55: integument

Transcribed by Jazmin Lui May 13 2014

ORGAN SYSTEMS – INTEGUMENT SYSTEMS – DR. WISHE

1. GH TEXT FIG 14-2 THICK SKIN (3 RD ED) Usually I say good morning but we’ve just crossed the hairline of 12:00 so good afternoon. Today I’m going to discuss integument, which you know better as skin. But the scientific name is integument. You should be familiar that the integument that is covered by stratified squamous epithelium. It’s been mentioned enough in other various courses. And there are add-ons or appendages associated with the integument, like sweat glands, sebaceous glands, hair and nails. And it has been estimated that the integument accounts for at least 15% of the total body weight. It becomes continuous with the oral cavity, the lips, it becomes continuous with the eyelids, and going to the opposite end of the tract, it’s continuous with the anal canal. There are variations in topography, colour, and texture. In essence, the geographical landmarks. And this all depends on the amount of vascularity, nerves present, glands, are present, blood vessels, etc. And when you come down to basic terminology. The age of the individual, the race of the individual, the sex of the individual determines what the skin is going to look like. As you look over the skin you’ll find major and minor grooves. The major grooves overly the elbows and the knees and this permits flexibility in terms of muscular skeletal motion. You’ll find wrinkles under the eyes, which the guys don’t care about but you women do, and they’re there normally, not too extensive, but as you get older you get these little puffed up areas or wrinkles. And if you can afford it people have surgery to tighten up the skin and eliminate the excess so your age looks completely different. The minor furrows or folds, are your finger prints, your toe prints, the lines of your palm, the soles of the feet. In terms of functions you really know the integument does. It’s a big protector for injury, friction, pressure, wear and tear. And this particularly applies to thick skin. And that’s what we have on the screen right now. And we’ll go over the layers momentarily.

But this is the thickness of the stratum corneum in terms of thick skin. If you were dealing with thin skin, maybe it would be that thick. Any area where there’s a lot of wear and tear, hard palate, gingival, palms and soles, you’re going to have a very thick layer for the stratum corneum, here’s it’s abbreviated as C. It’s also a protective layer against dehydration, drying out. And you’ve been familiar with if it’s been very hot, you’re been exposed to a lot of heat, steam, you lose a lot of fluid. You begin to dehydrate. And that’s in the winter. But the same thing happens in the summer when you’re exposed to natural sunlight. It dries your skin out. So


putting your face in the sun, as my mother used to say, isn’t the best thing to do. As well as subjecting you to potential squamous cell carcinoma, basal cell carcinoma. It’s just plain gonna dry out that particular area. Protection against bacterial invasion. That’s also an important item. And if you look at your normal skin, it’s protecting you, but if you hurt yourself, you burn yourself, you’re exposing underlying layers of connective tissue. You could pick up an infection, pass it to the blood stream, and get it distributed through the body. Skin is a sense organ. If you don’t believe me, take the palm of your hand and put it on a hot stove. Then you’ll definitely believe me. So it senses heat, cold, etc. The sweat glands release a liquid secretion, and when that happens it’s known as perspiring. And as water evaporates from your body it sort of has a cooling type of effect. It’s sort of your own built in air condition system if you will. Cause as the water evaporates you feel much better. Thermoregulation because of the loss of water is important. And Dr. Schiff will probably come in next lecture and talk to you about thermoregulation throughout the body, and I’m sure he’ll say something about the integument.

The integument has a certain degree of elasticity. That means it can stretch and return to its original shape. There are elastic fibres present in all this connective tissue. If you have some surgery done, or even better, if you’re pregnant, the skin is stretching and stretching. It doesn’t fall apart or rip. That’s because of the elastic fibres. So the skin has a tremendous amount of flexibility in terms of that. Unfortunately as you get older your elasticity tends to decrease and there’s a condition called solar elastosis where you’ve lost a certain degree of this elasticity. If you take the skin on top of the hand, it’s slides back and forth. That’s attributed to the presence of adipose tissue, in terms of the hypodermis. If you grab the skin and pull it up, it should drop down immediately. That means the elastic fibres are working. But if you have to push it down, you’ve lost most of your elasticity. That means you’re climbing the ladder, not necessarily to success, but to bigger and better things. Which you could do without.

