Surface wound healing - the during and after

medyouthalliance
3 days ago
4 min read

By: Monica Walters

Cuts and scrapes are something we all experience at some point. Eventually, the bleeding stops and the pain subsides. The wound shrinks, sometimes leaving a faint scar where it once was. Beyond that, the skin is almost just as it was before the painful, crimson tear - not much thought goes into how it healed itself. The healing of the skin is vital - for protection against pathogens, retaining blood and other essential fluids, and shielding against damage - but is often taken for granted. In fact, the healing of the skin is a dynamic, multi step process.

The process of wound healing is a 4 stage process:

Hemostasis
Inflammation
Proliferation
Maturation

Stage 1: Hemostasis - 2 or more days

Hemostasis is a first response to an injury.

When you get an injury like a paper cut, or scrape your knees, there is a tear in the skin and blood vessels in the dermis (the second layer) are damaged.

As a result, the blood vessels in the area constrict to reduce blood flow to the site of the injury. This vasoconstriction reduces the bleeding to minimise blood loss.
The blood is exposed to the components of exposed tissue of the blood vessel, such as collagen, which platelets in the blood bind to. This forms a platelet clot, sealing the wound.
Finally, coagulation occurs. In coagulation, the platelet plug is reinforced by fibrin, an insoluble, threadlike protein. This forms a blood clot. The fibrin forms as a result of the coagulation cascade, a complex chain reaction where one clotting factor activates the next in many steps.

Stage 2: Inflammation - 6 or more days

This stage is characterised by inflammation, redness, pain, and heat at the wound site.

Right after the injury, the injured blood vessels leak transudate (a solution made of water, salt and proteins), which causes localised swelling.
Vasodilation occurs, where the blood vessels dilate in order to prevent infection. When the blood vessels dilate, more oxygen and nutrients, as well as enzymes and white blood cells enter the wound site.
These kill pathogens and clear debris and this results in the swelling, heat, and pain commonly seen during this phase.

Stage 3: Proliferation - more than 2 weeks

This stage focuses on filling and covering the wound.

The wound contracts as new tissue is built ( Myofibroblasts cause the wound to contract by gripping the wound edges and pulling them together)
The new tissue is known as granulation tissue, designed to replace tissues that have been damaged. Granulation tissue is made up of extracellular matrix and newly formed connective tissue. Fibroblasts help create granulation tissue by synthesising and depositing proteins such as collagen. They also secrete chemicals such as vascular endothelial growth factors which helps with the formation of new blood vessels.
A new network of blood vessels is formed so that the granulation tissue can receive sufficient oxygen and nutrients for growth.
Healthy granulation tissue is pink or red and uneven in texture, and does not bleed easily.

Stage 4: Maturation - 2+ years

Collagen is remodelled and the wound fully closes.
The cells which were used to repair the wound that are no longer needed undergo apoptosis - ie. programmed cell death (eg. inflammatory cells).
Collagen is aligned and water is reabsorbed so that the collagen fibres can lie closer together and cross link.

The buildup of collagen in the granulation tissue results in new scar tissue.

Scarring:

Scar tissue primarily consists of a band of collagen fibres in a parallel pattern, which makes the scar tighter and less flexible than healthy tissue, which has a more flexible, basket weave pattern of collagen.

This is due to the rapid formation and deposition of collagen by the fibroblasts during the wound healing process.

Types of mature scars:

Atrophic - depressed, or sunken scar due to insufficient collagen formation during the healing process eg. chicken pox or acne
Linear or widespread hypertrophic - thick, raised scar due to the excess formation of collagen in the healing process eg. a surgical cut
Keloid - also thick and raised, but unlike hypertrophic scars, these extend beyond the borders of the initial injury eg. scars from burns

Excessive fibroblast activity, often occurring in large burns and severe injuries, results in hypertrophic scarring and keloid formation

Wound first aid for major cuts:

Wash hands to avoid infection
Check that there is nothing stuck in the wound. If there is, press firmly on either side of it to push the edges of the wound together.
If there is nothing in the wound, gently apply pressure on the wound with a clean cloth or bandage
Elevate the area until the bleeding stops. For wounds on the hand or arm, raise it above the head. For wounds on lower limbs, lie down and raise it above the level of the heart to reduce blood flow to the wound.
Clean the wound. Keep the wound under running water to lower the risk of infection. Wash with soap around the wound (Do not get soap in the wound, as this can irritate the wound). Remove debris or dirt with tweezers cleaned with alcohol.
Put on antibiotic ointment to prevent infection, or petrolium jelly to keep the surface moist and reduce risk of scarring.
Cover the wound. Using a bandage or gauze, cover the wound to keep it clean.
Change the covering at least once a day.