okay in this chapter we're going to talk about skin cancer burns and some of the developmental and aging aspects of skin now we can't cover all of the disorders of skin because there's thousands that can develop but what's interesting though is that many internal diseases can reveal themselves on skin you know these might be autoimmune where the immune system can attack you know deeper tissues but they can also present in skin an example this is like lupus or other infectious diseases which are pretty common but some of the least common but also more damaging can be things like skin cancer and burns which will go into more detail in this lecture so skin cancer is can be a group of life-threatening growths of skin cells now most skin growths are just tumors which are benign and therefore not cancerous and they don't spread or metastasize however if it's cancer they're growths or tumors that that are metastatic and therefore cancerous and they're more dangerous because they can spread to many different organ systems now some of the risk factors for content cancer include things like over exposure to ultraviolet radiation and other forms of radiation you know frequent irritation of skin can also lead to cancer and some skin lotions actually contain enzymes that can repair damaged DNA which is actually pretty pretty cool because if let's say if you get a sunburn and you're worried about that the UV radiation from that sun exposure may have damaged your DNA there are lotions now that actually contain enzymes that can repair damaged DNA now there are three major types of skin cancer we'll talk about here we got the basal cell carcinomas squamous cell carcinoma in the least common but most fatal is called melanoma now basal cell carcinomas are the least malignant but also the most common and you know they're most often going to be benign growths of the skin and specifically the stratum assaleh cells proliferate and slowly invade the dermis and hypodermis they are typically easily cured by surgical excision and excision just means to cut out and this is true of 99% of basal cell cases now basal cell carcinoma is going to look like a small rounded projection with a per appearance which may be pitted and you know they're fairly common and it's considered a growth within skin and there but they're less likely to become cancerous now squamous cell carcinomas are the second most common type they also can metastasize but they're much less likely to metastasize than let's say melanoma it involves the keratinocytes of your strata spinosum hence the name squamous cell carcinoma and it's usually kind of a scaly reddened papule on the scalp you know cap yewll's are going to be small rounded projections and you can find this on the ears lower lip or hands you know because these are the areas of our face that are more often associated and exposed with to UV radiation from Sun now you get fairly good prognosis as long as it's treated by radiation therapy or surgically removed and what the squamous cell carcinoma looks like is basically this sort of reddened or arithmetic flakey scaly kind of appearance here this is probably somewhere on the scalp and you can see here this is just a pretty typical example of squamous cell now melanomas are cancers of the melanocytes member of the melanocytes make melanin now these are the consider the most dangerous type because melanocytes are more often likely to metastasize and spread throughout the body as well as be resistant to some of the drugs we had used to fight cancers like chemo therapeutic drugs now it's treated by a wide range of like surgical excision you're talking about you're going to have pretty large margins of cuts to remove that tissue that can that may contain the melanoma that also go very deep and this may be also accompanied by immunotherapy to help improves your your immune system's ability to attack these melanocytes now the key to survival for melanoma is early detection you know you want to detect these growths before they have the potential to get large enough or spread on your body and we actually use this ABCD rule a refers to a symmetry you know if the if the darkened patch of skin which you might think is a mole it has you know kind of odd or irregularly shaped boundaries and therefore a cymek circle this is not a good sign B stands for border so border irregularity means like you know if it doesn't have very clear margins if it's kind of hazy borders or exhibits indentations this is also you know one of risk factors for melanoma see refers it color so if it's by color like if it contains many different colors within that growth like if it ranges from black brown and tan or red or blue this is also not a good sign as well it's better to have you know growths that have more of a uniform color and the diameter is also something to consider so growth so let's have a diameter larger than six millimeters which is about the size of a pencil eraser you know these would need to be evaluated for the potential of melanoma so melanomas can appear like this remember we use the ABCD rule so you can see that this is much larger than six millimeters uh you obviously see that it's actually fairly dark but much darker than a mole would normally be you know has sort of it's asymmetrical in the sense that it's not you know a mirror image on each side and the boundaries are fairly clear but there are some indentations here which could also be a sign of melanoma now not all melanomas look like this sometimes melon almost just look like the tiniest little mole on your skin and sometimes melanomas aren't even dark because some melanomas don't produce melanin normally so there's still melanocytes but they don't produce the pigmented molecule melanin so that the melanoma can actually be you know just skin color now in terms of burns it's actually tissue damage caused by heat electricity radiation or chemical exposure and this is actually caused by damage that leads to denaturation of proteins which means that they are miss folded and this can also destroy cells irreversibly the most immediate threat from burns is dehydration because remember one of the major functions of skin is to prevent dehydration or water loss as well as electrolyte loss if you lack skin because of a burn then this is going to be a weeping wound that's going to lose a lot of water through dehydration and that water is going to carry electrolytes with that so that um you know individ Jules who have large burns can dehydrate or undergo electrolyte imbalances with this can lead to the shutdown of your kidneys and even lead to circulatory shock where you don't have enough blood pressure to maintain adequate blood flow to your body's organs now to evaluate burns we used something called the rule of nines now the rule of nines is more of an approximation of total body