The skin is a source of vitamin D so when the sunlight hits the vitamin D it activates it. And there is a term in your handout, you don’t have to know it, dehydrocholesterol or pro-vitamin D. And this is generally located in the bottom layer, your basal layer of the integument. And there are certain enzymes that come along and eventually convert it into a vitamin D kind of derivative. Back to basic tissues, although preferably you may not want to think back that far. Vitamin D is required for proper bone maintenance.


The more bone you have, the more calcium is saved either through the gut or through other means, through the kidney. If you’re low in vitamin D, you get 2 bone conditions. In children what is it called? Rickets. And in adults? Osteomalacia. So the amount of vitamin D is really important. And there’s a certain amount of fat metabolism is going on.

In terms of the layers of the skin, that’s your epidermis. External layer, all ectodermal in origin. If you look at the palms of the hands, again you don’t have to know these numbers, but the thickness of this epidermis could be 0.8 mm. But if you look at the soles what do you think? Would the soles have a thicker or thinner epidermis? It has to be thicker! You’re on your feet all the time. You don’t necessarily use your hands every minute. And then if you compare thick skin to thin skin, skin thin comes in roughly at 0.1 mm. So there’s a big difference in the thickness of the epidermis between thick and thin skin. And underneath the epidermis you have your connective tissue. And don’t forget these epithelial projections of the underlying connective tissue into the epidermis. And what do we call these? Rete pegs. So the thicker the skin, the more numerous and thicker the rete pegs. Because with such a thick stratum corneum you need a lot of adhesive force to make sure it stick to the underlying connective tissue. So interdigitating with these rete pegs are these little connective tissue papilla. And that makes up one of the two layers of the dermis. It’s known as your papillary layer. And once you get past these rete pegs, this area down here really becomes the reticular layer of the dermis. And then the reticular layer of the dermis is where you’re going to find the origin of the sebaceous glands, sweat glands, hair follicles. The connective tissue in both regions is a little different. In the papillary layer it’s areolar CT, in the reticular layer it’s more of a dense irregular collagenous CT. And finally there’s another layer which is not shown in this picture, it’s called the hypodermis or subcutaneous layer which consists of areolar CT and adipose tissue. And then underneath that you’ll find muscle. So the presence of adipose cells allow skin to move back and forth, or slide.

In terms of cell make up, you’re gonna find different types of cells present. Keratinocytes, which accounts for most of the cells, I don’t know why I’ve got so many outlines with me. Langerhan cells which you’ve heard of before, melanocytes, and merkel cells. And we’ll get to each of those cell types eventually. But let’s look at the layers of thick skin. And we could start at the very bottom which is probably the best way to do it.


There’s a single cell layer all the way down here, it’s called the basal cell layer. And that’s the stratum basali. And most of the cells of stratum basali happen to be mitotic cells.

And there’s a certain percentage of melanocytes present as well. In fact the melanocytes could account for 10-25% of cells of the basal cell layer. The basal cells are held together by desmosomes as well as the rest of these layers. And then the base of the basal cell is held to the basement membrane by hemidesmosomes. So there are certain mechanisms in place to keep all these cells together. And there’s a reason for that. Prevent dehydration, prevent bacteria from getting in. So it’s more of a protective nature. And finally if you look at these basal cells, let’s just draw one, there’s usually cytoplasmic process that extends down into the connective tissue layer. So all the epidermal cells held together by desmosomes, the whole arrangement of the integument sticks to the connective tissue, through the presence of rete pegs, connective tissue papilla, and finally the basal cells extend across the basement membrane into the underlying connective tissues. So there are a lot of mechanisms at play here.

Then we have this particular layer right in here, looks a little darker than the rest, it looks a little granular. And that represents the stratum granulosum which is about 3-4 cell layers thick in thick skin. In thin skin it could be down to 2 layers. So the granules that you’re going to find there are keratin hyaline granules. And as these cells move up when the top layer of cells desquamate or slough off, the keratin hyaline granules slowly but surely convert to keratin. There’s other granules present in this layer as well, called lamellar granules, that is believed to be some sort of lipid. That leaks out between the cells and fills up the intercellular space, like a sealant. Again this is all protective in nature.

