Transcript for:
Overview of the Integumentary System

all right guys welcome this is going to be part one of the chapter five integumentary system packet all right so one thing that i like to do right in my spare time and i have a lot of spare time now uh is shopping online okay and i've kind of toned down um since uh since i was younger right nowadays i have a little bit more responsibilities and mortgages and stuff like that and you got to be kind of uh careful with your money but one thing i used to do way back in the day is okay just go on amazon and right click on deals of the day and lightning deals and you know see what you can like purchase right you can buy online so let's say you're shopping right and one of the descriptions for these lightning deals on amazon okay is for a jacket right and the description says that it's waterproof it's stretchable you can wash it so if it gets dirty right and it's permanent pressed it doesn't wrinkle okay so so far so good now it also says on the description that it can automatically repair any type of damage okay rips and burns also right it has a lifetime guarantee so for this right you know let's say you click on it it says you have to add it to your cart to see the price okay you're trying to figure out well is this expensive or is this going to be something cheap well typically if you have to put in the cart right it's something that's going to be kind of up there and this is a priceless item okay and everyone right now listening to this lecture okay you all have the jacket that's waterproof stretchable washable permanent press automatically repairs small rips and burns and it has a lifetime guarantee okay and that is your integumentary system all right so what exactly is your integumentary system well it's your skin okay so coming into this class if you're gonna ask someone okay if your skin was an organ what would you say well some of you may say no okay organs are things like your heart right and your lungs and your liver and your stomach those are organs well we just we already defined what an organ is okay and we know that an organ is a group of tissues right okay so a little bit of epithelial tissue working with a little bit of connective tissue working with okay muscle tissue working with nervous tissue so if we have a structure that has tissues woven together right we start to make the next level in our hierarchy which is known as an organ all right so if i look at tissues tissues are made up of epithelial tissue tissues are made up of connective tissue right they have nervous tissue they have muscle tissue so actually all four tissue types come together to make this organ called the skin okay and is your skin considered an organ of course it is it is right for someone not taking anatomy right someone has no idea okay what a tissue is okay they're going to say no tissue is not a tissue is not an organ okay your heart's in oregon your stomach's an organ well if it has more than one tissue working together it's an organ okay so if i ask you later on is a blood vessel an organ well you better say yes or you're not learning anything so it is the largest organ actually of the entire human body it counts for seven percent of our total body weight okay and our skin varies in thickness okay it could be thin about one and a half millimeters in thickness for example think about maybe the skin on your forearm right or we think about thicker skin okay okay about four millimeters in thickness like on the palms of your hands were on the soles of your feet now by this time okay we've we've already discussed okay the skin in lab right when we talked about the tissue lab and hey we talked about epithelial tissue and connective tissue simple squamous and stratified squamous and the different types of connective tissue like areolar and cartilage and stuff like that okay so this is not something that's unfamiliar to you guys you guys should be pretty much comfortable with this stuff right so as we're going through this lecture okay you already know some of this stuff okay but what we're gonna do is we're gonna now start adding a little bit more complexity to the picture okay that's in your head right now so we're gonna get a lot more detail okay and just remember guys when we test you on skin okay in lab it only pertains to the information that you guys learned in your lab manual and in that video presentation that i did for you right when i talk about skin in terms of testing on a midterm in lecture well then it's going to be a little bit more complex why because okay i'm giving you a lot more detail in this video all right so we do test the two separately but again you always can take what you learned from lecture to help you with your lab exams and vice versa you can also always take the stuff that you learn in lab okay and apply it to the material that you're learning now in lecture okay all right so what's the first thing you should always do when you're looking at either a picture of skin a diagram of skin a model of skin or even a slide of skin what's the first thing that you should always do well the first thing you should always do okay is look for the wavy boundary okay and here i see this wavy boundary so what's the significance of that wavy boundary well above the wavy boundary is what we call my epidermis all right and this is what well this is your epithelial tissue this is a thick stratified squamous epithelium okay on the apical side you see these flat squamous cells now below the wavy boundary to the part where you see start seeing lots of fat well then what's this well this is the connective tissue that supports my stratified squamous on the basal side so this is the apical side of my epithelium this is the basal side method why because this is connective tissue and the name we give this connective tissue from the wavy boundary to the point where i start seeing lots of fat tissue we call this part of your skin this is the dermis okay so we're going to talk about the dermis it has areolar connective tissue in here it has dense irregular connective tissue that makes up the dermis okay now on the very bottom here this is not part of your skin right we learned this in lab this is called the hypodermis right and hypodermis is primarily made up of fat tissue adipose tissue okay but we're going to see that it also has some areolar present in here all right so the job of the hypodermis okay it's it shares many of the functions of the skin but it's not part of the skin okay we're going to see that the hypodermis is going to anchor your skin okay to underlying structures particularly to the muscles that are down deep in your body alright so your skin is only what your skin is only the epidermis which is a stratified squamous epithelium okay and the dermis which is a mixture of areolar and dense irregular connective tissue okay now when i say always look for the way boundary there is a wavy boundary between the dermis and the epidermis okay and one of the functions that we're going to see is that it holds the two layers tightly to one another okay you never want your epidermis separating from your dermis and if that happens what would we call that we call that a blister okay so if you ever had a blister right in your lifetime what happened there was that your epidermis separated from your dermis okay very painful all right so again you have thick skin in your body and you have thin skin in your body ranging in point from one and a half millimeters in very thin skin it's around four millimeters in thickness okay and thicker parts of your body right so the function okay the main one you can think about is protection right because when i think about that epidermis being a stratified squamous okay well that's that's the thickest epithelium we have that's going to separate two environments right we don't use a simple epithelium right to make your epidermis we're going to use multiple layers of sauce so protection is going to be one what are some other functions well it screens out harmful uv rays from the sun okay in lab we learned that the very bottom of the layer bottom layer of your dermis called the stratum basal right it has cells called melanocytes okay those melanocytes make a pigment called melanin okay and that melanin then okay shields right the nuclei of our cells right from harmful uv rays okay because uv light can