Full transcript
0:00So, this video will continue the
0:02overview of the integumentary system.
0:05And once again, I'm just going to give a
0:06little bit more detail on each of the
0:08layers. Once again, going from
0:10superficial to deep, we have the stratum
0:12corneum,
0:14which is the top most keratinized layer,
0:16the stratum lucidum, only in thick skin,
0:19the stratum
0:20stratum granulosum,
0:22stratum spinosum, and then stratum
0:23basale.
0:25This just shows us once again thin skin,
0:27which again same layers we can see in
0:29that deepest stratum basale, we may see
0:32mel- melanin, which would give the skin
0:34its pigment.
0:36All right. And so, the stratum basale,
0:38that will literally means basal layer or
0:40deepest layer,
0:41and it's firmly attached to the dermis
0:43beneath. And the dermis we're going to
0:45talk about in a little more detail. It's
0:47areolar as well as dense irregular
0:49connective tissue, and those tissues are
0:51going to provide the nutrients and
0:53oxygen necessary for all of the cells
0:56overlying them to survive.
0:59The stratum basale is a single row of
1:02mitotically active cells. Sometimes you
1:04might hear different textbooks call it
1:06the stratum germinativum. And so,
1:08germin- germinate means to divide. Um
1:12and so, it's because these cells undergo
1:13cell division.
1:15The cells are going to migrate from this
1:17layer, the stratum basale. We can see a
1:19mitotic figure here,
1:21and they're going to um
1:23eventually differentiate as they move
1:25more superficially. And so, as they
1:27migrate, the journey is about 30 to 45
1:30days for a cell to divide, and then
1:32ultimately be sloughed off.
1:35And so, we can see here would be that
1:36stem cell, undergo cell division, those
1:40two cells now move uh upward or more
1:42superficially, and that continues.
1:46The melanocytes are also found within
1:49that stratum basale, as well as those
1:51Merkel cells as we mentioned.
1:55The stratum spinosum, so again spinosum
1:58I typically think spiny or spiky or
2:00prickly network. And these cells are
2:02going to have melanin granules that they
2:05accumulate from those melanocytes, as
2:07well as the intermediate protein
2:09keratin. So, keratin is the protein that
2:13all epithelial cells will possess to
2:15make them be good epithelial covering.
2:19And once again, in this layer, the
2:20stratum spinosum, we'll find Langerhans
2:23cells or dendritic cells, which are
2:25going to help to um
2:28engulf and present foreign invaders to
2:30our immune system. And so, these
2:32dendritic cells, here's a nice electron
2:34micrograph of one. These are highly
2:36aggressive, um meaning that they're
2:38going to engulf
2:40or phagocytize, and so that literally
2:42means phagy to eat, cyto cell. So,
2:45they're a cell that eats things. And so,
2:47they might engulf a foreign bacterium
2:49and then present it to the immune system
2:52and activate an immune response against
2:53that bacterium.
2:56The stratum granulosum,
2:58so because it has granules within this
3:01layer. So again, this layer is about
3:03three to five cell layers thick.
3:05You can see one of the characteristics
3:07are that these granules, which are
3:09called um
3:11which accumulate keratohyalin and also
3:14um
3:14also considered lamellated granules,
3:17they crosslink keratin as well as
3:19provide waterproofing to slow any water
3:21loss. So again, that helps us to have
3:23that nice waterproof layer um
3:26to protect from our outside environment.
3:29And then these are the last viable cells
3:31or the last living cells. Above that,
3:33all the cells in the stratum corneum are
3:36too far away from the dermis underlying
3:40that they are all dead.
3:43And once again, lucidum is only in
3:46the thick skin, which we find on the um
3:49surface of our hands and our feet. And
3:52so, that word lucid, I feel like it's a
3:53good SAT or GRE word. So lucid means
3:57clear, and so we see that additional
3:59layer for additional protection.
4:02And then finally, the stratum corneum is
4:05that outermost layer. It can be up to 30
4:07cells layers thick, and once again,
4:09those cells are dead. They still possess
4:11glycolipids, so glyco being sugar um
4:15monomers and lipid molecules that extend
4:19off the surface of the plasma membrane
4:21to help waterproof
4:22um
4:23sorry, and also in the in inter
4:25uh extracellular space to help provide
4:28waterproofing for our skin.
4:31And then our dermis, we've alluded to
4:33this, but this is going to be the
4:34connective tissue layer upon which the
4:37epidermis lies. And so lots of fibers
4:40here, collagen, elastin, reticular
4:43fibers, and this is the area that
4:45between those fibers and packed in will
4:48have blood vessels.