Then we have another layer which we’ll show you on a different slide, but I’m just going to assume it’s this layer, and it’s the stratum lucida. And the stratum lucida actually looks like a membrane. It has a shiny, glassy appearance. And in this layer the keratin hyaline granules become aligned. This is part of the pathway to keratin. And when the cells finally reach the stratum cornea which is the top most layer, the aligned gets converted into keratin. And depending upon the location, it could be soft keratin or hard keratin, and there’s no need for us to go into the differences between the two. Just realizing that it does exist. Some books an additional terms, and I’ll just draw a little line over here, and that’s referred to the stratum disjunctivum and that’s


the top most layer of cells that’s immediately lost to the environment. As you look at this spinosum layer, even at this low power, somehow it looks like the cells are joined together. They are – by desmosomes. And it was once referred to as spiny cell layer, prickle cell layer, but in reality they aren’t really cytoplasmic extensions. Forming like a bridge between two cells, but really, a desmosome arrangement. And there are spaces between the desmosomes, so the fatty type sealant seeps in, fills up the spaces, and affords the integument a greater degree of protection. As you ascend the layers, even in the spinosum, the cells change shape. Here you could say the shape of the cell is polygonal in shape, multi sided. But as we get towards the granulosum they tend to flatten out and look more like simple squamous cells. And with this thick skin, what happens is with the nuclei, all the organelles die off and essentially you’re dealing with a dead keratinized layer of cells. You can still see cell boundaries but you can’t see anything inside. Ok.

2. J. FIG. 18-2 LAYERS OF THICK SKIN (OLDER VERSION) So the picture on the left is another example of thick skin. Here’s the stratum corneum, stratum granulosum, stratum spinosum and the very bottom layer is the stratum basale. You’ll notice something over here, seems to be spiralling up from the connective tissue, that’s a sweat gland. And the sweat gland actually originates in the reticular layer of the dermis. And it coils and spirals up to the surface. We’ll come back to this picture momentarily.

So we just looked at thick skin, now what about thin skin? Thin skin really covers most of the body. The only place you truly have thick skin – palms, soles of the feet, and if we look at the oral cavity, you will find it as I mentioned before in the gingival, and hard palate. When it comes to thin skin the epithelium is much thinner. So we’ll just draw a little, I’m not doing this too good. But that’s the thickness of the stratum corneum in thin skin. A stratum lucidum is absent. Stratum granulosum is either absence or reduced in number of layers. And that’s why I said thick skin has roughly 4 layers whereas thin skin has 1 or 2 layers of these granulosa cells. The dermis, interestingly enough, is thicker in thin skin. And when you think of thin skin vs thick skin, which part is going to be the sweater part? The palms of the hands and soles of the feet. And you’ll notice it very quickly because your palms are always getting wet and sweaty. And that’s because you’ve got a lot of sweat glands present there. I don’t’ know who your friends are, but I haven’t shook hands with anyone that had a hairy palm


lately. That’s supposed to be funny. Hehe. And the hypodermis tends to be thinner.

Now let’s go into the cells. You’ve heard of Langerhand cells, the part of the immune system. Have you had those lectures yet? No. You have an interesting experience that’s going to make its appearance with those lectures. Langerhan cells are like macrophages. They’re also called dendritic cells. And they come from mesenchyme and it was once believed they were dying melanocytes. But in reality they have nothing to do with the melanocyte. They are antigen recognition cells, or antigen processing cells. So they pick up this foreign substance and sends a signal to the rest of the immune system which now reacts in some sort of fashion to get rid of this foreign material. These cells are not attached to the keratinocytes by desmosomes at all. And I’m sure it must’ve been mentioned in connective tissue, but anything that’s a phagocyte is more or less mobile, or can become mobile and travel through another part of the body. So there are no desmosomes holding it here. And here we have a picture of this cell which they call the epidermal dendritic cell. That’s what we call the Langerhan cell.

In terms of melanocytes, it’s the melanocyte that actually produces the melanin. Up to this point, it’s always been a blast cell producing something. Osteoblast produces bone. A cementblast produces cementum. But in this case there is a melanoblast which then gives rise to a melanocyte but it’s the melanocyte that actually produces the pigment itself. There are various pigments that are normally present in the skin. Oxyhemoglobin is associated with the blood. Keratinoids, the yellowish pigment is present. And then we have melanin. And melanin comes out as a grouping of 5 brown to black granules. Now if you have a lot of pigment, your skin will appear on the dark side, and that’s known as eumelanin, that’s normal. If you find a person with bright red hair, that’s a different type of pigmentation, pheomelanin. Someone with bright red hair, we’re talking natural. Not changed or altered. Look at their eyes. They’re usually light in colour, even to being blue. So there’s a difference in terms of pigment in terms of how it’s distributed through the body. Basically I’m going to make a statement that all integument has some pigment except when it doesn’t. And that’s your albino condition. If you look at an individual that has an albino condition, their skin is literally pure white, the hair colour is really light like light blonde to white-ish. And the eyes, they’re red. That’s because of the absence of pigment. And there’s a whole series of reactions to get to the pigment, the ultraviolet