do what well uv light can cause cancer all right now uv light isn't all bad though right it's good that you go outside sometimes why because uv light also stimulates the production of vitamin d in your skin right and what does vitamin d do well it helps you uptake calcium from your diet okay so for the build up okay of healthy strong bones right you're gonna need you have to have your kids play outside okay you can't keep them all day okay at home indoors okay so by being outside okay you get uv light okay your skin produces vitamin d vitamin d then allows your body to uptake calcium okay and calcium is needed okay for many processes and one of them is the healthy growth and development of our bones and our skeleton all right what's another function of your skin well it insulates and cushes cushions underlying body tissues okay because we're gonna we're gonna see guys right we don't want heat okay in many cases dissipating away from our body on a cold day we don't want okay okay too much heat to be retained right on a warm day so we have this ability okay in terms of heat regulation right it protects our body from water loss our skin is waterproof okay we don't want water just evaporating from our body transpiring from our body right okay if water does evaporate because we secrete it onto the surface of our skin in the form of sweat all right it helps regulate body temperature okay there are blood vessels okay present within right your um your skin so we think of things like vasodilation and vasoconstriction okay so let's play a little thing we're gonna we actually have to use your brain right now right on a cold day okay before i even do that okay is is your blood hot okay does your blood retain heat and the answer is yes right it's made up of water and water is a good okay conductor of heat so on a cold day would you want this hot blood all right reaching your skin reaching the surface of your body on a on a very uh let's say hot or cold let's just do for far i forgot what i said on a cold day would you want this hot blood reaching the surface of your body on a cold day well no because you want to keep yourself warm on a cold day so i'm not going to get my warm blood onto this on some surface of my body so that i lose this warmth that i lose it to the outside environment so on a cold day you actually have what's called vasoconstriction okay you actually limit the amount of blood that reaches your skin so that hot blood remains at the core of your body okay which raises your body temperature right so if you ever notice on a cold day you may look pale right so okay so again if you're a lighter skinned individual you're going to notice that you're you're paler and the reason why is because there's less blood going to your skin your body doesn't want that heat to be released to the environment it wants to keep that hot blood okay at your core okay and it's just the opposite for a hot day okay you want that hot blood to reach your skin so that you can release that heat to the outside environment thereby cooling you down all right so much like okay a car uses coolant for example and it brings that hot coolant to the surface where it gets cooled down and then goes back into the hot engine okay to regulate then the temperature of the engine right so much like that we want to get that hot blood away from our body so that we then okay dissipate it to the environment and then we bring a cooler blood back to our core all right so thermal regulation okay regulating body temperature is another function all right and then excretes wastes right so things like urea and salt all right you're gonna then secrete also through your sweat so we have sweat glands that then fill to your blood right or they take products okay from your blood that are waste products and excretes it to the outside environment all right so without getting uh too specific when i was back in college right um my first two years were kind of a blur because you know i partied a little bit too much all right and there be might be some days where right i wasn't feeling too good the next morning right but one thing i did a lot was was run right and for those of you that run a lot okay this thing called the runner's high it's very hard to miss a day of running right because if you don't run that day just feels wrong okay you don't feel good at all um so after a night of having fun right um and waking up not so hot the next morning you know i still had to run okay and what do you think it smelled like right in terms of my stuff the sweat coming out of my body okay when i'm running well it smells a lot like you know whatever beverages okay i might have been consuming the night before all right so your your sweat basically is a waste product okay yes it's made up mostly of water which allows you then to cool down because of evaporative cooling okay but we can think of our integumentary system okay um in the fact that it also is involved in excreting waste all right and then contain sense organs so we know that we have the ability in our skin to sense like you know pain temperature vibration touch all right so there has to be receptors present in our skin that allow us then to sense those specific stimuli okay all right so what we're going to do is we're going to go above the wavy boundary okay so we're going to talk about this structure called the epidermis means on the skin okay and we know this from lab and notice from the introduction that we had in the first couple slides okay is that your epidermis again is a stratified squamous epithelium so here we see in this figure here is my wavy boundary right here okay and above that wavy boundary well this must be my epidermis and then this pink stuff below my wavy boundary okay well then this must be a portion of my dermis my connective tissue so this is the apical side of my stratified squamous epithelium this must then be the basal side of my stratified squamous epithelium now in lab okay we only talked about right melanocytes okay we actually can see them they're these gray cells right here right but in addition to melanocytes there's a lot more cells that make up your epidermis right and there's actually four distinct cell types okay and the one that's the most abundant of the four is listed here on the slide they're called kerotinocytes okay so everything you see yellow in this figure okay so these yellow ones right here and all these yellow ones here these flat yellow ones with purple vesicles in their cytoplasm those are keratinocytes and these very flat yellow cells all the way at the very apical side of your epithelium of your epidermis are also keratinocytes okay so all these yellow cells even with the purple vesicles those are all keratinocytes all right and they're connected together okay by desmosomes okay and we talked about these these these structures that hold then the epithelial cells to one another okay so why do we call them carotenocytes well because they make it very tough a very fibrous protein called keratin all right so keratin was what what what makes your epidermis very strong right so we talked about protection as being kind of the main function right of your skin what what makes your skin so strong is that your epidermis is what we call a keratinized stratified squamous epithelium okay as opposed to okay inside of your mouth lining your oral cavity that's that's that's the stratified squamous epithelium too because there is a brain abrasion in your mouth okay but it's it's a non-keratinized stratified squamous okay the type of abrasion that's happening on the surface of your body versus inside your oral cavity okay two different types of abrasion right falling off your skateboard versus okay chewing okay on some captain crunch right how can you compare that kind of abrasion to one another so your skin is a keratinized stratified squamous and where does that keratin come from it comes from all these yellow cells we call keratinocytes okay in addition to producing keratin keratin also produces antibiotics okay kills bacteria enzymes that help detoxify harmful chemicals okay that may come in contact with your skin all right the second cell type that we're going to see found within your epidermis are found strictly okay within the stratum basil again we'll talk about this in in lecture but in lab we know that the stratum basal is a single layer of