Health and medicine
- Meet the skin! (Overview)
- What is skin? (Epidermis)
- What lies beneath the epidermis? (Dermis and Hypodermis)
- Where do our nails and hair come from?
- What's in sweat? (Holocrine, Apocrine, Merocrine Glands)
- LeBron Asks: Why does sweating cool you down?
- Overview of Sensation and Meissner's Corpuscle
- Pacinian's Corpuscle and Merkel's Disk
- Ruffini's Ending and Hair Follicle Receptor
- Pain and temperature
- Thermoregulation mechanisms
What lies beneath the epidermis? (Dermis and Hypodermis)
Created by Raja Narayan.
Want to join the conversation?
- So if a 1st degree burn just singes the epidermis, how can you feel it? I was under the impression that the epidermis has no pain receptors.(14 votes)
- The receptors from below can... .Otherwise, when someone lightly touches you, they're only touching the epidermis but the receptors in the dermis can sense it... These same receptors respond to the pain by shifting and then NA+ and other ions get in and start the Action Potential on the nerve fiber that the receptors are connected to. This AP eventually reaches the brain! ( for more clarification on how the receptors work I would like at the continuing videos ) ..... Hope you understood(16 votes)
- How big are these layers individually (mm)?(5 votes)
- The epidermis is 0.1 mm on average in thin skin and up to 1 mm in thick skin.
The dermis is 0.3 mm on the eyelid and up to 3 mm on certain areas of the body.
The hypodermis is about 4-5 mm on average (can vary quite a bit across certain areas of the skin).
Hope this helped! I'll be researching this more!(11 votes)
- Different online sites say that the arrector pili muscle is in the reticular or papillary dermis. In these videos the speaker alternates between the reticular and the papillary dermis. Where is it actually located and why is there so much confusion! Help! Thanks!!!!!!!!!!!!!!!!!!!!(3 votes)
- Arrector pili muscles span both layers of the dermis, they originate in the papillary dermis and attach to hair follicles in the reticular dermis.(5 votes)
- what makes hypodermis necessarily not skin?(5 votes)
- If your nerve ending is killed is it good or bad?(2 votes)
- If nerve endings are killed that tends to be very bad since that means the nerve cannot feel anything.(4 votes)
- So if you sustain a First- Degree Burn, you feel the most pain straight away as opposed to Second-Third Degree burns due to the nerve endings being burnt off? Does the nerve endings being burnt off result in long term potential damage?(1 vote)
- Third degree burns hurt the least, because nerve endings have been destroyed. First and second degree burns hurt more because less tissue has been damaged.(3 votes)
- once I got a burn which was black and very painful.it was so painful that I screamed for hours. Was it a first, second or third-degree burn?(2 votes)
- I have heard of 3 degrees of burns, 6 degrees of burns, and 4 degrees of burns. I think the 4 degrees is pretty standard.
1st degree: epidermis
2nd degree: dermis
3rd degree: subcutaneous fat or hypodermis
4th degree: muscle and bone
How would you even be able to survive a 4th degree burn which burns major blood vessels like the femoral artery for instance?
I mean stem cells will come to the site and form muscle cells, fat cells, cells of the dermis, and cells of the epidermis as well as most of these going through mitosis but you get major arterial bleeding in a 4th degree burn and it might be very painful to the pressure you put on those blood vessels.(1 vote)
- Those kind of burns are extreme emergencies if you do happen to survive (and if you did, you would likely wish you hadn't).(2 votes)
- The current 10th edition of both the Marieb Human Anatomy and Physiology and Martini Fundamentals of Anatomy and Physiology texts refer to second degree burns as one of the partial burns involving the epidermis and upper dermis. This burn blisters, is painful and red, They both describe third degree burns as full-thickness burns involving all of the layers of skin, and which appear "gray-white, cherry red, or blackened." Since nerve endings have been destroyed, the burned area is not painful. Are these Pearson texts incorrect in their classification of 1st, 2nd, and 3rd degree burns?(1 vote)
- This topic all depends on the book you are reading. For example Medical-Surgical Nursing 9th edition by Lewis,Dirksen, Heitkemper,Bucher has the degrees as first degree equals superficial partial thickness, second degree as deep partial-thickness, third and fourth degree as full-thickness burns. In this book they also like your book rate the second degree level (deep partial-thickness burn) as the most painful.