light hits the cells, and then the cells produce a early stage of melanin, and then there’s a whole series of reaction which lead to the formation of dopa. And then dopa goes through the series of stages in which you finally get melanin. And the way that melanocytes really work, is as the melanocyte moves up through the stratum spinosum, the pigment granules are transferred to all the keratinocytes. So the melanocytes have cytoplasmic processes. And I’ll show you a picture of that momentarily. Did that ok, did that.

Now a person who has very light coloured skin doesn’t necessarily mean they don’t have melanocytes, because the number of melanocytes could be the same in different people. But they appear differently. It’s a matter of how much pigment is produced. Not necessarily the number of melanocytes. People respond to the sunlight differently. If you really have situation where you don’t have to have as much melanin produced, you’re opening up your skin to burning, and you become lobster coloured. But if you keep doing this, sooner or later it’s not going to be to your advantage. Because you’ll come down with things like basal cell or squamous cell carcinoma. Which if you had to get a type of cancer, that’s not bad, because it’s easily corrected.

But then there’s also a condition called melanoma. And the problem with this is that these cells which have mutated spread into the connective tissue and the melanoma is now transported into the circulatory system and can be distributed throughout the body. So melanoma for the most part is very hard to treat unless you catch it early enough. So that’s a much more dangerous type of condition.

So we mentioned albino, there’s another condition called vitiligo. You have a normal amount of pigment but for some reason or another the skin depigments. It loses its pigment. Have you had the lectures on the adrenal gland yet? Somewhere in those lectures it should’ve come out that it depends on what condition you develop, it could affect the skin. And you get all these pigment spots distributed throughout because of the adrenal gland. So nothing is a separate entity in the body. They are all related to each other. This is supposed to be the melanocyte which is distributed between the mitotic cells.

And finally there’s one more cell, this little blue guy here, it’s called a tactile cell. Or it’s called a merkel cell. And I’ve not sure if they’ve decided yet what the function of this cell is but this cell is involved with the nervous system. It might be a support cell


surrounding the sensor. Or it might actually play a role in your tactile sensation. And only if there’s something unusual going, will you find other types of cells in the epithelium. And if there’s something going on, don’t be surprised to find white blood cells, lymphocytes, present in the epithelium. I mean something is happening. And any region in the body, even the digestive tract which has a lumen and is subject to non-sterile conditions, cause the food you’re eating no matter how chopped up it is, it’s not sterile and there’s a possibility of transmission of something from the food. And fairly recently, what was it…oh Costco sells this dried fruit. It’s pretty good. You know apples, it’s a low calorie snack. And one day, couldn’t find it! And afterwards I found out that where it was made became contaminated. Ahh. So they took it off the market. So this is what you’re taking inside of you. So normally you would have lymphocytes migrating to this area to try to protect this particular region from coming down with anything that’s sort of exotic and out of the way.

And this is pretty good. Here’s your basal cell layer, stratum spinosum, your granulosum. And you see sort of a white area, it’s not very thick. That’s the stratum lucidum. And the label’s right over here.

3. GH PLATE 11-1 FIG. 4 THICK SKIN (5 th ED) Here we’re looking at a high power of thick skin. And then in this little rectangle at the bottom right is a lower power. And what you’re picking up is some connective tissue, these epithelial projections are your rete pegs, and you can see this granular layer, that’s the stratum granulosum. And here you see SL. And it appears as sort of a little red membrane, a homogenous membrane. That’s your stratum lucidum. Definitely absent from thin skin and thick skin doesn’t necessarily have to have it. And the rest of the layers here represented by the stratum corneum. And this is a very high power. So you see several layers of cells here, with granules, you think oh those are pigment granules, they’re not. These are the keratin hyaline granules, which eventually become keratin in the upper layers. And these are the keratinocytes. And you can sort of see they’re held together by these little things in between, those are the desmosomes.

