we're going to discuss the dermis in the hypodermis so we've already talked about the epidermis now we're going to focus on the dermis and the hypodermis the dermis is where we're going to find most of our seseri structures glands hair papilla in other sensory receptors and the hypodermis even though it's not a true part of the skin we will discuss its properties and how it contributes to integumentary system function so this is just an overview of skin in the micrograph and we can see that at the top we have our epidermis okay and then right beneath the epidermis we have our dermis now your dermis is going to contain all four types of tissues but now what are the four types of tissues epithelia connective nervous and muscular so the dermis contains all four types however what we're going to really see is we're going to really see the connective tissue be very apparent now the dermis is composed of two major regions the top 20% of the dermis is going to be the papillary region so it's not very big it's just about this area right here okay and then the rest of the dermis is going to be the reticular region now the popular region is actually going to be composed of areolar connective tissue while the reticular region is going to be primarily composed of dense irregular now the den see regular if you remember is made up of lots of collagen fibers going in all different directions which is great because this gives skin its true strength no matter what way your skin is pulled or tension is created those collagen fibers go in all different directions can add strength to it now we can also see in this picture that we have a hair follicle with hair in it and then there's going to be glands right next to it so we're going to focus on the dermis and the accessory structures now in the papillary region of the dermis it actually gets its name because that's where we find structures called dermal papilla dermal papilla are nipple like projections so whenever you hear that word papilla that word means nipple like projections these papilla happened to be in the dermis so we call them dermal papilla we can see right here that the dermal papilla are basically just these projections that occur they're occurring in the papillary region where the dermis meets the epidermis now dermal papilla basically creates the epidermal ridges and epidermal ridges are what give us the fingerprints now when we talk about dermal papilla they are very very prominent in thick skin if you think about where you have fingerprints epidermal ridges it's going to be on the palms fingertips and soles of your feet the reason that dermal papilla are so prominent in this thick skin is these are the areas that we actually used to grasp so they create more folk surface area and allow us to grip things better thin skin will still have dermal papilla but instead of it being like I call the roller coaster like we see right here so this is more like the roller sir in thin-skinned it's just gonna be wavy like this so they're still present they're just not very prominent now also in the dermal papilla what we will find is a sensory structure called a Meissner corpuscles now to me Meissner corpuscles kind of look like a mitochondria are some people say it looks like a ball of yarn kind of like that now Meissner corpuscles they're also known as corpuscles of touch are gonna be located in the dermal papilla they can be found in both thick and thin skin but you can tell right here that this is thick skin because we have this pronounced dermal papilla here and thin skin remember dermal papilla is gonna be wavy meissner's corpuscle corpuscles are used to detect light touch or what we know as vibrational touch now if you remember we already learned about a sensory receptor that starts with the letter M but we find it in the acai layer of the epidermis those are called Merkel cells Merkel cells in the epidermis well as Meissner corpuscles are going to be found in the dermal papilla so the papillary region of the dermis Meissner corpuscles they do detect light touch very similar to Merkel's but we also often will say it's a light pressure or vibrational touch so we have some differentiation between the two functions the next accessory structure that we're going to talk about are going to be the hair now these sensory structures in the skin the hair nails glands all of them are what we call epidermal derivatives and basically what that tells us is that these accessory structures are derived from the epidermis so all of the sensory structures are actually made out of epithelial tissue so hair has two major parts it has the shaft and that's what you physically see above the skin and then we have the whoot which is what we see below the skin now the root is going to sit in a follicle and the follicle is going to have both an epidermal layer and a connective tissue layer but we're not that concerned with that information so remember we have the shaft that we see above the skin and then we have the root that we see below the skin okay at the bottom of the root you will have a swelling and we call this the hair bulb and in the hair bulb you're gonna have a little nipple light projection called the hair papilla so we're gonna take a closer look at hair so when I go to this picture this is showing us the bulb right here so it's just basically a swelling and in the bulb what we can see is the papilla of the hair which is the hair root patella okay now what's important about the hair root papilla is we have to remember that hair nado to epithelial tissue an epithelial tissue is a vascular but our hair does grow so that means it needs nutrients so we can see that in the hair root cappella we have blood vessels and these blood vessels are going super super close to the hair matrix and what's important about the hair matrix is this is the actively growing epithelial cells so this is the only place that your hair actually grows as the hair matrix moves up here apoptosis will occur and the hair cells will die so this hair root papilla is really important to bring nutrients to the matrix so we can have actively growing hair now attached to the hair are going to be glands on all the glands that are associated with the UM with your integumentary system are going to be considered exocrine glands exocrine if you remember means that they are secreting material to a surface so all the glands that we talked about in the integumentary system are exocrine glands okay these exocrine grains are going to be made out of stratified cuboidal so even if it doesn't look like it it still made out of