**3. Wound healing process**

The wound healing process mainly consists of four stages: Hemostasis, inflammatory, proliferative, and remodeling [8]. The graphical representation of this sequence is shown in **Figure 5**.

• **Hemostasis:** In this phase, blood clotting causes the wound to close. The moment blood outflows the body (due cut or some other reason), this phase starts and restricts the blood flow by constricting the blood vessels. When the blood vessel's epithelial wall ruptures, the aggregation and adherence of platelets to the subendothelium surface take place within seconds. Within sixty seconds after the above event, the adherence of the first fibrin strand takes place. The blood gets converted from liquid to gel by releasing prothrombin and procoagulants when the fibrin mesh begins. The wound area contains the trapped blood cells and platelets due to the formation of thrombus or clot. Thrombus is vital in wound healing, but if it gets detached from the vessel wall and travels through the

**Figure 4.** *A photograph of a complicated wound [7].*

*Minimally Invasive Microneedle: A Novel Approach for Drug Delivery System and Infected… DOI: http://dx.doi.org/10.5772/intechopen.105771*

#### **Figure 5.**

*A diagrammatic representation of wound healing phases: Hemostasis phase, inflammatory phase, proliferative phase, and remodeling [8].*

circulatory system, it might cause strokes or pulmonary embolism [9]. The process of hemostasis is shown in **Figure 6**.


#### **Figure 6.**

*An image indicating different stages of hemostasis: vessel constriction, primary hemostasis, and fibrin clot conversion [9].*

used for repairing the wound are removed [12]. Disorganization of the collagen, which was laid down during the proliferative phase, takes place; the wound becomes thicker. The tensile strength of the healing tissue is increased by remodeling the collagen into a more organized structure along the lines of stress. Matrix metalloproteinases are secreted by fibroblasts. Type III collagen is remodeled into type I collagen by enzymes. After around 21 days of the injury has taken place, the remodeling begins and may continue for a year or more. The wound areas, which are healed, are weaker than the uninjured skin, even with cross-linking. They have only 80% of the tensile strength of healthy skin [13]. **Figure 9** is the diagrammatic representation of the remodeling phase.
