Stage 1: HemostasisHemostasis or haemostasis occurs immediately after theinjury. When our skin breaks our body’s first response is vasoconstriction.Vasoconstriction is when our blood vessels constrict to decrease the amount ofblood leaving. This happens because of direct injury to smooth muscles,chemicals released by endothelial cells and platelets and by reflexes initiatedby nearby pain receptors. Platelets flow in our blood and have 2 main receptors: glycoprotein1b(GP1b) andglycoprotein2b3a(GP2b3a). There is another glycoprotein found in our bloodcalled the von Willebrand factor(VWF).
When this binds to the GP1b receptor andthe subendothelial collagen the platelet is activated. In platelets there are 2 granules called densegranule and alpha granule. In these granules there are differentsubstances called fibrinogen, VWF, serotonin, adenosine diphosphate (ADP), andcalcium.
These substances are released into the blood through degranulation.When combined with thromboxaneA2 they lead to more platelets aggregating whichcreates a platelet plug. Finally fibrinogen found in our blood changes tofibrin through the coagulation cascade. Fibrin creates a mesh on top of theplatelet plug making it stronger.
Figure 1: Hemostasis http://physiologyplus.com/describe-the-three-steps-of-hemostasisStage 2: Inflammation When the skin is injured our body sends out chemokines,chemical messengers, into the interstitial fluid which is located under ourskin but above the endothelial cells. The chemokines, a type of cytokine, tellthe body something is happening. The bacterium surrounding our cut comes intothe body and may send out its own byproducts into the bloodstream. Thesebyproducts or the chemokines can activate the mast cells in our skin.
The mastcells when activated will release histamine, an inflammatory mediator.Histamine goes to the endothelial cells and cause vasodilation in thecapillaries. The capillaries are now filling up with fluid. When this happensthe endothelial cells move apart letting the blood flow through. The bacteriabyproducts as well as the chemokines enter into the blood vessel. Neutrophils,a type of white blood cell, are attracted to these chemicals. They want to getclose to them which they achieve by margination and extravasation.
Marginationis when the neutrophils adhere to the endothelial cells. Extravasation ordiapedesis is when the neutrophils start to leave the blood vessel through thegaps between the endothelial cells. The whole point of this is so that the neutrophilscan get to the pathogens and go through phagocytosis. Phagocytosis will enablethem to ‘eat’ up the bacteria, the debris and any damaged cells. Dendriticcells, another cell in our skin, B-cells, T-cells, macrophages and otherphagocytes help get rid of the bacteria just like the neutrophils.
Through this process our body gives off heat, becomes red,starts to swell and hurt which are called inflammatory responses. Rednessoccurs because the capillaries are filled up with more fluid than normal.Swelling happens because of the increase in fluid. More blood comes to the areabecause of vasodilation which makes our skin hot.
The cut often gives us painbecause the body releases chemicals that fuel nerve endings making the areasensitive. Figure 2:Inflammation process https://www.slideshare.net/pramodkuamarpamu/acute-inflammation-40385817Stage 3: ProliferationThe proliferation or granulation stage is when the woundcloses and can from 4 to 24 days.
Fibroblasts and myofibroblasts proliferate inthe wound and end up making the extracellular matrix. Then the myofibroblastsattach to the fibronectin and collagen in the extracellular matrix and start topull which contracts the wound by bringing the sides of the wound closer. Anyredundant fibroblasts are taken away through apoptosis, in other words aplanned cell death. Collagen is made from fibroblast and is especiallyimportant in this stage as well as maturation. Blood vessels need an optimalsupply of oxygen and nutrients for the granulation tissue to be made. Thegranulation tissue is made of extracellular matrix and collagen which lets thegranulation tissue to develop a new web of blood vessels to take over for thedamaged ones. This process I called angiogenesis.
