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UNIT 4 Supporting Physiological Function
from the existing capillaries at the edge of the wound. The result is the formation of granulation tissue, which bleeds readily and is easily damaged. As the clot or scab is dissolved, epithelial cells begin to grow into the wound from surrounding healthy tissue and seal over the wound (epithelialization). Maturation Phase—Epithelialization The final phase of the healing process, known as remodeling, begins in the second or third week and continues even after the wound has closed. During the next 3 to 6 months, the initial collagen fibers that were laid in the wound bed during the proliferative phase are broken down and remodeled into an organized struc- ture, increasing the tensile strength of the wound. How- ever, scarring can result when the keratinocytes in the epidermis (outer layer of the skin) produce too much collagen for healing. Knowledge Check 32-4 Identify the type of wound healing (primary, secondary, or tertiary intention): ■ A wound that heals from the inner layer to the surface ■ A wound with approximated edges ■ A wound that heals by approximating two surfaces of granulation tissue ■ A wound that is sutured and has minimal or no tissue loss Wound Closures Wounds that heal by primary and tertiary intention may be closed in several ways. Adhesive Strips In the following situations, adhe- sive strips are used for wound closing by: ■ Closing superficial low-tension wounds, such as skin tears or lacerations ■ Closing the skin on a wound that has been closed sub- cutaneously to aid in healing and reduce scarring ■ Giving additional support to a wound after sutures or staples have been removed Adhesive strips are often kept in place until they begin to separate from the skin on their own. For com- plete instructions, See Chapter 32, Procedure 32-9, Placing Skin Closures, in Volume 2. Sutures The traditional wound closures are sutures (“stitches”). Suturing creates small puncture wounds along the track of the laceration or incision. Several types of suture materials are available. ■ Absorbent sutures are used deep in the tissues—for example, to close an organ or anastomose (connec- tive) tissue, or with fine facial sutures. Because they are made of material that will gradually dissolve, there is no need to remove absorbent sutures.
Injury to tissue
Inflammatory phase
Occur simultaneously
Inflammation
Hemostasis
Severed vessels constrict
Release of bradykinin, histamine, serotonin, prostaglandins
Platelet and fibrin clots form
Vasodilation and increased permeability of capillaries
Contraction of clot
Migration of WBCs
Proliferative phase
Fibroblasts enter wound
Collagen synthesis
New blood and lymph vessels form
Epithelial proliferation and migration
Maturation phase
• Collagen fibers remodeled • Tensile strength increases
Contraction (shrinkage) of wound
Healing
FIGURE 32-5 Stages in the wound-healing process.
scab on the wound surface, which seals the wound and helps prevent microbial invasion. Proliferative Phase—Granulation This phase occurs from days 5 to 21. Cells develop to fill the wound defect and resurface the skin. Fibroblasts (connective tissue cells) migrate to the wound, where they form collagen, a protein substance that adds strength to the healing wound. New blood and lymph vessels sprout
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