right as we go through this unit we're going to be looking at uh first uh section being the integument so the integumentary system is the skin first and foremost But it includes more than just the skin it's any of the accessory structures like hair and nails glands sweat glands oil glands um but also the blood vessels muscles and nerves that serve the different parts of the skin um the purpose of the integument is to First maintain body's Integrity it is a protective mechanism so it keeps things outside the body that should stay out and things inside that should stay in but more than that the body is important in maintaining or the skin is important in maintaining body temperature um it does this for example when you're cold the hairs on your skin stand up uh and that's to affect blood flow around the skin and save heat uh also um when you're hot you're going to sweat and that gives off heat as that sweat evaporates it takes heat with it um in the sunlight the skin is important to converting or activating vitamin D um it doesn't synthesize it it just activates it um it's also important for sensory information and by all of these functions maintaining homeostasis so when you're looking at the skin it has three main layers the outside being the epidermis which is very thin here then you have the dermis which is a rather large layer and then underneath the dermis you have subcutaneous fat the subcutaneous layer which is also referred to as the hypodermis now the epidermis is going to be epithelial cells the dermis however is connective tissue so when we're talking about skin there's actually two types you have thin skin and thick skin thin skin is all the part of your body that you have hair which is basically everywhere on your body except the palms of your hands and the soles of your feet everywhere else uh you should have hair uh thick or hairless skin is found in those locations The Palms and the soles of your feet now in the epidermis there are four types of cells you have keratin aites and they produce keratin this is a fibrous protein that um conveys protection so the bulk of the cells in your epidermis are keratin aites you also have melanocytes and they produce melanin which is a pigment you have intradermal macrofagos macrophages are cells of the immune system so these are macrofagos uh that are part of the immune system they phagocytose bacteria um among other things and then you have tactile cells and these are sensory cells so um there are four layers to the epidermis unless you're in thick skin if you're in thick skin there are five layers the deepest layer is the stratum basal these are where your cells are replicating then as they go through this process and move upward you can see how they change shape and size as they move upward they fill with keratin and they die these cells down here are highly mitotic they are reproducing very rapidly in this stratum Bay cell then you can see as they go up to the next layer called the stratum spinosum they begin to flatten out so these cells down here are almost cuboidal but by the time they get here you can see they're starting to flatten uh stratum granulosum even more so and then the stratum corneum these are flat dead keratin fill cells the stratum lucidum here in the layer between is the extra layer that you have in thick skin so basal spinosum granulosum lucidum if it's pregnant or present and then the corneum now pigments are produced by melanocytes melanos sites are found in the stratum Basile layer now the skin color that you get has to do with how much melanin is produced um and then how much of that melanin is then taken up by keratin aites uh to determine the darkness of the skin and there are actually many genes that control this like several four five6 um I don't know the exact number I don't know that anybody knows the exact number um but it is genetically determined and there and as you can see if you look at any room full of people there are many different uh variations in skin color now moving under the epidermis you have the dermis the dermis actually is two layers the uppermost is the papillary layer which you can see here this papillary layer is part of what firms fingerprints okay and then you can see the stratum basal here uh in a basement membrane connecting your epidermis to your connective tissue then this one is your um reticular layer the reticular layer is very irregular connective tissue uh beneath the epidermis and the dermis you have your uh subq layer or the hypodermis and this attaches the epithelial tissues to underlying tissues now also notice there's lots of structures in the skin you have different types of glands you have blood vessels you have hair follicles and you can see this papillary layer and how it meets up with the dermis there