The colour of the granulationtissue can tell us if the process is going smoothly. If it is pink or red thatmeans the tissue is healthy but if it is dark it could mean there is aninfection, a poor delivery of blood also known as perfusion or a stoppage ofblood which is known as ischemia. The body changes damaged mesenchymal cellsinto fibroblasts to help cells move around.
They secrete collagen and liquidswhich helps to strengthen the wound. The wound continues to grow stronger asthe fibroblasts help in the formation of new tissue and accelerate the healingprocess. The epithelial cells come to surface of the wound and close the wound.
If there is a scab in the way then this process will take much longer than itshould. Figure 3: Collagen and fibroblast at the wound in theproliferation stage https://tbtri2dc00482337.wordpress.com/about/Stage 4: MaturationMaturation or remodeling is the last stage inthe healing process and transpires after the wound is closed. This stage canlast months even years. It is responsible for the formation of new epitheliumand scar tissue. In this stage the new granulation tissue made in theproliferative stage becomes stronger and flexible. The collagen fibers reorganizewhereas the tissue remodels and matures.
Any cells left that are of no useanymore are removed by apoptosis. The amount of blood vessels in the injuredarea decreases as they leave the area. In the proliferative stage the collagenis all over the place and disorganized. In this stage collagen type III, themain material in granulation tissue, is replaced with collagen type I, the maincomponent in the dermis. The collagen now aligns itself with the tension linesand water is absorbed which lets the collagen fibers lie next to each other andcross link. The intramolecular and intermolecular cross links of collagenresults in an increased wound bursting strength.
Wound bursting strength is theamount of pressure needed to break the wound. The final scar reaches only 80%of its original tensile strength. Infection Infectionhappens when bacteria, viruses, or other microbes enter our body and star tomultiply.
Disease happens when the cells in our body are damaged and signs ofan illness appear. A lot of the symptoms we suffer through when we are infectedare caused by our immune system fighting off the infection. White blood cells,antibodies and other microbes get rid of the pathogen. The immune system maycause the following symptoms in order to help fight off the infection: fever,headache, rash or malaise. Viruses have nucleic acid in them, DNA or RNA, which issurrounded by a protein shells and sometimes lipids.
They cannot reproduce ontheir own so when it enters a host cell it uses the host’s metabolic system tomake copies of itself. These copies can come out of infected cells or a cellmembrane. They make us sick by killing cells and disrupting their cellfunction. Most of the time our body will respond with a fever; a feverinactivates viruses.
The body will also secrete interferon, a chemical thatstops viruses from reproducing. Another way our body might stop a virus is bysending all the antibodies to the pathogen.Bacteria are single celled organisms that can either help usor hurt us.
They carry DNA which programs the genes needed to reproduce andother functions. Sometimes they also have plasmids which encode for specializedfunctions like antibiotic resistance. Bacteria can only carry one set ofchromosomes.
They reproduce by splitting into two cells through binary fission.The offspring are clones with the same genetic material. If a mistake were tooccur during replication a mutation can happen. It would create variety in thepopulation that could lead to the ability to adapt in a changing environment.Bacteria can evolve rapidly and suddenly when they take genetic material fromother bacteria, viruses, plants and even yeast.
Bacteria have learned how toadhere to cells, make toxins that hurt other cells, avoid or restrain ourdefenses and resist not only drugs but our immune system’s antibodies. Somebacteria reproduce so quickly that they crowd our tissues and interrupt normalfunctions. They can kill cells and tissues. The toxins they create can paralyze,destroy a cells metabolic system, or form an immune reaction that is toic.Bacteria can be in our body without causing an infection butthe chance of infection increases when there is a break in the skin. A commonexample of a bacterial skin infection would be cellulitis. Cellulitis can causeskin to swell, turn red and become warm; three out of the four inflammatoryresponses.
It can happen anywhere on your body and forms deep in our skin. Itssymptoms range from fever, numbness, infection near our eyes or ears toswelling, bruising, and a sense of coldness. Cellulitis is typically caused byeither Streptococcus pyogenes (strep) or Staphylococcus aureus (staph). It canappear by itself or a result from an infected wound.
