what is the largest organ out of all of our body systems it's our skin and that's exactly what we're going to be talking about today with the at's version 7 human anatomy and physiology portion of the exam focusing on the integumentary system let's get started let's talk about the skin being the largest organ it's quite appropriate that it belongs to a system with such an extensive name the integumentary system but you might be asking yourself why is this skin so important when you think about it there's actually several reasons why it plays a crucial role in maintaining homeostasis by regulating our internal body temperature as well as fluid balance the skin can also act as a physical barrier protecting internal structures and organs from damage it guards against invasion of pathogens like bacteria and viruses and it's the site where vitamin D synthesis occurs skin also possesses sensory functions so for example if a worm was to touch your foot you would typically be aware of its presence and if you're like me you would be going running and screaming in the other direction the integumentary system is layered featuring various tissues as well as different cell types let's begin by breaking each one of these layers down let's start by discussing a type of cell found throughout the epidermis known as keratinocytes keratinocytes produce keratin which is a protein that enhances the water resistance and toughness of our cells these types of cells originate down here in the bottom of our epidermis and they slowly push their way up towards the top known as our superficial layer where they undergo a process known as cornification cornified cells hence the name of our most superficial layer stratum corneum means that these cells are hardened flooded and they are tough at this stage within our epidermis they are dead which means that they've lost their organel and they're filled up with that keratin instead before we delve deeper into the layers of the epidermis it would be useful to have a pneumonic to help us remember the sequence at which these layers occur from the outermost to the innermost here's a neonic that I like to use it's called come let's get sunburned the first letter of each word stands for each letter of our epidermal layers starting at the top of our epidermis we have the stratum corneum and this layer is composed of those cornified cells those dead cells that are continuously being slothed off so that new cells can arise from the layers below to replace them just below that later is the stratum lucidium and this is where you're going to find that more thick skinned areas you're going to find a lot with the soles of your feet as well as the palm of your hands this layer also consists of cornified cells which is a protein that gives them this transparent layer appearance hence the name lucidium next up we have the stratum granulosum and here those keratinocytes push up from those lower layers and they begin to flatten out and begin to accumulate granules as suggested by the layer's name these granules perform various functions including forming a water protective layer for the skin those keratinocytes in this layer will eventually lose their organel and then they're going to transform into those more cornified cells in the upper layers moving deeper we have the stratum spinosum which contains several layers of those KERO sites but it also houses a particular type of cell called the langerhan cell these langerhan cells that are found in this layer work similar to that of a microf fodge consuming up worn out cells and bacteria what's interesting is that the name of this layer comes from its appearance when you look at it under a microscope it looks kind of spiny when it's stained the deepest layer of the epidermis is called the stratum Basile it consists of a single layer of Basil cells which are constantly undergoing mitosis to produce new keratinocytes which are then going to migrate upwards to the more higher levels if you have thick skin on maybe your feet or even maybe a callus on your palm it's likely due to this stratum Basile layer it responds to those frequent abrasions by producing more cells thereby thickening that stratum corium above it Additionally the stratum basil is going to contain melanocytes which produce melanin that's a pigment that contributes to the skin color and provides protection against UV radiation the melanin is transferred to keratinoid in structures called melanosomes another type of cell that can be found here are Merkel cells whose precise function is still under study but it's believed that they're involved in the nervous system particularly enhancing our sense of touch the stratum Basile is the deepest layer of our epidermis and it's tightly connected to the dermis which we're going to explore next unlike the epidermis the dermis contains blood vessels it is also composed of connective tissue a type of tissue distinct from that epidermal layer that serves to bind structures together within our body you can think of the dermis as kind of like the glue that connects everything together within the dermis you can also find things like sweat glands nerves as well as hair follicles which are all integral to the Skin's function this layer is also reinforced with fibers and there's two key types of proteins we have collagen and we have elastin collagen provides more of a structural support and alasin grants us our elasticity these particular proteins are produced by specialized cells known as fibroblasts which are located throughout the dermis the dermis is divided into two primary layers we have the papillary layer which consists of looser connective tissue and we have the reticular layer beneath it which is the connective tissue that's more densely packed together before we move on to the hypodermis it's pertinent that we take a moment to discuss scars when we have more superficial cuts it will only affect the epidermis generally not leaving a scar behind however