4. J. FIG. 18-4 KERATINOCYTES OF STRATUM SPINOSUM OF THICK SKIN (10 TH ED) And here’s a higher power picture A, you can see these, what appear to be little processes between cells. They’re not really cytoplasmic processes but rather desmosomes. Between desmosomes there are some very small spaces. Those are the


spaces that fill up with the fatty granules which act as a sealing zone. This is just a high power of a keratinocyte, and this is even a higher power. And what this is really showing all over here happens to be your desmosome holding your cells together.

5. GH THIN SKIN PALTE (5 TH ED) Picture of thin skin, top layer stratum corneum. This light blue layer with the little rete pegs, that’s your stratum spinosum. And then there’s something in between, probably part of a granulosom layer. From this point down this is all connective tissue, that’s your dermis. And the first part of the dermis is called the papillary layer. And the papillary layer is actually between the rete pegs. It consists of areolar CT. You remember the usually description, very cellular, various cell types, very vascular, etc. And once we get past the rete pegs, extending downward is your reticular layer, and this is more of a dense irregular collagenous connective tissue. Fewer cells, fewer cell types, not very vascular. The fibres are much thicker and they extend every which direction.

This is a hair bulb, hair follicle. Looking at this picture, does this resemble something else we’ve studied recently. A tooth bud! Really. In essence here’s your enamel organ. And the term papilla is used to describe the central part, but here’s your papilla – inner and outer epithelial layers. So in a way your hair follicle develops in a similar fashion. Then the part of the hair follicle that projects above the skin is actually your actual hair. The rest is just referred to as the hair shaft. This clumpy blue thing here represents the accumulation of sebaceous glands. And I know that was mentioned way back in epithelium in basic tissues. And these are the type of glands, they’re holocrine glands, where the entire cell is actually released as the secretion. And the release of the cells is into the hair shaft canal. Sort of an oily type secretion, and depending on how much sebum, that’s what it’s referred to, s-e-b-u-m, it’s release depends or determines how oily your skin is. Or how dry your skin is. And if too much is released it can actually clog the pores of the hair and bacteria could get trapped in there. And then you get like a folliculities. Where there are little afflictions (?) there, it turns white, and that’s because of the presence of your white blood cells, your lymphocytes trying to destroy the bacteria.

And then you have your sweat gland which really has a gland part and the rest of this is your duct. So ¾ of the sweat gland happens to be the duct. And the duct just burrows all the way up and opens up to the surface of the skin. Then they’re showing you this


area as your hypodermis, it’s under the reticular layer, it’s a combination of areolar CT and adipose connective tissue.

6. GH THIN SKIN PLATE 11-2 FIG 1 (5 TH ED) Another picture again of thin skin. This little layer that seems to be popping off, peeling off, is your stratum corneum. And most of the skin that you’re seeing that stains this red/purple colour happens to be the spinosum. If you’re dealing with skin thin is there a need for so many rete pegs? No. you only need it if you need a thick keratinized stratum corneum. So you generally don’t see that many rete pegs. And the same thing applied to the oral cavity as we discuss. Masticatory versus reflecting mucosa. Part of the hair follicle, and we switch to this one, we can see the hair shaft actually emerging on the surface. These are your sebaceous glands, and you see they almost seem to lead into one area right here. It’s like a common duct. And the secretions through the sebaceous glands are released directly into the hair shaft canal. Remember that’s an oily type secretion. And this is pretty good down in this region, it’s almost empty-like, it’s not, it’s got a lot of adipose cells, and that’s characteristic of the hypodermis. And by the way although it’s not clear this is skeletal muscle that’s underneath.

7. J. FIG. 18-3 LAYERS OF THIN SKIN (OLDER VERSION)A higher power once again of thin skin. This is all the cornea that’s sort of lifted off and desquamated. This is essentially your stratum spinosum and finally here we can see a single layer of cells. This is what makes up the stratum basali. A single layer of cells, most of which are mitotic cells, and then there are melanocytes distributed in between. So now this represents your papillary layer of the dermis. Typical areolar CT.