The only way cellulitiscan spread is if the infected person comes in contact with another person andthe bacteria enter through a cut in their skin. Another bacterial skininfection that is easy to catch due to its symptoms is impetigo. Impetigostarts off as red spots and progresses to itchy blisters, normally around thenose or mouth. Impetigo is easily given to another person by skin contact orcontact with anything the infected person touched.
It can be caused bystaphylococcus or streptococcus.Wound CareWounds only start the healing process if they reach thedermis. The dermis is underneath the epidermis. The epidermis consists ofhardened cells called keratinocytes and melanocytes. Melanocytes make melaninwhich gives us the colour in our skin. Our skin colour varies not because darkskinned people have more melanocytes but because they have more activatedmelanin.
The epidermis is constantly losing dead skin cells and making new onesmaking it easy to repair. The epidermis is the body’s first shield. The dermis is also known as the corium.
It consists of livingtissue and connective tissue. Living tissue refers to blood and lymph vessels,nerve fibers as well as oil and sweat glands. Connective tissue alludes tofibroblasts, histocytes and mast cells. Fibroblast cells help repair injuriesto the skin. Histocytes protect the body by surrounding foreign substances.Mast cells contain histamine, a substance that can also be released inallergies which leads to itching.
Fibers in the dermis are made of collagen.Collagen means glue and it tough but flexible. It is a fibrous proteinsubstance found in the bone, cartilage, tendons and ligaments.
Collagen fiberssupport and protect the blood and nerves in the dermis. The nerve endings inthe dermis can sense hot, cold, pain, pressure and touch. Overall the dermishelps control infection and gives us sensation.Often times when people get cut they reach for rubbingalcohol or hydrogen peroxide to clean the wound but what they don’t realize isthat they are doing more damage than helping our skin. Disinfectants likerubbing alcohol, hydrogen peroxide, iodine and sodium hypochlorite do clean thewound but also kill off many healthy cells. In addition to killing off cellsthese disinfectants often burn when in contact with our injury. They don’t actuallyburn you but the chemicals in them activate a cell called vanilloidreceptor-1(VR1 or TRPV1). VR1 is a nerve receptor that tells us when somethingis hot.
When exposed to alcohol the alcohol molecules actually lower thetemperature needed to send the signal to the brain. Studies show that ethanolreduces the threshold temperature by 10 degrees. There are 2 theories as to whyour wound still burns if the alcohol lowers the temperature threshold butneither is confirmed. Either the heat made from our cells through theinflammatory response causes the burning or our own body temperature activatesthe VR1. Because of this our cut now hurts and feels like it’s on fire.
Aspokesperson from American Association of Dermatology, Robert Kirsner, toldReader’s Digest that these disinfectants kill off healthy cells and clean thewound. He also stated “The most effective way to get rid of debris and bacteriawithout damaging healthy tissue is flushing the wound out with water.” Mostpeople who don’t have any disinfectants will clean the wound with water andsoap.
The addition of soap isn’t as great as people think. You don’t know howour body will react with the chemicals in the soap. They might help, they mightnot. It’s better to stick with just water.Many factors can affect the healing process.
Temperaturecontrols the rate of chemical and enzymatic process happening in the injury. Italso controls the metabolism of cells and tissue working in the process.Changing the wounds many times or cleaning the wound with room temperaturesolutions decreases the temperature of the wound. It takes hours to recover tothe needed physiological levels. Therefore, wound dressings giving a “cooling”effect are not really helping. If the wound is on a bony prominence, areas ofless vascularity and in areas with thicker skin usually take longer to heal.
Linear wounds heal faster than square or rectangle ones and circular woundstake the longest to heal. If the wound is too dry a scab forms which gets inway of epithelialization. If the wound is to wet it becomes macerated.Maceration can make the wound bigger and increase the risk of infection.
