so here we have a model of the integument and we can see the layers that is divided in two we can see the epidermis here which is this part that sits on top and we can immediately see that we have a difference in thin skin right here versus thick skin which is over here we can see that not only is thick skin thicker in the outermost layer but we also have this extra layer of cells and thick skin so if we go from superficial to deep we encounter the stratum corneum first that hard horn layer that's full of cross-linked keratin below that and thick skin only we have the single layer of cells called the stratum lucidum which means the clear layer below that we have the stratum granulosum which are in this model these the elliptical cells and then below that we have the stratum spinosum which contains the spiny cells this is where keratin production really begins of them the spiny layer and in really kicks into high gear in the granular layer with the stratum granulosa at the base of all this we have the stratum basale a also news the stratum germinativum because this is where we have our stem cells that are dividing that's this dark blue here and this is sitting on a basement membrane and the basement membrane is the interface between the stratum germinativum and the underlying dermis now here they've taken away the epidermis so that we can see the dermal papilla a little bit better and if we were look down on this model we would see these mounds it has a sort of an egg crate egg carton appearance with these wavy undulating mounds now we can say that the waviness of the basement membrane and the stratum germinativum follow these mounds and that way venus is called the epidermal ridges so when we look at them in some cases the epidermal ridges especially on the palms of the hands the soles of the feet will give rise to fingerprints and dough prints on the surface of the scat so once we have seen the stratified squamous epithelium that comprises our epidermis we can look at the dermis and the dermis here in orange comprises the papillary layer and the papillary layer on this model you can see it as this plexus if you will blood vessels that basically end in capillaries in these dermal papilla and the papillary layer is defined from about here and then they didn't continue the blood vessels long on the side of the model that you can imagine that they would continue on through the skin and this is about the extent or the limit of the capillary layer below these blood vessels we have the reticular layer and you can see this is where we have a lot of our deep structures our accessory structures originating so we can look at several of these including our hair follicles here and hair follicles often have these sebaceous glands associated with them this is one in three-dimensions here's one that's been cut through longitudinally so you can see inside the sebaceous gland and you can also see inside the hair follicle you could see the hair and here we have the hair bulb the hair root and then we have the shaft of the hair that projects through the epidermis we can also see that we have a muscle a smooth muscle associated with this hair follicle this is called an erector pili muscle and that is what causes the hair to stand on end so if somebody gets cold or they get frightened the hair will stand up on end and this and other animals has a lot of value because of your stands upon end it creates an insulating layer that's one reason and another reason that the hair will stand up on end when you're frightened is if you look at animals like cats when they are confronted they usually what do they do they arch their backs and their hair stands on end and this is to make them a little bigger so that a potential predator or a potential confrontation can be avoided with another animal because it might be a little bit scarier to be bigger so that's those are two functions of the erector pili muscles and these are smooth muscles associated with hair follicles now I can see lot of vasculature in here so we also have what is called a cutaneous plexus and this basically is a bunch of blood vessels and here we see the cross-section coming out of the model towards you so we can see these blood vessels that are distributed throughout the right at the border between the dermis and hypodermis some of these blood vessels give rise to what will become the papillary it's some text called the sub capillary plexus that's these vessels here that have their capillaries in the dermal papilla now let's look at some of these other structures within the reticular layer here we have a sweat gland and this is a suit or a sweat gland or a merocrine the sweat gland and this gives rise to the watery sweat that we have with sensible perspiration that is what we have and we're exercising or when we get high so a lot of these glands you'll find them all over the body there's another type of sweat gland not shown here called an epic run sweat gland and those are found in the groin in the armpit area in humans here we can see American sweat gland that hasn't been cut through longitudinally so you can see inside and you can see it's this coiled tubular structure you could see the coiled tubes inside and then of course we have the duct that empties out on to the surface of the skin now we can also see some of these things this is nervous tissue right here so this is what's going to relay the signal from some of our sensory structures in the skin like this right here is a tactile corpuscle also known as the meissner's corpuscle that is found in the dermal papilla and i'm not going to make you memorize that or know that but just be aware that you have a lot of sensory structures within the skin here's another sensory structure that's deep and this is called a laminated corpuscle because it has these lamella or layers and this is very good for sensing deep pressure or vibration and so forth now notice that we have the division of the papillary layer by this papillary plexus the reticular layer and remember that we have within the reticular layer our dense irregular connective tissues and this is also the layer which gives rise to most of our accessory structures the border between the reticular layer and the subcutaneous is not that little defined you can see that there sort of it it's a diffuse border and we see it the vasculature is right along the edge of the border between the reticular layer and the hypodermis also known as the subcutaneous and as we remember the hypodermis is not actually part of the integument but it is that connective tissue layer that is sometimes called the superficial fascia that directly underlie the cutaneous membrane so we remember that our cutaneous membrane is our epidermis and our dermis and our cutaneous membrane is one of two parts of our integrant the other part of the integument are these accessory structures that originate within the dermis so when we look at the hypodermis we see that it has mostly adipose tissue and some areolar connective tissues and this is what's going to allow your skin basically to slide over the underlying structures such as muscles and so if you are if you flex your muscle for example when you flex your muscle the skin has to stretch over it and move be able to move so these things have to move independently and this is one of the primary purposes of the hypodermis but of course we see it has a lot of adipose tissue so it can also insulate because adipose tissue is a very good insulator against cold so because this is either fat cells these are very good for insulation you can have some energy storage in here as well in fact there are some populations that live in very cold climates such as the Inuits and the Aleutians they tend to have a little bit more subcutaneous fat because they need that extra insulation against the cold weather another group of people that have a little bit extra adipose in the subcutaneous are distance open water swimmers so these are people who swim in very cold water and host issue gives them two advantages one its insulating against the cold water but another reason is that the adipose tissue itself is less dense than water so it gives them a little bit more buoyancy as well