4:50And so collagen, as we talked about
4:52earlier, is a um
4:55a a protein that can pack lots of water
4:58densely. And so our dermis is going to
5:01be the sort of a go-to place. If you are
5:03ever dehydrated, the vessels there are
5:06going to reclaim water from the
5:08extracellular environment into our blood
5:10vessels and help to increase our blood
5:12pressure blood volume by going to that
5:15very aqueous or water-filled site.
5:18Within this area, we'll also find lots
5:21of different um structures such as sweat
5:23or sebaceous glands,
5:25nerve receptors. We call these um often
5:28corpuscles. We have hair follicles,
5:31lymphatic vessels, and lots of cells
5:33like um
5:35fibroblasts and connective tissue.
5:39And so the two layers of the dermis, so
5:41this shows us close up the epidermis
5:43sort of peeled away from the dermis, and
5:46we see these little, what they call
5:47papillae,
5:49um, or foot-like projections that extend
5:53upward into the dermis. So, they're sort
5:54of, um,
5:55involutions that the dermal papillae,
5:59um,
6:00make are what makes our fingerprints, by
6:03the way.
6:04And so, the papillary layer is going to
6:06be loose connective tissue, specifically
6:08areolar connective tissue.
6:10We can find those dermal papillae, and
6:12then one of our specialized, um, nerve
6:15receptors are called Meissner's
6:16corpuscles, and those are usually along
6:19those papillae.
6:21So, those will transmit a sense of light
6:22touch, along with our Merkel cells,
6:24which were in the epidermis.
6:26And then deep to that papillary layer is
6:29the majority, or 80% of that dermis, and
6:32that will be dense irregular connective
6:34tissue. So, once again, lots of collagen
6:37gives us strength and resiliency, also
6:40packs water, allows us to have skin, um,
6:43or the integument as a whole, to, um,
6:46rely on for hydration and proper proper
6:49blood pressure and blood volume.
6:53All right, this just shows us once
6:54again, here's that 30-cell layer thick
6:57stratum corneum. We see all the
6:59different layers of the epidermis, from
7:00the corneum down to the basale. Here we
7:03have those papillae extending up into
7:06the epidermis, and then lots and lots of
7:08collagen here, those irregularly shaped
7:11pink bundles of protein that's going to
7:14pack water.
7:16And this just shows us some really neat
7:18electron micrographs of that areolar
7:20connective tissue, much more loose than
7:23our dense irregular connective tissue,
7:25um,
7:26in the reticular layer, that will be
7:28more dense.
7:29Okay, and one thing I just want to
7:31mention is that if you, um, have a pet,
7:34or if you've ever worked, um,
7:36brought your pet to the vet, and they
7:37were dehydrated, one of the things that
7:39the veterinarian will do is to, um, kind
7:42of gather up the fur and pull the
7:45integument upward and if it doesn't kind
7:48of recoil and lay back down nicely, it
7:50often is an indicator of dehydration. So
7:53less water packed in that dermis. So
7:56again, your pet can't tell you it's
7:57thirsty.
7:59However, some of the side effects and I
8:02guess
8:03indicators could lie in that outer layer
8:06of the
8:07of the body.
8:09And then this is actually a really neat
8:13image that shows us our sweat pores. And
8:17so again, this is the dermal ridges that
8:19make up our fingerprints and we can see
8:22those sweat glands at those openings
8:24here.
8:27And so the next little bit is going to
8:29go through some different things that
8:30can give us our skin color.
8:32Skin is one of those
8:34organ systems or integumentary system
8:36rather that can tell a lot about your
8:38health and wellness. And so
8:41we're going to talk about some of those
8:42major pigments that give your skin its
8:44color or hue and how we can sometimes
8:48detect some imbalances with your
8:51homeostasis by just looking at the color
8:53of the skin.
8:55So we've mentioned this melanocytes and
8:58so with UV light, melanocytes actually
9:00can increase their activity and produce
9:03increased melanin
9:04and that will cause darkening or
9:07deepening of the pigment of the skin and
9:09it often can then protect the cells from
9:13UV light. And so people with darker hues
9:16of skin rarely get skin cancer. Not
9:19never, but rarely. And so again,
9:22pigmented darker more deeply pigmented
9:25skin is usually going to be more well
9:28protected from UV light.
9:30And so in our lab crew activity, we'll
9:33talk a lot more about melanin and um
9:36skin pigments. And so once again, the
9:39skin tone or color difference is it's
9:41not
9:42um
9:43that one has more or less pigment, it's
9:44just different types of melanin and
9:46different amounts of melanin produced.
9:49And so they have the same number of
9:50melanocytes sitting along that papillary
9:53edge of the dermis, but just have darker
9:55or lighter expressing melanosomes.