cells closest to the wavy boundary clay closest to the dermis okay so we know that the yellow ones in the stratum base or those are the keratinocytes well these star-shaped cells here and here in gray well the then these represent all right the melanocytes all right and melanocytes they don't make keratin right they make a brown black pigment called melanin all right and melanin okay is then transferred to the neighboring keratinocyte so let's say this melanocyte makes melanin okay it then transfers the melanin to the neighboring keratinocyte okay and actually you can see it here these three okay kind of grayish dots okay and then here's another melanocyte transferring melanin to the neighboring yellow keratinocytes okay now once the melanin reaches right the keratinocytes it clusters on the superficial side of the keratinocyte okay so notice i don't see keratin down here on the basal side i don't see keratin really much on the lateral sides of my keratinocyte i see then the the melanin okay clustered on the superficial side of my keratinocytes okay so why is that important why doesn't why is it important okay that melanin is on the superficial side all right so if we go to our our little pseudo white board here and i just draw for example here is a melanocyte okay that makes melanin and then right next to it is this keratinocyte right and here's another keratinocyte over here well why does the melanin cluster on the superficial side okay why isn't it like down here and over here and over here well it's because where is the uv light coming from right so this is the apical side so uv light right is coming from this direction all right and uv light yes it could be beneficial produces okay helps produce vitamin d but uv light can be very harmful harmful to what harmful to the dna that's present in the nuclei of my cells so by having the melanin cluster on the superficial side of my keratinocytes what are you effectively doing effectively you are now blocking the uv light from hitting the dna okay that's present inside of this nucleus all right and dna again okay it's a nucleic acid composed of okay adenines thymine cytosine and guanis okay and uv light can mutate this dna sequence so if i mutate my dna well then what happens well then you mess up the rna which then what happens well then messes up the messenger rna which then what happens well then messes up proteins okay so if you mess up proteins well then what happens possibly to the cell okay for example what happens okay to a protein involved in the cell cycle right g1 s g2 okay mitosis and cytokinesis what if i mess up a gene involved right or a protein involved in checkpoint control what's going to happen now well now you have uncontrolled cell division okay you start producing now cancer cells okay you might now have skin cancer because of that exposure to uv light so by having the melanin cluster on the superficial side you are effectively creating an umbrella shielding then the dna from that ionizing radiation all right so that's why it's important that it clusters on the superficial side all right that's what we can see here for example right and that's what these these grayish bluish dots represent now in our population okay we have individuals that may be darker skin we might have individuals that might be lighter skinned individuals right so what's the difference okay between let's say a darker skinned individual and a lighter skinned individual okay is it mean then well lighter skin individuals have less melanocytes in the stratum basal that's why they're lighter skin okay or okay darker skin people have more melanocytes in the stratum basil than a lighter skinned individual right that's why they're darker well that's not true okay the number of melanocytes you see in a lighter skin person okay is pretty much equal to the amount of melanocytes you see in a darker skin person okay and the only difference is what well it's the genetics involved right it's genetics that tell the lysosomes within these keratinocytes whether or not to intracellularly digest the melanin so if your genetic says well digest the melanin so here's let's say a lysosome okay that's present right inside of this keratinocyte okay if the genetic says we'll digest the melanin well then what's going to happen then well you're going to then digest the melanin right well what if your genetic says well melanocyte do not touch the melanin right so here is a melanocyte a lysosome okay lysosome do not touch the melanin well then what's gonna happen well you're not gonna digest the melanin melanin will persist persistent in higher levels of your epidermis and that's what we see for example okay in this figure here right we see that this would be a figure of a lighter skin person or a darker skin person well i only see now okay only these deeper layers of keratinocytes having melanin on their superficial side if i look at the next layer of keratinocytes okay i don't see any melanin okay why because okay this individual's genetics okay is telling their lysosomes to intracellularly digest the the melanin so this person doesn't have very much melanin in their skin well they're going to have a lighter complexion okay as opposed to if this was a darker skin person i would expect to see more umbrellas in higher levels of this individual's epidermis okay so the amount of melanocytes in a lighter skin person the amount of melanocytes in a darker skin person is pretty much the same okay the amount of melon in though the amount of pigment actually is the is the difference there right at the third cell type we're going to talk about is found strictly also in the stratum basil so i i find keratinocytes in my stratum basil i find melanocytes in my stratum basil and you also find these purple hemisphere shaped cells okay purple in the figure obviously okay we call these merkle cells right it always reminds me okay of family matters did i do that okay i think it's sterical right so what do these merkle cells do well they're the receptors for touch right so when you push pressure on your skin when you press pressure on something it's these merkle cells that then okay receive that stimuli and then send that information okay to a sensory nerve ending okay which is part of your nervous system all right so these are the receptors for touch okay only found again within the stratum basal of your epidermis okay and the fourth cell type okay we see here found strictly within the stratum spinosum of your epidermis okay and it's this bluish colored cell here we call this a longer hans cell right and a longer han cell is like a is a macrophage like cells so what do macrophages like to do for us again well they like to go around phagocytosing things or more specifically these longer han cells use receptor mediated endocytosis you guys recall that when we're doing the cell in the plasma membrane okay so here we're going to bind to something on a receptor on the surface of our longer han cell which is going to then trigger that longer hunt cell to then phagocytose whatever it is all right now the longer hot cell distance doesn't stay there it now leaves the spinosum and enters the dermis right ultimately okay it enters a lymph capillary and then finds a lymph node and presents then whatever found out in the skin it presents it then to killer t lymphocytes which are called killer t cells okay which is one of the cells involved in your immune response so the reason why let's say you're immune to something is because okay of these memory lymphocytes all right so it found something here in the spinosum it leaves it enters your dermis it finds a lymph node okay and it says all right does this belong to anybody i found it in the skin right and then there's a killer t-cell that says oh that was mine yeah we got sick from that okay when we're in kindergarten all right and that killer t lymphocyte divides by mitosis divides divides divides divides and then it spreads out through the entire body looking then for more of these things to kill okay so that you don't get sick from it a second time around all right okay so this next part here we're going to talk about the different layers right of your epidermis because we know it is a stratified squamous epithelium it's not just a single layer cells it's multiple layers of cells all right so here's my wavy boundary down here again so single