Wound Healing Lecture Notes PDF

Definition of healing: The body’s replacement of destroyed tissue by living tissue. The healing process involves two distinct processes A- Regeneration: the replacement of lost tissue by tissues similar in type. B- Repair (healing by scaring) the replacement of lost tissue by granulation tissue whi...

Definition of healing: The body’s replacement of destroyed tissue by living tissue. The healing process involves two distinct processes A- Regeneration: the replacement of lost tissue by tissues similar in type. B- Repair (healing by scaring) the replacement of lost tissue by granulation tissue which matures to form scar tissue. Types of cells Based on their proliferative capacity there are three types of cells. 1. Labile cells which have a continuous turn over by programmed division of stem cells. They are found in the surface epithelium of the gastrointestinal tract, urinary tract or the skin. 2. Stable cells Tissues which have such type of cells have normally a much lower level of replication the cells of such tissues can undergo rapid division in response to injury.. Liver, endocrine glands and renal tubular epithelium has also such type of cells which can regenerate. 3. Permanent cells These are non-dividing cells. If lost, permanent cells cannot be replaced, For example: adult neurons, and cells of the lens. Regeneration involves two processes 1. Proliferation of surviving cells to replace lost tissue 2. Migration of surviving cells into the vacant space. The capacity of a tissue for regeneration depends on its 1) proliferative ability 2) degree of damage to stromal framework and 3) on the type and severity of the damage. b. Repair (Healing by connective tissue) Definition:- Repair is the orderly process by which lost tissue is eventually replaced by a scar. Wound contraction Wound contraction is a mechanical reduction in the size of the defect. The wound is reduced approximately by 70-80% of its original size. Contraction results in much faster healing, since only one-quarter to one-third of the amount of destroyed tissue has to be replaced. If contraction is prevented, healing is slow and a large ugly scar is formed. Wound HealThere are two patterns of wound healing depending on the amount of tissue damage: 1. Healing by first intention (Primary union) 2. Healing by second intention 1. Healing by first intention (primary unionis the healing of a clean surgical incision.The wound edges are approximated by surgical sutures. the incisional space is narrow and immediately fills with clotted blood, containing fibrin and blood cells; dehydration of the surface clot forms the well-known scab that covers the wound and seals it from the environment almost at once 2. Healing by second intention (secondary union) When there is more extensive loss of cells and tissue, such as occurs in infarction, inflammatory ulceration, abscess formation, and surface wounds that create large defects,  Factors that influence wound healing Local Factors Type, size, and location of the wound A clean, aseptic wound produced by the surgeon’s scalpel heals faster than a wound produced by blunt trauma, which exhibits aboundant necrosis and irregular edges.Small  Vascular supply. Infection Ionizing radiation Systemic Factors Circulatory status Infection Systemic infections delay wound healing.  Metabolic status Poorly controlled diabetes mellitus(impaired circulation,impaired sensation.infection) Nutritional deficiencies. Hormones Corticosteroids impair wound healing, Thyroid hormones, androgens, estrogens and growth hormone also influence wound healing.. Complications of Wound Healing 1. Infection A wound may provide the portal of entry for many organisms. Infectrion may delay healing, and if severe stop it completely. 2. Deficient Scar Formation. The complications of deficient scar formation are: a. Wound dehiscence & incitional hernias b. Ulceration 3. Excessive Scar Formation An excessive formation of collagenous tissue results in the appearance of a raised area of scar tissue called keloid tends to progress and recur after excision. It is especially frequent after burns. Hypertrophic Scar Hypertrophic scar is structurally similar to keloid. However, hypertrophic scar never gets worse after 6 months unlike keloid, which gets worse even after a year and some may even progress for 5 to 10 years. Following excision keloid recurres, whereas a hypertrophic scar does not. Stages in Fracture Healing (Bone Regeneration) Stage 1: Haematoma formation. Stage 2: Inflammation.. Stage 3: Demolition. Stage 4: Formation of granulation tissue. Stage 5: Woven bone and cartilage formation. 6: Formation of lamellar bone. 7: Remodelling.