On Tissues & Skin
Thursday, October 27th, 2016 10:51 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
amarie24Okay, so I’ve decided that the best way to share what I’m learning in class with you all is to share it after I have my tests. This way, the way I’m organizing the information for you won’t be incoherent and difficult to follow because I’m under a time limit what with my test upcoming. This will allow me to take my time while I work to make sure this makes sense to you. Yay!
So our second test in lecture was on the chapters of tissues and the integumentary system (our skin, hair, nails, etc.). I got a 97 on that one, too! And so here we go, starting from the tissue chapter:
• Our bodies are made up of four main tissues:
1. Epithelium, which covers and protects us (Ex. our skin)
2. Connective, which supports us (Y’know the stuff that surely binds our muscles and skeleton together and, all around that, our skin to those? Yep, that’s your connective tissue hard at work!)
3. Muscle, which allows us to move
4. Nervous, which gives us control (think our brain, spinal cord, nerve endings, etc.)
• Epithelial Tissue
1. You can also call it “epithelium”, and the plural form of that is “epithelia”
2. Our epithelium has a very high level of cellularity, meaning that it’s almost completely made of cells. Think about the general layman’s knowledge of how our skin is constantly sloughing off dead skin cells and our hair is always shedding, yes? That’s ‘cause there are a lotta cells constantly dividing (“actively mitotic”) and hanging around epithelial tissues.
3. Epithelium has special classifications that put them into groups! It’s by the number of cell layers (in some places we only need one layer and, in others, we need more and I’ll explain why soon) and by the shape of the cells
a. If the area only has one layer of cells, then it’s called “simple epithelia”. The parts of our bodies that have this simple epithelia are places like our kidney tubules, [upper] respiratory tract (mostly our trachea/windpipe and nose), and digestive tract (AKA GI tract). And they have only one layer of cells because these are the parts where we need a lotta secretion and absorption. Our body is smart and doesn’t like to make things too difficult; if we need things to pass through via that secretion and/or absorption, then we only want to have to deal with one layer to do it, yes?
b. Now, we have different, special classes for simple epithelia (just like we do for stratified). Uhhh…ya’ll, we have a “squamous epithelium” and from Mrs. A’s notes and the textbook? The main thing I took away from it was that it looks like fucking floor tiles. So…I wrote in my notes under simple squamous “looks like fucking floor tiles”. Indeed, I did. I did.
c. If the area has two or more layers of cells, then it’s called “stratified epithelia”. Now, rub your hands together really hard and really fast for a moment. A lot of us did that in grade school to learn that friction creates heat. But that’s also a great way to learn about and thank your stratified epithelium because it’s those extra cell layers that protect these areas so they can stand up to a lot of abrasion and friction-the palms of our hands and the soles of our feet! So rub your hands together and be sure to thank your stratified epithelium! Wee!
d. Y’know when you gotta pee? Well, your bladder stretches to accommodate that urine until you can relieve yourself and then, as you finally do relieve yourself, it stretches back to its former shape, yes? It’s a stretchy-stretchy organ that does a lot of stretchy-stretchy things for us. For that, we have to thank one of our stratified epithelia, “transitional epithelia”! As its name suggests, transitional epithelia is always changing as the organ it covers is always changing with varying internal pressure (from our urine). Pretty cool, huh?
4. We have a ton of different epithelial glands. We especially have different exocrine glands (have ducts to our body’s outside), which are way, way more common and way, way more diverse than our endocrine glands (don’t have ducts; they just hang out with and sends things directly to our bloodstream). The wildest gland that I found to be is our fucking “holocrine gland”, whose only example in our body is our “sebaceous gland” (they secrete sebum, which gives oil to our hair). This hardcore motherfucker accumulates the product they secrete until they literally rupture and die. And then they’re replaced by the division of underlying cells. Like…what the fuck, holocrine gland. What in all the fuck. That is so freakin’ violent and extra.
• Connective Tissue
1. We have this literally everywhere in our body; it is the most widespread of our four main tissues! Jiggle your arms and your muscles, bones, skin, and tendons don’t come apart! Shake your head, and your brain doesn’t rattle in your skull! Smile as much as you want and your lips don’t detach from your gums! All thanks to that glorious connective tissue!
2. Now, connective tissue doesn’t just connect (bind and support) our body together. It also protects us, insulates us, and transports materials within us.
3. Our “collagen fibers”, one of the types of fibers making up connective tissue, are very tough and they have a lot of tensile strength. They’re found all over our body. And when they’re nice and fresh, they are white. I dunno, but…why are they white? I think that’s so disgusting. Welp. At least when someone says “Imma bust your head down to the white meat”, now we know that they mean collagen fibers. Well…white folks, for you, I guess that would be “Imma bust your head down to the other white meat”, huh? Haha…hah.