layer of cells closest to a boundary okay consisting of keratinocytes in yellow okay melanocytes in gray and merkle cells okay hemisphere shell cell cells okay in in purple what we call that single layer of cells we call this shadow basal okay several cell layers thick right consisting of keratinocytes in yellow and longer han cells in blue okay we call that layer of your epidermis we call this the stratum spinosum right and we have a layer of flat cells notice the cells go from being cuboidal and they start getting more squamous now right and here we see some flat squamous cells okay one to five cell layers thick consisting of purple vesicles granules in their cytoplasm and that's why we call this granulosum okay we call this the stratum granulosum here okay and then the thickest layer of our epidermis right multiple layers of cells thick they're very very flat squamous cells now right we call this the stratum corneum all right so you can see why your epidermis now is a stratified squamous because okay on the apical side we see that we see very flat squamous cells in our stratum corneum there all right so here is a micrograph guys of thick skin so this is either the palms of your hands or the soles of your feet right four millimeters thick in the thickest regions so the first thing you always do is find a wave boundary so there's my wavy boundary right there okay so below my wavy boundary and this white color okay this must be my connective tissue this must be my dermis right and then above my wavy boundary pretty much in pink or purple okay all this on top represents then right my epidermis my stratified squamous my keratinized stratified squamous epithelium okay and as you can see in this figure they labeled here's my dermis in gray okay and this little boxing gray here well then this represents my stratum basil right there okay so from that to then we got really dark right here well this is called the stratum spanosum right and then i failed to mention this guys okay but here's my stratum granulosum with all these vesicles in their cytoplasm right granules in the cytoplasm right so when you actually take skin and you stain it right these cells of the stratum granulosum they stain very very very darkly on an actual slide right so if you're looking for the stratum granulosum look for something that's very darkly staining so if i go back to here okay here's my stratum spinosum and then right above that very darkly staining this line right there well that is my stratum granulosum all right and then here lucidum means clear so right above that you see this lighter pink color as opposed to this darker pink up here okay this is the stratum lucidum right and one thing to note about the lucidum is you only find it in thick skin okay which is in the palms your hands and shoulders your feet okay you don't find lucidum pretty much anywhere else on the body right so in thinner skin this is the layer that is absent you don't you do not have a lucidum in thin skin you only have it in thick which is the palms your hands and the soles of your feet okay so from the lucidum okay we then enter the thickest layer consisting of flat squamous cells flat keratinocytes we call that top layer there that is known as the stratum corneum okay so again if you fall off and scrape your arm you're probably losing these top layers okay of your epidermis here all right so stratum basal can single layer cells again closest to the wavy boundary consisting of keratinocytes melanocytes and miracle cells right so down here guys these are the young's remember there's keratinocytes all up and down the thickness of your epidermis the youngest keratinocytes okay are the ones in the shadow and basil okay and the ones in the stratum basil are actually stem cells these are the youngest ones and they divide okay to replace all of the ones that are lost in the top layers of your epidermis so how do i replace cells that are lost aged effective and old well we use a process of cell division involving mitosis around right so the ones down here these keratinocytes have a very okay high amount of cell division occurring okay remember you guys remember what was one of the unique qualities of an epidermis okay one of them was a high regenerative capacity okay to replace cells that are lost right so the reason why an epithelium in this case the epidermis has such a high regenerative capacity is because that the cells here the keratinocytes in yellow okay divide very rapidly they are stem cells now keep in mind all right when these stem cells divide okay both of the daughter cells they don't leave the basal and both enter the stratum spinosum okay one of the daughter cells actually stays behind why well to maintain the stem cell lineage right so if both daughter cells were to leave well then you're going to start losing right stem cells so if i go and and draw you a picture here right so here is my wavy boundary right and let's say here is a keratinocyte a stem cell okay if this stem cell were to divide to form two daughter cells and both daughter cells enter the stratum spinosum well then what happens to this stem cell that was down here well then this is now babae right so if both daughter cells exit right and enter the spinosum well then you just lost a stem cell in your stratum basal your one step stem cell less than before so instead of both daughter cells exiting okay and entering right the spinosum what happens is that one of the daughter cells okay exits and enters the spinosum okay but the other daughter cell stays behind and remains to be a stem cell in the stratum basal so in that case we do not then decrease the number of stem cells within our stratum basal okay by having one of the daughter cells stay behind all right so here's a micrograph guys of thick skin so again there's my wavy boundary so this must be my dermis down here all right so a single layer of cells in dark purple closest to the wavy boundary okay well that single layer of cells okay this would be here we'd be called the stratum basal okay so if we were to zoom in okay single layer of cells closest to the wavy boundary there would be my stratum basal okay all right so the spinosum is several cellular stick you guys you can see this figure okay towards the bottom the cells are more cuboidal but as we get closer to the granulosum you can see the cells starting to get more squamous and more flat all right so mitosis actually still occurs here it's not just in the basal okay but let's say this is one of the daughter cells this one actually will divide again to form two daughter cells these two daughter cells will divide again to form four daughter cells so forth and so on okay but the amount of mitosis that occurs in the spinosum is a lot less than the amount of mitosis that occurs okay within the basal okay so a lot more cell division occurring here than in the spinosum here okay now one thing we always describe our epidermis as was a keratinized stratified squamous okay why because these keratinocytes within their cytoplasm have a very tough fibrous protein called keratin right well here's the first step in making that keratin so in my spinosum i'm only going to focus on these yellow cells and they're not the blue long or han cells okay but in the cytoplasm of all of these keratinocytes in yellow okay we have thick bundles of intermediate filaments called tonofilaments right so i don't even tell you what these tonal filaments do because you should know what intermediate filaments do right so we we talked about areolar connective tissue being the most prototypical connected tissue okay and in that it has different fibers right well we're not talking about the fibers like collagen fibers elastic fibers and reticular fibers okay that those are the fibers that are outside and in between the cells we're talking about the cytoskeleton though so we're going back even another chapter into the cell chapter chapter two in that it has a cytoskeleton it has microtubules it has microfilaments and it has intermediate filaments do you guys remember what intermediate filaments do okay in the cytoplasm of a cell well these help resist tension so what do you think tonal filaments bundles of intermediate filaments do within the cytoplasm of these keratinocytes well they help resist tension okay all right so moving up okay we're gonna go from the stratum