8. J. FIG. 18-6 MELANOCYTES (OLDER VERSION)This is fairly decent, at least picture B. A it’s kind of hard to see what you’re looking at. M means melanocyte. But you and I wouldn’t know just by looking at this picture. Now if you saw something like that, that’s another story. These cells, pink type cells, have a lot of dots or granules in them. That’s the melanin. But then we have this cell which is sandwiched in between. That’s your melanocyte that’s producing the pigment granules and you’ll notice all the cytoplasmic processes. So the melanin exits the cell via the process and then becomes large in the keratinocytes. And this of course is just a TEM picture of your melanocyte and it’s pointing to your granules.

9. J. FIG. 18-8 MELANIN FORMATION (OLDER VERSION)


And here’s a diagrammatic representation which is very nice. You don’t have to know this to this detail, but it’s just for your own information, tyrosine is released, and then is acted upon by an enzyme that’s called tyronsinase. And there’s a whole series of steps leading to dopa and finally to melanin. And this melanin is what’s really going into every process and being carried into a keratinocyte.

10. J. FIG. 18-11 ELASTIC FIBERS IN DERMIS (10 TH ED) This is specifically stained to show you all these elastic fibres that are present in the skin giving skin its elasticity.

11. J.FIG 18-10 TACTILE RECEPTORS (OLDER VERSION)And this is similar to what we saw before. But just a few words about hair. Hair has 3 components: the medulla, a cortex, and cuticle. The medulla is the inside, middle part of the hair. However all hairs don’t have a medulla. But every hair has a cortex. So most of this hair follicle would be made up of the cortex. And that’s where you find pigment and even if there’s a medulla present the cortex is still the major component. And you will find keratin in the cortex. Then surrounding the hair there’s a cuticle. And the cuticle looks like the slanting roofs of a house. So this represents the cuticle of the hair. Then there are several other sheaths. Internal root sheath, external root sheath, and a dermal root sheath. The internal root sheath has a cuticle as well. Except it’s pointing in a different direction. So the 2 layers (watch what I’m doing with my hands) interlock. And that keeps the hair held in place. I mean sooner or later as you wash your hair, hairs do come out, you pull hairs out, whatever. I have to be very careful, there’s not much to spare. And then there’s a continuation of your stratum spinosum and basali. That’s the external root sheath. And what does all epithelium sit on? What’s this structure. BM. Basement membrane. And so the components of the skin extend around the hair. OK.

12. J. FIG. 18-11 TACTILE RECEPTORS (OLDER VERSION)I’m sure you’ve seen this before from Dr. St. Jeanet. Anybody remember what this was called, looks like an onion? PC. Pacinian corpuscle. Has no reference to your computer. What about this one? Ahh you’ve forgotten this stuff. That’s Meissner’s corpuscle. Don’t confuse it with plexus. The plexus is in the gut.so these are all tactile touch receptors.

13. GH PLATE 11-4 FIG. 3 MEISSNER’S CORPUSCLE (5 TH ED) These are pretty good higher powered pictures of again, Meisnner’s corpuscle.


14. J. FIG. 18-12 HAIR (OLDER VERSION)I think that this part is a pretty neat picture. It’s actually an SEM, there’s the pore through which the hair emerges. So this is an SEM of a hair. The rest of this stuff we’ve gone over in better pictures before.

15. GH GRAPHIC PLATE 11-3 (5 th ED) Diagrammatically this is pretty decent for sebaceous glands. And remember they empty into the hair shaft canal. This is actually a bunch of alveoli together. That’s your sweat gland, and then the sweat gland spirals up towards the surface. We’re not going to have anything to say about the nail, etc.

16. J. FIG. 18-15 SEBACEOUS GLANDS (OLDER VERSION)This is pretty vibrant, exuberant. Some more sebaceous glands. Same thing over here. And this is the hair shaft canal. And you can see a piece of hair that’s stuck in the canal.

17. GH PLATE 11-3 FIG. 4 SWEAT GLAND (5 TH ED) Just for comparison these are cross-sections through the sweat gland. And it looks like any other duct, in essence. And we’re going to find a special cell in here. Anybody have any idea what My represents? Myoepithelial cell! So this is widely distributed throughout the body. Different types of glands, your salivary glands, your mammillary glands, and in the sweat glands it squeezes to get rid of the lumen.

18. Cat lampAnd this is a recent acquisition from one of your classmates.


I think this is funnier than the next one.


Now tomorrow I’m doing TMJ and that will be my last picture, it won’t be an animal picture, it’s something to mull over and come to your own conclusion. Till tomorrow.

55: integument

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