healing.

Indirect or secondary bone healing

Fracture healing that