spinosum okay up here now into the stratum granulosum so this is around one to five cell layers thick here we're showing maybe one two three maybe four cell layer stick in this figure all right notice that the keratinocytes are really flat now okay they're very squamous at this point okay and inside their cytoplasm right they have a nucleus right or inside the cell they have a nucleus and inside their cytoplasm they have these vesicles okay these granules okay that are present in there that's why we call this the stratum granulosum okay so what exactly what kind of what are these granules what do these vesicles contain within these keratinocytes well there's two different types of vesicles granules contained in the cytoplasm of these cells you have what are called keratohiline granules and you have what are called lamellated granules right so what's the difference between a keratohi line and a lamellae well let's do the love mella did first well these granules contain a waterproofing glycolipid that is exocytosed into the extracellular space and plays a role in slowing in the loss of water all right so if i go okay to my pseudo white board over here okay and i'm gonna draw you guys some flattened cells in my stratum granulosum all right so here's a keratinocyte and here's a keratinocyte and so forth and so on right and what are these keratinocytes secreting right they're secreting a waterproofing glycolipid right and that waterproofing glycolipid is secreted outside and in between my cells so what does that help prevent happening okay in terms of your skin well it makes your skin now waterproof right it helps slow down water loss from your body so these lamellae granules okay contain a waterproofing glycolipid now in addition to those lumelated granules you also have what are called carotohyline granules present in the cytoplasm of these cells and these keratohyline granules right form keratin in the higher strata okay my best way to explain this is that they have a glue contained inside of them right and this glue from the keratohylan granules okay they mix with the tonofilaments inside the cytoplasm these bundles of intermediate filaments that are found inside of these keratinocytes so if i take the glue from the keratohyalin granules and i mix them then okay with those tonal filaments those bundles of intermediate filaments will then you form something called keratin right so that's why okay we say that this is a keratinized stratified squamous these more superficial layers okay are very strong okay so that what so that any type of abrasion okay anything that happens out here outside on the surface body okay we protect from it all right one important thing to note is that okay cells in the stratum basal are alive cells within the spinosum are alive and cells within the granulosum are alive okay any cells that are above that for example cells in the lucidum okay which we don't see in this figure cells in the corneum which we do see in this figure okay those cells are already dead all right so why are the cells in the lucidum not shown and the cells in the corneum die why do they die well you don't want cells that that are going to be put okay to the test and the crap that we put our skin to okay we don't want those cells to be alive okay they're gonna be dead by the time they reach the apical surface of our epidermis all right so if you're scratching something the skin starts coming off of you right the skins aren't the cells aren't coming off your body going why'd you scratch me off i was still alive right the cells up here are dead already okay now why are they dead why are cells in the lucidum and why are cells in the corneum dead well what's another characteristics guys of an epithelium besides high regenerative capacity well another characteristic is that what they are a vascular notice in this figure i don't see any capillaries here i don't see any blood vessels in my epidermis well because your epidermis is an epithelium there are no blood vessels in an epithelium so where do these cells get their blood from do you think these cells do you think these melanocytes need blood do you think these miracle cells need blood do you think these keratinocytes need blood yeah they knew they need blood but what they don't get it from the epithelium they get it down here from the dermist remember your dermis is a connective tissue and generally speaking connective tissues are very well vascularized so down here i see lots of capillaries so why are cells up here in the lucidum dead and up here in the corneum dead well because they're too far from the blood vessels that are down here in your dermis okay and we'll leave it at that now when we go to when we go to physiology you gotta you have to know functions okay now you have to really explain why cells in the lucidum and the cells in the cornea die because they're too far away from the blood vessels well you're going to say this okay as the distance of diffusion increases the rate of diffusion decreases right so the farther you have to diffuse okay the rate of diffusion starts to slow down okay so by the time we reach the lucidum by the time we reach the corneum right the cells don't get the nutrients they need to from the blood to survive okay which is technically a good thing we don't want the cells on the outer surface of our epidermis to be still alive okay all right so again the lucidum is not present here okay it only occurs in the palms of your hands and the soles of your feet okay we'll talk about thick skin okay consists of a few rows of flat dead keratinocytes okay lucida means clear okay so here's an actual micrograph of thick skin here so here's my wavy boundary okay we know that a single layer of purple dark purple cells closest would be my spot and basil okay we then know all of these cells here in that same color as the basal is the spinosum and then we see this dark layer of cells well i told you guys whenever you see the granulosum under scope this is the darkest layer okay well there's your granulosum and then right above that you see this thin pink layer above that well that there is the stratum luciano okay so concentrate on this part here's your spinosum the darkest layer is going to be the granulosum and then this clear layer right on top here okay is the lucidum okay so this must be thick skin this has got to be a picture of the palms of the hands or the soles of the feet here right so the thickest layer of your epidermis is actually your stratum corneum all right so we see lots of flat dead keratinocytes at this point okay the cells are dead their nuclei have disintegrated all their organelles are gone and disintegrated okay so what are they basically well they're basically okay thicken sacs a plasma membrane filled with keratin okay we have flat dead sacs okay filled with keratin in your stratum corneum which is very protective at that point okay so it helps protect against abrasion and also penetration all right so if i go back to this pre actually let me see if it's here okay it's right here look how thick this is okay from here to here there's your lucidum so look how thick this stratum corneum is in the palms of your hands and the soles of your feet pretty thick okay that's really really good for protection right there all right so how much skin does a person shed in his or her lifetime okay are we talking about grams right are we talking about pounds tons what are we talking about here about 40 pounds right so you shed about 40 pounds of skin in your lifetime every time you scratch an itch okay there's skin coming off of you right so it's always good okay to clean your house and vacuum because a lot of that stuff that dust and stuff that's a lot of skin just floating in the air all right same thing with your with your sheets okay it's good to wash your sheets all right if you don't have a mattress protector okay it's going to be good okay to change your mattress sometimes because in addition to that skin you also have sweat and oils that seep down into your mattress all right so here again this is spinosum dark layers of granulosum clear layers lucidum and then pretty thick layer on top would be the corneum there all right so that's your epidermis that's above the wavy boundary okay it's a very thick stratified keratinized stratified squamous epithelium all right so we're gonna talk about below