Wound healing is the process that the skin goes through as it repairs damage from wounds. There are three main types of wound healing, depending on treatment and wound type. These are called primary, secondary, and tertiary wound healing.
Every wound goes through various stages of healing, depending on the type of wound and its severity. Understanding these categories, as well as the steps of the wound healing process, can help people understand how best to care for a wound.
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Primary wound healing, or primary intention wound healing, refers to when doctors close a wound using staples, stitches, glues, or other forms of wound-closing processes.
Closing a wound in this way reduces the tissue lost and allows the body to focus on closing and healing a smaller-area wound rather than the larger initial wound.
For example, a doctor might stitch up a large cut rather than allow the body to heal over the entire cut.
Secondary wound healing, or secondary intention wound healing, occurs when a wound that cannot be stitched causes a large amount of tissue loss. Doctors will leave the wound to heal naturally in these cases.
This may be more common for wounds that have a rounder edge, cover uneven surfaces, or are on surfaces of the body where movement makes stitches or other closure methods impossible.
Secondary wound healing relies on the body’s own healing mechanisms. This process takes longer, which may be due to increased wound size, the risk of infection and contamination, and other factors, such as the use of certain medications.
Tertiary wound healing, or healing by delayed primary closure, occurs when there is a need to delay the wound-closing process.
This could be necessary if a doctor fears that they may trap infectious germs in a wound by closing it. In these cases, they may allow the wound to drain or wait for the effects of other therapies to take place before closing the wound.
There are several types of wounds, depending on factors such as the source of the wound and any underlying issues that may lead to it. The type may alter how doctors treat the wound or other factors in the healing process.
Wounds are typically open or closed. A closed wound is an injury that does not break the surface of the skin but causes damage to the underlying tissues. A bruise is a common example of this. On the other hand, open wounds break the surface of the skin and may also damage underlying tissues.
Some types of open wounds include:
- Abrasions: These form as a result of rubbing or scraping the skin against a hard surface.
- Lacerations: These are deeper cuts caused by sharp objects, such as a knife, or sharp edges.
- Punctures: These are small yet deep holes caused by a long, pointed object, such as a nail.
- Burns: These result from contact with an open flame, a strong heat source, severe cold, certain chemicals, or electricity.
- Avulsions: This refers to the partial or complete tearing away of skin and tissues.
Chronic wounds may also cause breakages in the skin that need to heal. These include bedsores, other pressure injuries, and diabetes-related ulcers.
All wounds go through different healing processes, ranging from the initial wound reaction to the later stages of creating new skin.
Simple wounds, such as those without extensive tissue damage or infection, take about 4–6 weeks to heal. This does not include scar tissue, however, which takes longer to form and heal.
Scar tissue will never return to 100% strength, but it will reach about 80% strength around 11–14 weeks after sustaining the initial wound.
The following sections describe the wound healing process in more detail.
The hemostasis phase occurs as the injury happens and is the first response from the body. The wound causes blood and other fluids to leave the body. The body responds by trying to stop this flow of blood.
Affected blood vessels constrict to reduce blood flow. As
This newly formed clot also prevents germs from getting into the body. This restores the skin’s function as a barrier against dirt and other potentially infectious agents so that healing can begin.
The platelets release chemicals that alert the surrounding cells to start the next process and heal the wound.
During the inflammatory phase, the cleaning and healing of the area begin.
There is generally some inflammation in the area, as the immune cells rush to the damaged tissue. White blood cells enter the area to start cleaning out the wound and move any waste away from the site and out of the body.
The proliferative phase of wound healing occurs when the wound is stable. The body’s focus during this stage is to close the wound, create new tissue, and repair any damaged blood vessels in the area.
This occurs over the course of four different processes:
- Epithelialization: This is the process of creating new skin tissue in the various layers of damaged skin.
- Angiogenesis: This is the creation of new blood vessels in the area of the wound healing.
- Collagen formation: This is the building up of strength in the tissue of the wound.
- Contraction: This is the reduction and eventual closing of the wound size and area.
The combined connective tissue and blood vessels is called granulation tissue. This granulation tissue starts to form around
During the remodeling phase, the internal wound is mostly healed. The process switches to creating strong skin to replace the temporary tissue in the area.
Some research notes that this process occurs around
The body replaces the temporary granular tissue from the early wound with stronger scar tissue. As time goes on, the scar tissue has an increased concentration of collagen, which makes it stronger.
Treatment and home care options for a wound will vary greatly based on a number of factors, such as the location of the wound, the type of wound, and any additional treatments that are necessary.
Treatments may include any closures needed, antibiotics to protect the wound, and dressings, in addition to other forms of therapy.
Doctors will give people regular instructions on caring for their wound as it heals, as well as regular dates for check-ups to help monitor the healing process.
Anyone who is uncertain about the severity or type of wound or the need for treatment should contact a doctor.
Minor wounds, such as scrapes and small cuts, may not require a visit to the doctor. However, anyone who experiences a larger wound or a wound that does not stop bleeding after the application of gentle pressure should contact a doctor for a full diagnosis and treatment.
Wounds that cover larger areas of the skin, such as road rash, may also require professional medical attention. These require proper cleaning to prevent contamination and infection.
Anyone who notices symptoms of infection — such as itching, pain, and redness around the wound — should also contact a doctor.
Wound healing is a complex process with many stages, from the moment the initial wound occurs, through the various initial reactions of the body, to the process of healing itself.
The three main types of wound healing are primary, secondary, and tertiary.
Minor wounds go through the stages of wound healing fairly quickly. More severe wounds will take longer to heal.
Any symptoms of infection, as well as any major injuries, should prompt a visit to a doctor for a full diagnosis and treatment. Anyone who is unsure about their wound healing should also contact a doctor.