Debris, necrotic tissue and foreign bodiesincrease the risk of infection which is why they need to be taken out in theinflammatory stage. Too much pressure on the wound can compromise the bloodflow and the healing process cannot happen. Anti-inflammatory medication getsin the way of the inflammation process.
Infection also slows the healingprocess. Oxygen is needed for better healing.Moist Wound HealingIn 1962 Dr. George D. Winter from the University of Londondid an experiment that changed wound healing for the better. He wonderedwhether letting the wound dry out was the best method of repairing it. Hecreated many wound on the backs of pigs.
He left some of the wounds to dry outand covered the others with polymer film. The wounds covered with polymer filmepithelialized 2 times faster than the wounds left on their own. Winterhypothesized that epithelial cells in dry wounds had to find a way to get pastthe scab which wasted time and energy while in the moist wounds they moveeasily across a moist, vascular wound surface. His hypothesis is supported bymany studies. Most of our body is made of water and the natural environment ofa cell is moist which means that if a cell were to dry up it would be a deadcell.
Moist wound healing decreases dehydration, cell death and pain. Itincreases angiogenesis and re-epithelialization. It has a lower chance ofinfection and less scarring. Moist wound healing allows epithelial cells tomigrate through the wound exudates to close the wound. Wound DressingsA dressing has direct contact with the wound whereas a bandage holds abandage in place. Dressings help the wound heal, prevent infections, stopbleeding, absorb excess blood, plasma or any other liquids, and begin thehealing process. There is a variety of dressings each with their uniquecharacteristics. Hydrocolloid dressings are used on pressure and venous ulcers, burns,necrotic wounds and under compression wraps.
They are self-adhesive,non-breathable, provide thermal insulation and create moist condition whichtriggers moist wound healing. A hydrocolloid surface is coated withpolysaccharides and other polymers which absorb water and form a gel, protectthe wound from infection, keep it clean and help heal the wound faster. Theyare impermeable to bacteria making them effective in defending the wound frominfection. Hydrocolloids are easy to use, last long and are environmental. Hydrogel can be used on an assortment of wounds that are leaking a smallamount of fluid or no fluid, are painful or necrotic wounds, pressure ulcers,donor sites, second degree burns and infected wounds.
They are designed tocomfort the patient and reduce their pain while still aiding in the healingprocess and fighting infection. The cooling gel in them is what makes themsuccessful at decreasing pain and speeding up the process. Hydrogels are mainlywater or glycerin based dressings available in sheets, gels or gauzes. Hydrogelsaren’t effective bacteria shields since they let gas and water pass through.Hydrogels like hydrocolloids provide a moist environment for the wound torepair in. Alginates dressings need to be changed every 2 days because of theamount of liquid they absorb and the nature of the wound. If you change thedressings a lot it can result in dryness which can lead to bacteria penetratingthe wound.
They should only be used for wounds with a lot of liquid drainageotherwise they can damage healing by drying the wounds too quickly. They aremade from sodium and seaweed fibers which allow them to absorb high amounts ofliquid and they are biodegradable after use. Foam dressings absorb exudates which creates an environment that helpsspeed up the healing process. They let water vapor to enter which keeps theinjury moist but prevent bacteria from entering. These dressing can be adhesiveand non-adhesive.
Foam dressings are foamed polymer solutions with small’pockets’ that can hold fluids. They can be layered in a mixture with othermaterials. They are used for partial and complete thickness wounds.
Collagen act as a crutch for new cells to grow and can be reallysuccessful when it comes to healing. They help remove dead tissue, help in theproliferation stage, and speed up the process. As you can see wound dressingscan be a great help to our body.
ConclusionOur body works hard to finish the healing process as best as they can.They have many obstacles in their way that may be caused by us or pathogensthat have entered. Add to the fact that not many people know the right way toclean a wound, it makes our bodies’ work much harder than it has to be.
Learning how the healing process works, the right way to clean a wound, whichdressing to use and why, and what infections could be in our body can make abig difference.