the wavy boundary now so below this wave boundary to a point where i start seeing lots of fat okay i call this here this must be my connective tissue well then this here represents my dermis okay and your dermis is your body's hide right if you talk about an animal's hide okay that's what we use to make leather products so if you have a leather okay couch or a leather interior in your car or a leather belt right getting all fancy you got some leather pants or something like that well you're you're basically wearing the dermis of whatever animal was used to make that product okay and the best way i can describe the hide right is what kind of holds everything together all right so if i'm thinking about getting a hot dog all right i go on la brea and go to pinks for example right what holds all that meat that's been ground up into a hot dog like shape right is the casing so it's much like the casing that kind of holds everything inside of our body together basically all right now the dermis again is on the basal side of your epithelium of your epidermis right okay so what do we find okay underlying most epithelial tissues what's the name of that connective tissue that underlines almost all epithelial tissues again there's waiting well it's called aerial or connective tissue right so underlying our epidermis is going to be an areolar connective tissue so what's that well it's the prototypical connective tissue it has different kinds of cells right it has all three types of fibers and because of that it has four functions number one it binds and supports why it's because the matrix because of these fibers two it holds body fluid why because of this clear ground substance that holds onto this thing called interstitial fluid that leaks out of your capillaries three it fights against infection why because it has things called macrophages and mast cells and lymphocytes and plasma cells right and four it stores the energy in the form of fat why because it has adipose cells adipocytes fat cells okay so when we think about what your dermis is mana well right underneath that epidermis right underneath that wavy boundary we're talking about an areolar connective tissue okay again richly supplied with blood vessels and nerves connective tissues are very well vascularized okay and the reason why cells in the lucidum cells and corneum dies because they're too far from these blood vessels that are present in the dermis all right so if i look here okay here's my wavy boundary someone has a blister because i separated my epidermis from my dermis right but here is my dermis okay and here's lots of fat here's a lot of adipose well then this must represent okay the hypodermis which is not part of skin which we'll talk about later on so here to here must be my dermis all right now notice your dermis has blood vessels it has capillaries right and there's two different okay networks of blood vessels present within your dermis you have one that is very deep right at the boundary between the dermis and the hypodermis okay this deeper one here we call this the cutaneous plexus this is going to supply blood to the deeper regions of your dermis it's also going to supply blood okay to the hypodermis now we also have okay a network of blood vessels converging and diverging blood vessels underneath the wavy boundary right so right at that interface between your dermis and your epidermis what we call this the sub papillary plexus okay and this is going to supply blood what to the superficial regions of your dermis okay it's this subpapillary plexus then that supplies then the blood to the overlying epidermis so cells in the basal cells and the spinosum cells in the granulosum get their blood from this subpapillary plexus and the reason why cells in the lucidum and cells in the corneum die is because they're too far from that subpapillary plexus all right so why do we call sub papillary sub means below so below papilla well these finger like projections here are called dermal papilla okay the reason why there's a wavy boundary between your dermis and your epidermis is because of these finger like projections right here called dermal papilla and we'll get to them later right so sub papillary plexus right underneath those dermal papilla all right now here's where skin is involved in regulating your body temperature okay why it's involved in thermoregulation well we talked about it okay i'm not going to reiterate very much but what on a hot day you're going to have vasodilation you're going to bring blood to the surface of your body by by by now causing these to have now more blood flow so that that hot blood and the heat that's contained in them okay is then able to dissipate away from your body whereas on a cold day we're not gonna have very much blood going here we're gonna have more vasoconstriction right we're still gonna have blood but not as much blood so that what we keep that hot blood in our core we don't bring that hot blood to the surface our body and we lose the heat okay we keep it in our body on a cold day all right so unlike your epidermis which has four to five layers four to five strata we only have really two layers in your paper in your dermis okay and your dermis has two layers a papillary layer which is a superficial 20 percent and something called the reticular reticular layer which is the deeper 80 percent of the dermis right so around 20 let's say is around here right so the superficial 20 percent okay is what we call the papillary layer so why do we call papillary well the same reason why we call these the subpapillary plexus in terms of the blood vessels okay the papillary layer has the dermal papilla it has these finger like projections which is the junction between the dermis and the overlying epidermis right so what what function do these dermal pathways provide why do i need a wavy boundary between my dermis and my epidermis why can't i just have a straight boundary between the two all right so why do i need dermal pablo so why do i see something okay where i see something like this where this is my epidermis on top and this is my dermis on the bottom why do i need why do i need a weight rebounder why can't i just have this you know a straight boundary between my epidermis and my dermis well for one okay by having the wavy boundary there's more surface area right remember what's down here okay you have the subpapular plexus you have blood vessels so by having a wavy boundary you have more interaction between the dermis and epidermis you can exchange way more nutrients between the two different layers okay as opposed to having just the straight boundary here okay we wouldn't actually when you call these sub pepperoni plexus more because there's no dermal papilla okay you have less surface area less interaction okay you don't exchange as much okay between right the dermis and the epidermis now another reason why guys okay you would have actually okay a wavy boundary as opposed to a straight boundary would be what well by having now a wavy boundary what happens here okay is that now you interlock the epidermis and the dermis better with one okay again more it's kind of kind of the same reason why okay you have wavy contours between epithelial cells instead of just having epithelial cells that are one right next to the other okay you have wavy contours okay that now lock the epithelial cells tight to one another so same thing here okay you now lock the dermis and the epidermis tighter together by having a wavy boundary it again fits more like pieces of a puzzle right its heart would be harder to rip the epidermis and dermis away here than it would here okay this person would have a lot less blisters than this person over here which would have probably suffering from blisters okay his or her life because you keep separating the epidermis and the and the dermis from one another all right so that's the function of the dermal papilla alright so on the palms of your hands and the soles of your feet okay look at your fingers right now you have what are called fingerprints no the technical term we call them epidermal ridges okay so fingerprints you look at your toes you have little okay uh footprints right toe prints okay so the reason okay why do we have these here okay where do they come from well here's my wavy boundary so i know that this must be my epidermis okay and this must be