9:59And this just shows us a little bit
10:00more. Here's our melanocyte close up and
10:03we can see that melanocytes will make
10:05melanin
10:07and they will um
10:09pack it in these melanosomes. So again,
10:11melano for the pigment melanin, soma
10:14means body, so these small bodies that
10:16they can easily transfer to neighboring
10:18keratinocytes. And so the keratinocytes
10:21that are next door will then express the
10:24that skin tone or hue that is um
10:28again, kind of encoded in that melanin.
10:32And that's again a way that our skin can
10:35protect it itself and other
10:36keratinocytes from UV light or damage.
10:42And then I think I already mentioned
10:43this. So again, if you were to look at
10:44these two micrographs, which one would
10:48be a more more darkly pigmented skin?
10:50And it would be this one where you can
10:51see the darker melanin expressed in um
10:54slide A as compared to slide B.
10:59And then other skin pigments, one is
11:01carotene. So carotene is actually um
11:04packed in
11:06vegetables such as um sweet potatoes or
11:09carrots and it provides a yellow or
11:12orange pigment that can accumulate in
11:14the stratum corneum and the hypodermis.
11:17And it can give our skin sort of that
11:18yellow tinge. So sometimes you'll see
11:20babies that eat a lot of carrots that
11:23around their nose sometimes looks a
11:25little orange because of that.
11:27One of the important skin pigments is
11:29hemoglobin. So hemoglobin is one of the
11:32few proteins that actually has a color
11:34to it. Um
11:36and so, it is red if you were to um
11:39isolate hemoglobin on its own and run it
11:41on a gel, for example, you could see it
11:43because it has a crimson color. And so,
11:46oxygenated hemoglobin is much more
11:48deeply red as opposed to um
11:53hemoglobin that has been
11:55deoxygenated or lost some of the oxygen
11:58um molecules. And so, that would be a
12:01more blue um or deeper
12:04tone of red.
12:05And so, just by looking at someone who
12:08for has exercised recently, for example,
12:10you can tell that their face um and
12:13their skin has a more pinkish hue. It
12:15demonstrates richly oxygenated blood
12:18that's passing a uh nearby the dermis.
12:22Whereas people who are um having a
12:25trouble either with their respiratory
12:27system or their cardiovascular system
12:30may show more of a blue hue to their
12:32skin and that indicates that hemoglobin
12:34is not fully oxygenated and it may be an
12:36indicator of um
12:38a homeostatic imbalance.
12:41And so, the term for that is cyanosis.
12:44It means when the skin looks blue,
12:46meaning that there's poorly oxygenated
12:48hemoglobin. This is a pretty significant
12:50example in this patient here where you
12:52can see the fingertips are blue. And a
12:55lot of times the extremities are um
12:57preferentially
12:58affected by that blue tone because your
13:02body will spare
13:04um blood supply to your extremities in
13:06order to preserve it for your heart and
13:08your lungs and your brain. And so,
13:10again, that blue hue is sometimes an
13:12indicator of issues with either
13:14cardiovascular health or respiratory
13:16health.
13:18Erythema means redness. So, again, we
13:21hear that erythro
13:23um or red in erythrocyte, which are our
13:26red blood cells. And so this just we
13:28might experience due to embarrassment or
13:31allergy. So again, our nervous system
13:33gives us away um in lowing blood flow to
13:36come to our face, for example, if we are
13:39embarrassed. So again, our emotions um
13:41can affect the color of our skin.
13:44We see that also with pallor, which is
13:46where your skin turns white, potentially
13:48due to fear or anemia. So again, if you
13:51have low oxygen carrying capacity on
13:53hemoglobin, um whether you have a
13:56hemoglobin uh mutation such as you might
13:59find with sickle cell anemia, the color
14:01of someone's skin is not as red
14:04um
14:05or as
14:07richly um oxygenated and so it's more
14:10white.
14:11And then jaundice. Jaundice is usually
14:13an example or an indicator, rather, of
14:16liver dysfunction. So if um bilirubin,
14:19which should be processed by our liver,
14:21builds up, our skin takes on a yellow
14:24hue. Sometimes eyes also take on that
14:27yellow hue. And so you can see this in
14:29this picture here of a baby who um
14:32sometimes when babies are born, their
14:34liver isn't functioning fully properly
14:36yet and they build up bilirubin and
14:38their skin looks yellow.
14:39Fortunately, it's an easy treatment.
14:42Phototherapy can convert bilirubin to
14:45its um active form and now the skin is
14:48back to its um
14:50its typical hue.
14:53And then finally, black and bruise. So
14:54if you were to bruise yourself, I feel
14:57like everyone pretty much knows what
14:59this would look like. You might have
15:00blood vessels in your dermis that break
15:03and blood accumulates under the skin.
15:05And again, it'll take a little while to
15:07heal, but it will resolve on its own.
15:10All right, I'm going to stop here and
15:12continue on with a new clip.