skin surface area and we can use this to estimate the volume of fluid loss that may occur in response to you know a particular burn but that we can break down the body into eleven different sections in each of these sections represents about nine percent of the body surface except for the the groin area which would be about one percent of total body skin surface area so what this lot is showing is basically just percentages of skin surface area as a as a fraction of the whole and so you can see that on the anterior you know head and neck that represents four and a half percent so the entire head and neck would be nine percent of your total body skin surface area the entire upper appendage is also nine percent however just the anterior part is four and a half percent the anterior trunk is eighteen percent so the entire trunk posterior and anterior would be thirty six percent of your skin surface area the per diem or drawing is only one percent and then each lower appendages 18% total with nine percent on the anterior and nine percent on the posterior side so we call this the rule of nines because these are typically numbers that just are divisible by nine or factors of nine and we can see that if you tally this up it leads to one hundred percent never this is more of an approximation because people's body types can vary and the proportion of skin surface area isn't going to be constant from person to person you know like on an upper appendage however gives us a very rough approximation that can help clinicians especially emergency metal medical staff to determine how much fluid loss may occur so for instance if you know that someone burned only their anterior thigh that's going to be about four and a half percent of their total body skin surface area right because if their entire thigh and leg is nine percent or lower appendage anteriorly then half of that would be four and a half percent here and we can use that number to understand well how much fluid are they going to need to maintain you know adequate blood volume so we can classify burns based on severity and we have first second third degree burns as well as a fourth degree burn first degree burns only damage the epidermis so you see localized areas of redness edema swelling and pain and we typically think about first degree burns is only damaging the epidermis right so not deeper structures so it's just more of a mild irritation of the skin second-degree burns include at the epidermis and the upper dermal areas these are the ones that are more likely to blister and can lead to first or second degree burns are referred to as partial thickness burns but these can be painful because of nerve involvement and may blister or bleed because you've damaged the dermis now third-degree burns are full thickness burns where you've gone through the entire epidermis through the whole dermis and because of this the skin is going to look kind of a grayish white or cherry red or blackened you don't find a Dima because or and also this these wounds are typically not painful because of damage to blood vessels and nerve endings and because these are so deep skin grafting is usually required and these skin grafts can come from yourself they can come from you know animal animals they can come from amniotic lining or even cadavers so what we see here there's just example of first second and third degree burns so first degree burn would just be more of a mild irritation of the epidermis so you see localized redness and swelling here second degree burns are more likely to blister and be painful because of damage to the dermis and so blood vessels are more likely to be leaky which causes your skin to blister here and then third-degree burns are deep there's a full thickness burn you can see that that they've actually the skin is burned all the way through here and you're actually looking at subcutaneous tissue this is not skin anymore because this is the skin layer here you've gone all the way through skin and this is all just subcutaneous tissue so it's considered a third-degree burn now fourth degree burn is actually going to be down into muscle and bone that's how that's classified now burns are considered critical if twenty-five percent of your body has secondary burns or if about ten percent of your body has third-degree burns it's particularly worse if it faced hands or feet have third-degree burns because of you know immobility and tribute for burns can include things like debridement which is removal of burn skin antibiotic therapy to prevent infection temporary covering which could be things like gauze or even artificial skin and maybe even skin grafts from the same individual or other animals or cadaver so other developmental aspects of the skin are just kind of interesting to talk about because you know in terms of fetal development of skin you find that the skin of the fetus is fully developed by the end of the fourth month now we have different types of words be described developmental stages like there's a lanugo coats which are just delicate hairs that develop on the fetus in the fifth and six months and then there's a vertex KC ossa which is basically a protective layer of oil that surrounds the skin of the fetus which protects the skin while the fetuses submerge within the watery amniotic environment now during infancy and childhood skin thickness and you know we'll start skin will thicken gets thicker it accumulates more sebaceous fats as well as sweat and glands can increase now in terms of you know during teenage years you can see things like the development of acne do to increase activity of sebaceous glands skin is optimal appearance during the twenties and thirties but after age 30 you know the effects of killin of environmental assaults start to show on skin so that you know wrinkles show and skin can become thinner or you see more localized area of damage with moles or freckles also as we age you know scaling and dermatitis become more common as well now in terms of aging effects on skin we see that epidermal replacement slows so that the skin actually becomes thinner um it can be drier and itchy because decrease in sebaceous gland activity and subcutaneous fat and elasticity also start to decrease so these find that individuals are more cold and tolerant and they have more wrinkles here there's an increased risk of skin cancer due to the lifetime and a cumulative effects of UV exposure and there's also hair thinning throughout skin these are all important considerations because if you think about how if skins are less of a protective barrier and elderly and they're more prone to you know injury so because their skin is weaker now the ways ways to delay skin aging are to have adequate UV protection you know good nutrition maintaining adequate fluid and good hygiene over the course of your lifetime