my dermis down here okay so the reason why you have these these epidermal ridges so here's an epidermal ridge this would be a fingerprint for example okay so the reason why you have that is because down below it okay you have now the dermis pushing up and when the dermis pushes up it causes the epidermis on top of it to push up okay and that pushing up from the dermis we call that a dermal ridge okay so the dermal ridges push up which then cause epidermal ridges which cause for example your fingerprints so why do i need fingerprints okay why do i need these epidermal ridges on my hands and on my feet well they allow you to grip things okay so much like when you look at your tires your tires aren't smooth right your tires have ridges in them look at the bottom of your of your tennis shoes right they're not smooth okay the bottom retention shoes have ridges on them they have tread okay and that tread in your tires and your fingerprints your epidermal ridges allow you to increase friction they allow you to now grip objects okay your tires grip the road okay your shoes grip the ground well then your epidermal ridges help you grip either your feet grips the floor or your hands okay and your fingers to help grip objects now here's a picture okay of okay some epidermal ridges and what you notice are these openings right at the crest of each epidermal ridge well that's the opening of a sweat gland so here's a sweat gland here's the duct and the duct blend leaches then to these sweat pores here okay so the sweat pores are right at the crest or the peak of each one of these epidermal ridges so whenever you do what whenever you touch an object all right so if you have a you have a glass right now okay we want to touch your computer screen and look to see what's left behind well you're going to see okay an exact copy of your epidermal ridges you're going to leave behind what's called a fingerprint right well the reason why something's up behind because okay of the sweat then okay is then leave okay or left i'm sorry to leave that's not a word okay is left okay in the exact same pattern okay as your okay fingerprints so it's because of this anatomical development okay a lot of people are incarcerated okay they leave fingerprints behind all right so below that super superficial 20 the popular layer deeper parts of your dermis we call the reticular layer okay and again we've heard the word reticular a lot okay we endoplasmic reticulum for example okay rough er smooth er we've heard of reticular fibers network of fibers so the word reticular means network so the question is network of what if i'm calling this a reticular layer of my dermis well it's a network of something well it's a network of collagen fibers okay it is not reticular connective tissue so what we find in that deeper 80 what we find in the reticular layer of your dermis because the superficial 20 is areolar the deeper 80 percent is dense irregular so now we have collagen fibers pointed in different directions different orientations do you guys remember what can what what can dense irregular do very well okay that dense regular cannot do well because dense regular has all the collagen fibers oriented in a single direction dense regular like your tendons and ligaments can only resist tension from a single direction or orientation okay by having now collagen fibers pointed like this and like this and like this and coming out your computer screen and going behind your computer screen now we can now resist tension from multiple directions okay is that isn't that what you want your skin to do okay your skin isn't always subjected to only one type of pulling force right your skin is subjected to multiple okay directions and orientations of pulling force okay so right if you're going laterally okay so take your your hand right now and go to your form the skin in your forearm okay and slide back and forth right so now okay we're resisting tension okay in this horizontal plane okay we'll now take your your hand okay and kind of go forward and back on your forum okay now we're resisting okay tension okay it's still in the horizontal plane but now in a different direction now rarely do you what okay does something grab your skin and pull out like a dog bites you and pull outward okay or if i'm going shopping with my wife and she sees something she likes so she just grabs my arm and pulls in that direction right that kind of rarely happens so dense irregular the fibers point in different directions but the majority of the fibers point where in your reticular layer do they are they oriented to the parallel to the surface your skin or are they oriented perpendicular to the surface of your skin well the majority of the collagen fibers in the dense irregular okay are oriented parallel to the surface skin okay because that's typically the way okay we resist tension in our skin okay very rarely again do we have things grab our skin and pull out all right okay now in your dermis and you have collagen fibers we just saw that right now okay you also have elastic fibers so if you stretch your skin okay well then we have collagen fibers to help resist that pulling for us but if we let go we then have elastic fibers that help nail snap back into shape okay our skin has elasticity because of these elastic fibers now there may be instances where you gain some weight okay maybe you're you're bulking up right you're building muscles right it could be that okay you're not exercising you're overeating right it could be that okay you're having a baby in any case okay yours your body has to stretch okay that hide that casing that holds everything together it has to stretch so as we're expounding outward what's happening here is what well we have collagen fibers that are helping resist that tension but the second that what the second that okay we lose weight we then have elastic fibers that help snap our skin back into shape now if we gain weight okay and we get to the point where we can now break and snap collagen fibers well then what's going to happen well then you damage your dermis okay so extreme stretch stretching the skin can tear the collagen fibers in your dermis okay and if you tear the collagen fibers of dermis you create what are called stria okay these streaks okay we call stretch marks okay so we just finished talking about the epidermis which is above the wavy boundary okay and the dermis okay up to the fat down here okay so all this okay which is below the weight boundary which is the dermis okay are we done talking about the skin the answer is yes okay your skin is only composed of a dermis and an epidermis okay period the hypodermis which it means below the skin hypo is below okay is not part of your skin all right it's closely associated with your skin though that's why we typically talk about it so it has other names in addition to hypodermis okay and the way you can tell it is because you start seeing lots of adipose tissue okay so your hypodermis is main made up mainly of adipose you also have some areolar present down here okay so this would be areolar okay all this kind of boring stuff and white would be adipose okay now the reason why we talk about your hypodermis when we talk about skin is because it's closely associated okay it does what what anchors your skin okay to underline structures it anchors your skin to muscles right now besides anchoring your skin to muscles what else does your hypodermis do well it helps insulate okay the body why because it's made up mostly of fat is fat a good or poor insulator okay it is a very okay good insulator it's a poor conductor of heat okay prevents heat from losing being lost from the body now men and women are different okay and because of that difference right where we gain fat is also different so in females right you start start losing gaining weight right by accumulating subcutaneous fat in the thighs and in the buttocks okay also the breasts okay in men okay we start to accumulate weight wear well we think of a beer belly right starts accumulated in that region of our body okay so this next part okay of this lecture we're going to talk about skin color okay so here's a global map guys showing you a range of of human skin tone depending on okay different parts of the world all right and what you're what you're noticing here okay we'll get to this more later is that those okay