But to contrast that, I have another book I use for nursing (I use the above mentioned book too for nursing). The other book is High Acuity Nursing 6th Edition by Wagner, Hardin-Pierce. Their burns are by depth so not by degrees. Their categories are superficial, superficial partial-thickness, deep partial-thickness, full-thickness, and subdermal burn. Their most painful level is superficial partial-thickness burns. And I have learned that Wager textbook is more right than the Lewis textbook. The most painful level is supposed to be superficial partial-thickness burn because the nerve endings are not involved. The deep partial-thickness burn has the nerve endings involved meaning they were burnt.
Now it sounds like your second degree is the superficial partial-thickness burn since it involves the epidermis and the upper dermis. Sounds like every book is different. I also saw that the High Acuity Nursing by Wager does have a degree picture and they are saying first degree is the epidermis, second degree is dermis, third degree is subcutaneous tissue, and fourth degree is muscle and bone. So looks like here they are saying superficial partial-thickness and deep partial-thickness is the same degree of burn though the very next page says that the characteristics are different (one is painful, one is not, etc).(1 vote)
- Where is the basale lamina is it above the dermal papillae and below the stratum basale or am I getting this confused ?(1 vote)
- [Voiceover] So, now that we've talked about the epidermis, or our top most layer of skin, let's descend further down, and talk about the dermis, these next two layers of skin, and then we'll also talk about the hypodermis, which is the bottom most layer of skin here. So as you can see, your dermis has two layers to it, and again, it sits right below your epidermis, so your epidermis, the top most layer of skin sits up here, and if you can recall, the bottom most layer of your epidermis is called the "stratum basale," the basal layer of your epidermis. So below that we have our first layer of the dermis which is called the "papillary dermis." This is the topmost layer of the dermis, and then below the papillary dermis, we have what's called the "reticular dermis," the reticular dermis, right here. The main difference between the dermis versus the epidermis is the type of tissue we have here. Recall that in the epidermis, we had "epithelial tissue." So, I'll write epithelial tissue, up here. And then within the dermis both layers are going to have something that's called "connective tissue." You've probably seen that written out as CT (connective tissue). So connective tissue is different in that it doesn't necessarily involve cells. Epithelial tissue involves things like simple squamous epithelial cells, columnar epithelial cells. Even transitional epithelial cells, that you may have seen in the bladder. And your connective tissue contains a litany of other proteins. Things like actin which is what you must have heard of when we talked about the muscular system, or collagen which is another structural protein. These are some of the most popular proteins you see mentioned when we talk about connective tissue, but they also include things like laminin, elastin, desmin. Connective tissue mainly holds things together. If you remember a tendon, a tendon is connective tissue that holds the muscle onto a bone, and between the papillary dermis, and the reticular dermis, there are two types of connective tissue we see here. In the papillary dermis we have very thin, loose connective tissue, and this allows for all the stuff in the papillary dermis to sort of move around and change shape and position, versus what we have in the reticular dermis which is thicker, more dense, or denser connective tissue. Denser connective tissue, and the purpose of this is to make things stay still. We anchor things down in the reticular dermis, and we'll talk exactly about what we're anchoring down here in a moment, but as we hop back up to the papillary dermis, there are a variety of things that we have here that have to change shape and position and are able to do so because the connective tissue is so loose. One of the main things we find in the papillary dermis are blood vessels. If you recall when you have an arterial from an artery branch off into a capillary, so you've got these purple capillaries right here, and then come back together to make a venule, a venule which goes off to a vein. Realize now that this is the most superficial or the topmost layer of your skin that actually has blood vessels here. So one of the roles is that the capillaries have to deliver oxygen and nutrients that nourish not only your dermis, but actually go up into the epidermis as well because the epidermis doesn't have any blood vessels. It relies entirely on the papillary dermis to nourish it, and thank goodness this is thin, loose connective tissue because there's plenty of room here for the capillaries to engorge with blood, fill up with nutrients, and then these nutrients can diffuse across and go up from the dermis into the epidermis, and even go lower, if necessary. The other thing we have in our dermis are nerve endings. These nerve endings, and