stratified cuboidal they secrete their material to a surface so the first exocrine gland that we're gonna talk about are the ones that are attached to the hair follicles and these are going to be your sebaceous glands and sebaceous glands are going to be the glands that secrete sebum which is a very kind of thick oily secretion that helps moisturize hair and skin now sebaceous glands are going to be near the hair follicle even if you can't see the attachment they will be near it and every hair follicle usually has multiple sebaceous glands now many people have heard of blackheads whiteheads pimples and basically what happens is the sebaceous gland may become proliferative and sometimes they get plugged and you're in there getting small infections and a lot of times those sebaceous glands will form cysts and the cells are still actively dividing but the ones in the middle die because they're not getting any chance so basically this nasty [ __ ] material so we're about to watch a video on sebaceous glands and a sebaceous cyst if you have a weak stomach do not watch this video it's about a three-minute video of a doctor removing a infected cyst now also since the base just glands are highly proliferative that means that their secretion is going to be holocrine secretion where the entire cell is secreted so to replace the lost cells sebaceous glands have to be able to undergo mitosis rapidly so holocrons secretion is not sebaceous glands do secrete so we're about to go watch this video so again if you have a weak stomach just skip this section of the of the lecture so I hope you enjoyed that lovely video and we're gonna continue on and talk about other glands remember all the glands in the integumentary system are exocrine glands meaning they secrete to the surface and they're all gonna be made out of stratified cuboidal so our next three type of glands are Souter refers glands these are fancy word for sweat glands and we have two main types eccrine and apocrine apron siderophores glands are gonna be your typical sweat glands that we use with thermoregulation we find eccrine glands from your scalp all the way to your toes they're active from birth and again they're used for thermoregulation we also have a perk ring glands ape occurring glands are going to be sweat glands that are only going to be present areas that be that start developing around puberty now they're present at birth but they're not acted till around puberty so we're talking about areas such as your armpits that axillary region face facial region your groin or your in green all region pubic area basically and your chest so the mammary region a Prakrit lands there is a little bit of debate on their exact job but their secretions actually much thicker so they say that it's more for moisturization pleasure and it releases pheromones when it releases its secretion now people that actually don't have your sweat glands eccrine glands usually have ectodermal dysplasia and basically this means that the epithelial tissue that forms your glands never forms and you end up having haifa hydrosis which means that you don't sweat and that's super dangerous because you can't thermoregulate very easily now take a little closer look at glands we can see that we have our sebaceous glands attached to hair follicles and then we have our eccrine glands just go directly to the pores now oftentimes what we will see is apron glands will also be attached to hair follicles but they actually look a little different ok eccrine glands are going to be smaller stratified cuboidal areas so these coiled little circles over here are going to be tighter and apron glands are going to have much larger areas where the secretions are going to be released again remember that apron are going to be found in special areas that become active during puberty and that eccrine are found all over the body so you can have eccrine and apocrine together when we talk about armpits chest groin and facial region now eccrine glands they are going to be the type of secretion that occurs through exocytosis so if you remember exocytosis secretion is known as Mara cream and the name apron tach tells you basically what the type of secretion occurring is apron secretion and this is when pieces of the cell actually pinch off and are secreted so apron secretions are actually thicker not as thick as holocrons but not as thick as the sebaceous glands but apron secretions are still going to be relatively thick merocrine secretion again are going to be more watery so that's your typical sweat glands now the last portion that we're going to talk about are pacinian corpuscle x' pacinian corpuscles they're actually found in the hypodermis but they can't sneak into the dermis so never be surprised if you actually see one deep in the dermis because they can't be present there but most often we find them in our hypodermis also known as the subcutaneous or sub-q layer pacinian corpuscle have a Sukkot named also known as lamb elated corpuscles and to me they actually just look like an onion that's been sliced in half what this is it is actually an axon that wraps around a sensory receptor and they are very deep down into the dermis hypodermis so what they help us detect is going to be deep touch are a lot of times we just say grasping touch or pressure very deep pressure so if someone's slightly like tapping on your skin pacinian corpuscle czar not going to detect that what pacinian corpuscle is will detect is if someone actually pushes down really hard art they grab you so to do a quick review and we're just going to use this picture I have here we have three major different sensory receptors we went over we have Merkel cells that we found in the epidermis you have meissner's corpuscles that we find in the dermal papilla they detect light touch but we law often say like pressure or vibrational touch to have a difference between Merkel cells and then we have pacinian corpuscles which are going to be deep pressure now one I did not go over would be free nerve endings so you have a lot of different sensations besides pressure and touch you have pain temperature tickling and these are all going to be detected by free nerve endings and if you look really really closely in this picture what you're seeing are these just these little yellow lines those are all free nerve endings and they're gonna have different names depending on what they detect so thermo receptors are gonna detect temperature nociceptors are going to detect pain so anything that's not touch and pressure is going to be usually be detected by free nerve endings