countries that are closest to the equator have okay what well they typically have darker individuals why because okay those countries closest to the equator receive more sun exposure the entire year right as opposed towards the poles all right you see individuals that are lighter skinned okay and why is that well because we're now dealing with individual we're countries i'm sorry okay that receive less amount of sunlight right during the entire year so again it's a trade-off why okay well uv light is good in that it helps stimulate the production of vitamin d from your skin which helps uptake calcium from your diet so there's a beneficial part of uv light at the same time okay there's a there's a harmful effect and the fact that it has short wavelength it's ionizing it can cause now skin cancer so your genetics okay depends on where did your ancestors originate from did they come from a country in the words sunlight all the time or did they come from a country okay with not so much sunlight that's going to dictate then whether or not the lysosomes in your keratinocytes can intracellularly digest or not digest the melanin the umbrellas okay that are protecting the nuclei of your keratinocytes okay so before we get into that okay let's just talk okay about different types of pigments that attribute to your skin tone well there are three different pigments that contribute to your skin color one is melanin the brown black pigment produced by melanocytes and stratum basil we talked about that a little bit right second one is carotene okay it's a yellowish orange okay type of pigment that you find right in fruits and vegetables and you also have hemoglobin hemoglobin's a protein okay that you find within your red blood cells so let's start off with melanin okay so melanin is made up of amino acid called tyrosine right and your melanocytes okay contain an enzyme called tyrosinase so if we go back to our pseudo white board here right we talked about this idea well here is a melanocyte okay that makes melanin and then transfers the melanin to neighboring keratinocytes so that what so that down the melon clusters on the superficial side of the keratinocyte protecting it from incoming uv light okay now the reaction to produce melanin okay occurs within the melanocyte all right so occurring within the melanocyte okay within here the following reactions occurring okay you're taking the amino acid tyrosine okay there's twenty amino acid this is one amino acids okay and through the action of an enzyme inside the melanocyte called tyrosinase okay you produce melanin okay and melanin again is what we're classifying here as these red dots okay brownish blackish pigment clustering on the superficial side of the neighboring keratinocytes okay so that enzyme is present in the melanocyte that helps then convert tyros tyrosine okay into the pigment okay and there's different types of melanin you have ones that are yellow okay reddish brown and also black all right so in some parts of your body you may have concentrated okay amounts of melanin and we think about freckles right we also think about moles those who grow up in the 80s and 90s know who cindy crawford is now a freckle is what it's melanin that is restricted to the basal layer of the epidermis right and these are genetic right these form from exposure to the sun so we'll talk about mendel okay and and dominant alleles and recessive of those later but freckles is what we call a dominant phenotype right so if you have freckles okay you have the genes okay that then give you freckles now one thing you notice about freckles is that what right during the summer times you have a lot more freckles pop up and during the winter times your freckles kind of disappear well why is that well because okay freckles are stimulated by the exposure to uv light okay now moles on the other hand okay they're not stimulated by exposure they're there in the winter and they're there in the summer okay and they don't they don't get darker or lighter and what are moles well moles are clusters of melanocytes that transform into melanin-containing cells so instead of okay making melanin and then transferring to neighboring keratinocytes they kind of just hoard all of the melanin okay and they don't transfer it okay and they and it accumulates in the basal layer of the epithelium of the epidermis it also accumulates in the more superficial layers of the dermis okay now the second type of pigment that contributes to your skin tone is a reddish not reddish but an orange yellowish pigment called carotene okay and you're gonna find them in okay carrots and tomatoes for example okay it's kind of a side note okay is a tomato a vegetable or a fruit well it is a fruit right it's the ripened ovary of a plant it has the seeds inside of it okay is a carrot a vegetable or a fruit well it's a vegetable okay anytime you eat the roots the leaves okay or the stems of a plant right you're eating a vegetable so what is a carrot well eating the root of a carrot all right so both carrots and fruits have carotene so they accumulate where it accumulates in the stratum corneum of your epidermis it also accumulates in the fat of the hypodermis okay so if you ate too many carrots or too many carrots okay tomatoes or carrots okay could you start turning reddish i mean that red but orange is yellowish yeah you will okay and the last pigment that contributes to skin tone skin color is a protein within your red blood cells called hemoglobin okay so typically when you think of hemoglobin you think about a protein that helps bind to oxygen the reason why red blood cells are so good at transporting oxygen is because it has so much hemoglobin in its cytoplasm okay in each hemoglobin actually combined to four oxygen molecules and when hemoglobin is oxygenated okay it actually turns a red color a very bright red color okay we call it crimson red okay so if you're a fan of of alabama right and they say roll tide well it's it's dealing with that reddish color right here right here okay it's that crimson red okay is okay also contributing to your skin tone why is that so if i were to ask okay i always do this when we're actually on campus right if i were to ask someone to walk up and then introduce themselves in front of the entire class okay and let's say that person was a lighter skin person do you think the blood that's in the dermis right could start to shine up okay and project okay through the epidermis the answer is yes we call that blushing right so you come up to the front of the class you're nervous your sympathetic division turns on okay blood starts rushing to different parts your body okay you might turn a little red there okay so even your blood contributes to your overall skin color your skin tone all right so we talked about the idea okay that uv light is beneficial it's harmful beneficial that it helps produce vitamin d in your skin stimulates production of vitamin d okay and harmful in that it's a very short wavelength very ionizing that can mutate your dna right so the trade-off is okay i want to make okay vitamin d i do not want to get skin cancer so if you're living here near the equator right are you worrying about making vitamin d no you're worried about skin cancer so your genetics tells your your lysosomes do not degrade the umbrellas do not degrade right the melanin we got to protect our keratinocytes right from this barrage of uv light because from day in day out okay 365 days a year we're just getting sun right so what happens that the the umbrellas persist in higher levels of strata you're gonna have a darker skin tone okay as opposed to what okay if you're living over here okay are you worried about skin cancer no you're worried about getting enough sun to produce vitamin d so your genetics is telling you okay do not degrade them okay actually degrade the melon i'm sorry okay the sunlight we're getting which we got to get that in here so that means what you don't have melanin and higher strata of your epidermis well then you're gonna have then less pigment okay you're gonna have a lighter complexion okay so we'll stop here guys okay this will be part one of the integumentary system right and then we'll continue on with part two of this packet which will be the last part of this okay particular lecture all right so have a good day i'll see you guys on the next one bye