Wound Healing[1]
When skin is injured, there are four phases of wound healing that take place: hemostasis, inflammatory, proliferative, and maturation. See Figure 5.11[2] for an illustration of these phases of wound healing.
To illustrate the phases of wound healing, imagine that you accidentally cut your finger with a knife as you were slicing an apple. Immediately after the injury occurs, blood vessels constrict, and clotting factors are activated. This is referred to as the hemostasis phase. Clotting factors form clots that stop the bleeding and act as a barrier to prevent bacterial contamination. Platelets release growth factors that alert various cells to start the repair process at the wound location. The hemostasis phase lasts up to 60 minutes, depending on the severity of the injury.
After the hemostasis phase, the inflammatory phase begins. Vasodilation occurs so that white blood cells in the bloodstream can move into the wound to start cleaning the wound bed. The inflammatory process appears to the observer as swelling, redness, and drainage.
The proliferative phase begins within a few days after the injury and includes four important processes: epithelialization, angiogenesis, collagen formation, and contraction. Epithelialization refers to the development of new epidermis and granulation tissue. Granulation tissue is new connective tissue with new, fragile, thin-walled capillaries. Collagen is formed to provide strength and integrity to the wound. At the end of the proliferation phase, the wound begins to contract in size
Capillaries begin to develop within the wound 24 hours after injury during a process called angiogenesis. These capillaries bring more oxygen and nutrients to the wound for healing. When performing dressing changes, it is essential for the nurse to protect this granulation tissue and the associated new capillaries. Healthy granulation tissue appears pink due to the new capillary formation. It is also moist, painless to the touch, and may appear “bumpy.” Conversely, unhealthy granulation tissue is dark red and painful. It bleeds easily with minimal contact and may be covered by shiny white or yellow fibrous tissue referred to as a biofilm that must be removed because it impedes healing.
During the maturation phase, collagen continues to be created to strengthen the wound. Collagen contributes strength to the wound to prevent it from reopening. A wound typically heals within 4-5 weeks and often leaves behind a scar. The scar tissue is initially firm, red, and slightly raised from the excess collagen deposition. Over time, the scar begins to soften, flatten, and become pale in about nine months.
- This work is a derivative of Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., Kruse, D. H., Korol, O., Johnson, J. E., Womble, M., & DeSaix, P. (2022). Anatomy and Physiology 2e. OpenStax. https://openstax.org/books/anatomy-and-physiology-2e/pages/1-introduction ↵
- “417 Tissue Repair.jpg” by OpenStax College is licensed under CC BY 3.0 ↵
The initial phase of wound healing, where clotting occurs to stop bleeding.
The second phase of wound healing, where the body fights infection and clears debris.
The third phase of wound healing, where new tissue forms to replace the wound.
The process by which new skin cells cover a wound.
New connective tissue and tiny blood vessels that form during wound healing.
The formation of new blood vessels, essential for wound healing.
The final phase of wound healing, where collagen strengthens and scars form.
