If your skin gets punctured when you have been mucking around in the back yard or if you have undergone surgery, you are definitely familiar with the pain of a healing wound. No doubt there are some wounds that will present a grisly sight and need to be taken care of constantly. Others need nothing more than a Band-Aid and you’re good to go.
What makes these wounds so different? What is your body doing that makes one wound so unpleasant and uncomfortable and another just a minor inconvenience? We are here to find out.
NOT ALL WOUNDS HEAL THE SAME; HERE ARE THE TYPES
There are different types of wounds and depending on the circumstances that you present with, they will heal in dissimilar ways.
Primary: This is the kind of wound that requires closure or contraction and then goes ahead to heal naturally provided that you are in perfect health and there are no underlying factors to place hurdles in the healing process. The wound is closed up with sutures, skin adhesive or clips and then left to its own devices, sure that it will heal.
Secondary: Wound healing in this category is a whole other problem to deal with. This is because they edges of the wound cannot be brought together and as such the healing has to go on with the wound open. It is mainly for this reason that such kinds of wounds are prone to infection, further complicating the healing process.
Tertiary: This is also known as delayed primary. In this form of healing, the wound is observed for a few days to ensure that all the infected tissue has been excised. Subsequently, the wound can be contracted as in the primary method and left to heal. Hence the term ‘delayed primary’.
WHAT EXACTLY HAPPENS AS THE WOUND IS HEALING?
The inner workings of the healing process are complex. But since this complexity helps us enjoy life, why not go into it and take a look around. Careful, though, there are plenty of biological repairmen working feverishly down here.
First and foremost, it should be noted that the body has organized the healing process into a number of phases. This order ensures that your wound heals in an efficient and clean manner, devoid of infection. Though these stages are identifiable, they are not sequentially discrete. That is to say, there is significant overlap amongst the stages, with some starting when the other is not yet complete.
Blood is the stuff of life. When you are injured, you begin to leak this fuel upon which your life is driven. It is for this reason that the first thing your body does is to stem the flow of the blood from your body. When the platelets in the blood come into contact with the wounded area, they summon a cascade of cytokines, growth factors and other pro-inflammatory mediators. The resulting effect is that there is formation of a fibrin plug – commonly referred to as the clot – so that no more blood leaves the body.
The platelet-derived growth factor (PDGF) calls out to the neutrophils, macrophages, fibroblasts and smooth muscle cells. Transforming growth factor beta (TGF-β) summons more cytokines and monocytes. This stage lasts 4 to 6 hours.
When the blood has stopped flowing, inflammation starts to occur. During this stage, the vessels in the affected area become more permeable, allowing serous fluid to leak into the affected area. This permeability also allows monocytes to cross capillary walls and move to the injury site.
Since the skin is punctured, bacteria see this as an opportunity to launch an attack. Not if the neutrophils have anything to do with it! Their numbers in the wound build up with the primary aim of phagocytosis of such bacteria. What you see as pus is the neutrophils filled with dead bacteria.
The stream of aforementioned monocytes is then activated into macrophages which are phagocytic towards these used neutrophils and other non-viable cells, thus cleaning up the wound. The macrophages also release more growth factors, enhancing the healing process. Inflammation results in a clean wound bed, a process lasting around 3 days.
3.REGENERATION AND PROLIFERATION:
This is the longest part of the wound healing process, becoming more pronounced on the third day though starting during the period of inflammation. It can last up to a fortnight or more. The aforementioned fibroblasts are responsible for generation of the extracellular matrix. They are supported by epithelial and smooth muscle cells which are called upon chemotaxically by the PDGF and TGF-β.
Vascular endothelial growth factor (VEGF) moves to the wound site due to the low levels of oxygen known as a hypoxic environment. Formation of new capillaries occurs at the same time as the fibroblast proliferation to ensure that these cells have plenty of oxygen to work with in the development of new tissue.
The fibroblasts form collagen to cover the deficit of tissue at the injured site. In the primary wound, this is complete by day 5 or 6. In the secondary wound, granulation has to occur in a bid to fill up the gaping hole. This granulation tissue is slow to form and it needs the patient to be in peak nutritional status.
Epithelial cells contract around the wound so as to cover it up, closing it off from the outside world. In the secondary wounds, this has to wait until the gaping wound is filled up with the granulation tissue.
This stage goes on for a longer time, taking months and even years. During this period, the fibroblasts strike a balance between depositing collagen and breaking down the wound matrix with matrix metalloproteinases. At the end of it all, the final scar usually has about 80 per cent of its original tensile strength.
It should be noted that sometimes this balancing act does not quite come off, resulting in the formation of keloids and hypertrophic scars. As well as being painful at times, these kinds of abnormal scars are a blemish cosmetically.
And that is how your body deals with the various injuries that you experience. A complex process that it manages to pull off every time you have an accident or go under the knife.
Wound Healing. (2018). [image] Available at: https://woundeducators.com/phases-of-wound-healing/ [Accessed 14 Mar. 2018].
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