Wound contraction is mediated by –

"Perhaps the feature that most clearly differentiates primary from secondary healing is the phenomenon of wound contraction, which occurs in large surface wounds. Permanent wound contraction requires the action of myofibroblasts— altered fibroblasts that have the ultrastructural characteristics of smooth muscle cells. Contraction of these cells at the wound site decreases the gap between the dermal edges of the wound"- Robbins 7th/113 Healing By First Intention (Wounds With Opposed Edges) Robbins 7th/all-113 □ The least complicated example of wound repair is the healing of a clean, uninfected surgical incision approximated by surgical sutures. Such healing is referred to as primary union or healing by the first intention. □ The narrow incisional space immediately fills with clotted blood containing fibrin and blood cells; dehydration of the surface clot forms the well-known scab that covers the wound. □ Within 24 hours, neutrophils (Polymorphonuclear leukocytes) appear at the margins of the incision, moving toward the fibrin clot. □ In 24 to 48 hours, spurs of epithelial cells move from the wound edges (with little cell proliferation) along the cut margins of the dermis, depositing basement membrane components as they move. □ By day 3, the neutrophils have been largely replaced by macrophages. Granulation tissue progressively invades the incision space. □ By day 5, the incisional space is filled with granulation tissue. Neovascularization is maximal □ During the second week, there is continued accumulation of collagen and proliferation of fibroblasts The leukocytic infiltrate, edema, and increased vascularity have largely disappeared. □ By the end of the first month, the scar is made up of a cellular connective tissue devoid of inflammatory infiltrate, covered now by the intact epidermis.