I'll write this just because my drawing is not as obvious. These nerve endings that sit in our dermis allow us to perceive things like touch and even pain, and then that will pass on a signal across the nerve going in this direction right here, like that, and this signal is relayed all the way to a cell body, and this cell body can sit somewhere much further away than the skin. Now as we get to the reticular dermis we'll see why it's important to have thick, dense connective tissue down here, and this connective tissue helps anchor things down. One of the things that you can have, and I'll sort of draw it like this ascending to your epidermis and so it leaks out over here. This is a gland. You'll have tons of sweat glands and exocrine glands of other varieties that start in your reticular dermis, and are anchored and held down here that extend out with a duct to secrete their contents to the epidermis to the outside world, kind of at the top layer of your skin. So you've got plenty of glands that sit here. In addition, you'll also have this follicle right here. This follicle will have from it emerging a hair. This hair ... I guess I should label this also. The hair, of course, is going to protrude at the top of your skin. It's not that you just have a hair that sits inside and then this guy right here is just your hair follicle, and so your hair follicle is anchored within your reticular dermis, and the hair itself is allowed to grow and extend out to the top and protrude from your epidermis. One of the other things that we have kind of sitting in your dermis that's anchoring itself onto the hair, or the hair follicle, is this slab of muscle that we've got right here. So this guy, I'll write if off there, this is an "arrector pili muscle." An arrector pili muscle, and this is involved in extending or having your hair stand straight up when you're cold or when you're scared. Finally, now that we've talked about the dermis, we can move to our last layer of skin. Although, it's technically not skin, but it's called the "hypodermis." This is the hypodermis, which is a great name because as you might recall, hypo just means "below" and this layer sits right below the dermis. Another name for it is subcutaneous fat, and I think that that's also a great name for what we have here. Subcutaneous, if you might remember, cutaneous is just another name for skin, so subcutaneous fat, and that's exactly what we have down here. We have tons of layers of fat that could vary from person to person, and although fat gets a lot of flack we have to realize that it's very important because there are two main functions they help us achieve. First of all fat absorbs shock. People that are more insulated with fat are able to withstand traumatic injuries, maybe more effectively than others, and the other thing that it does for us is that it insulates our tissue, because realize that now that we've finished talking about our skin, we've talked about the epidermis, the dermis and now we've even covered the hypodermis. What sits right below this? You're going to find muscle. Muscle sits down here. It's below that and perhaps even bone. You know, if you're talking about your chest wall right above your rib, if you put your finger right kind of where your clavicle is above your rib cage, or even on your ribs, realize that your epidermis, dermis, and your hypodermis are all that separate your finger from your rib bone, or even your muscle if you're pressing on your bicep or your calf. We spent a lot of time kind of talking about the components of what's in our skin, but how does this even help us clinically? How do doctors use this to diagnose diseases? The best one to talk about as an example here would be for the diagnosis of burns. Now a burn is a horrible thing that could happen and one of the things that we do to differentiate the types of burns you can have is to say what degree of a burn you sustained, and interestingly enough the different layers of your skin correspond to the different degrees of burn you can have. You can have a first-degree burn, which is just sort of a reddening that can occur on your epidermis. You can have a second-degree burn, which is characterized by burning into the dermis, so much so that you don't have nerve pain after some time. That's the difference between a first-degree and a second-degree. A first-degree hurts awfully, but if you have a place that's been burned that doesn't hurt so much anymore, it's because you've burned and killed off nerve tissue here, and so they're not able to send a signal up to the cell body. And then finally there's a third-degree burn, which is going past the hypodermis into things like your fat, the muscle that's below, the bone that's below as well, and, of course, the third-degree burn is characterized by not having any pain, and having more of a darker coloration to it, because now you're burning more than just connective tissue. You're actually burning bone or muscle, or fat, as well. It's this exact anatomy, right here, that we've talked about that allow doctors to distinguish between whether a patient has sustained a first, second, or third-degree burn, and that's something you can do now as well.