deeper cuts that do reach that dermis often result in scarring these scars are typically going to appear distinct from the surrounding tissue because their formation process is going to differ from the original skin structure this difference arises because during healing fibroblasts produce collagen but they do not align the same p pattern that they were originally present additionally features like sweat glands and hair follicles which we're going to discuss a little bit later are not regenerated in that scar tissue consequently scar tissues usually have reduced elasticity which means extensive scars with those much more larger wounds can eventually impact mobility in some cases we may see keloids which are irregular fibrous tissues formed at the side of a scar due to increase collagen production now we're going to proceed to our final layer which is the hypodermis also known as the subcutaneous tissue layer positioned beneath the dermis that hypodermis is a connective layer that links the skin to the underlying bone and muscle tissue what's important to know is that the hypodermis is primarily composed of adapost tissue which is essentially stored body fat this layer plays a crucial role when it comes to providing the body with insulation now that we've explored the layers of the skin let's discuss some accessory structures that we haven't yet covered such as our sweat glands sweat glands play a critical role when it comes to cooling the body through persperation which is just a fancy way of saying sweating however sweat glands are not the only method that the skin uses to regulate temperature blood vessels in our dermis can actually dilate or widen allowing heat to escape through the skin conversely in cold temperatures where we need to maintain our Heat our blood vessels can actually constrict and draw that heat away from the surface so that we can conserve it inside the body another key accessory structure is our sebaceous glands these glands produce oil that's going to help waterproof and lubricate our skin as well as our hair this oil production is vital in maintaining the health of our skin and the moisture of The Kino sites we discussed earlier hair follicles if you recall are found within the dermis layer of our Skin Within These hair folli more specifically at the base of our hair bulb cells are going to rapidly undergo mitosis as these cells continuously multiply they are going to push outward driving the growth of the hair root the visible part of our hair known as our hair shaft is composed of keratin and is non-living so when we talk about Nails Nails originate from our epidermis specifically from the base known as a nail root just like we saw with hair follicles this area is going to contain cells that are actively undergoing mitosis as these cells continuously multiply they are again going to push outward which contributes to the growth of our nails the visible part of our nail known as the nail body serves to protect the tips of our fingers and toes and is composed of those dead keratinocytes as with all of our videos I always like to emphasize the importance of understanding the why why is it essential that we learn about the integumentary system a key reason for this is the prevalence of skin cancer skin cancer is the most common cancer in the United States current estimates that it's about one in five Americans will develop skin cancer in their lifetime and it's also estimated that approximately 9500 people in the United States are going to be diagnosed with skin cancer every single day skin cancer can develop when the cells of the integumentary system begin to malfunction and divide uncontrollably so for example the basil cells in our epidermis can develop into basil cell carcinoma it's the most common frequent type of skin cancer found in humans similarly melanocytes the cells responsible for producing our melanin can also become cancerous and lead to melanoma a more aggressive type of skin cancer Squam cell carcinoma is a common type of skin cancer that arises from the squamous cells which are those flat thin cells that make up the outermost layer of our epidermis this form of cancer is primarily caused by the prolonged exposure of ultraviolet radiation either from sunlight or even from tanning beds leading to the DNA damage of our skin cells and lastly we're going to discuss Burns and in this particular situation the Skin's function is going to be severely compromised burns are typically categorized into degrees based on the depth of the skin that it has damaged Burns can be classified into four four main classifications we have first degree burns which affects our epidermis we have second degree burns which extends into the epidermis and the upper layers of our dermis we have third degree burns which is going to penetrate down into the depths of our epidermis and our dermis and then lastly we have fourth orre Burns which is going to go all the way down to damage those deeper tissues potentially even affecting muscles and Bones interestingly enough when we have third and for degree burns they can actually cause less pain than those milder Burns that we see more superficially due to nerve damage taking place significant Burns pose serious risks when it comes to impairing the Skin's essential functions such as things like fluid retention or even protection against those external threats and lastly the damaged skin is highly susceptible when it comes to infection so we have to make sure that we address this promptly to prevent any other complications from taking place I I hope that this video is helpful in understanding everything you need to know for the atits when it comes to the integumentary system as always if you have any questions make sure that you leave them down below I love answering your questions head over to nurse store.com where there is a ton of additional resources in order to help you Ace those ait's exams and as always I'm going to catch you in the next video bye