4. Y’know when you sprain something? That’s specifically when a ligament is torn or completely ripped off its origin/attachment site. And it hurts terribly, yes? Feels like it’s burning? Well, it feels like it’s burning due to an emergency inflammatory response because when shit gets torn, a lot of foreign microbes/pathogens wanna come to party and fuck shit up even further. That emergency inflammatory response is due to your “mast cells” doing their job. They work together with your “macrophages” who don’t participate in the inflammatory response; they are our Pac-mans, eating any of those dangerous pathogens while our mast cells set flamethrowers to everything. Yeah, I know mast cells make it hurt worse, but they’re just tryna help. They love us; we should be kind to them.
5. Did ya’ll know that adipose (fat) tissue counts as a connective tissue?! It’s true and it does! Our fat is very, very, very important, as it acts as a shock absorber, gives us insulation from cold/prevents heat loss. Yay for adipose tissue!
6. Cartilage Time!
a. Stand up and bend your knees and elbows a few times. You’d think it might hurt because bones are meeting in the places of your knees and elbows, yes? Be like, “Ahh! My bones are grinding together!” But, ideally at least, that doesn’t happen. Now there a lot of different reasons why this doesn’t happen, but for now, we’re going to first thank our “hyaline cartilage”. It’s the most common type of cartilage we have and it covers the ends of our long bones (the bones found in our limbs) and, thus, is one of the factors that keep our bones from grinding when we move. Also, if you tweak the tip of your nose, therein you’ll find were more hyaline cartilage hangs out!
b. Tweak your ear and feel how flexible it is. That’s your “elastic cartilage” at work! You can also find this in your epiglottis, which is a teeny, wittle, very important flap that basically makes sure our food and our air go in the right pipes (hint: it’s the reason you can’t breathe while swallowing).
c. When you bend way over or way back, your spinal/vertebral column doesn’t fall apart, right? And when you sit down, your pubic symphysis, which is the whole structure of bone that gets the bulk of your weight when sitting, doesn’t collapse. And the discs in your knee joints are pretty strong, too, yeah? Thank your “fibrocartilage” for that! It’s compressible and able to resist a lot of tension; I personally liken it to heavy-duty/industrial cartilage, haha. So it’s in those areas of our body where we need a hella lotta support and ability to withstand heavy pressure.
7. Okay, get this…are you ready? Are you ready for this? Our bones are also considered connective tissue! Our bones are also known as “osseous tissue”, teehee!
8. Blood, too, is connective tissue…seriously. This is because blood has the working definition of connective tissue: it has blood cells (our RBCs & WBCs) surrounded by a non-living fluid matrix (our plasma), and then blood itself is the ground substance. Incredible, yeah?!
9. Wanna know what a “cutaneous membrane” is? It’s a dry membrane because it’s exposed to the air. Wanna know an example of that? Our skin! So if you ever want a fancy-dancy name for your skin other than epidermis (which, really, is actually only one layer of our skin), you can surprise everyone with the term cutaneous membrane, teehee!
Onto our Integumentary System!
• It’s not just made of our skin; it’s also made of our sweat and oil glands, hair, and nails! Together they team up to protect us!
• One teensy, teeny, tiny square millimeter of skin has a whopping 70 centimeters of blood vessels, 55 centimeters of nerves, 100 sweat glands and 15 oil glands, 230 sensory receptors, and about half a million cells. Ya’ll, it’s a fuckin’ city in your skin.
• Our skin is made of two layers:
1. The first and outermost is our “epidermis”. It’s made up of those special epithelial cells and is what our naked eyes see.
2. The second, just below, is our “dermis”. It makes up the bulk of our skin and is a tough, leathery layer made of connective tissue. It’s also the only layer that’s vascularized, meaning that it’s richly supplied with blood vessels. This matters because with blood vessels comes blood and with blood come all types of different cells and nutrients and vitamins and minerals and everything in-between. This then means that the dermis gets all of these necessary goodies from our blood and then diffuses them up to our mostly-avascular (meaning without blood vessels) epidermis layer.
• Wonder what anchors our skin with its two layers to our organs underneath? Remember when you shook your arms around and noticed that everything didn’t come apart because your connective tissue is awesome like that? Well, this particular layer isn’t necessarily connective tissue, but it’s our subcutaneous tissue (meaning just below the skin) and it’s called our “hypodermis”. It anchors our skin to our underlying organs while also letting it move relatively freely. Our hypodermis is mostly made of fat; in fact, it holds about half of our body’s fat stores! And since it’s made of so much fat, it also acts as a shock absorber and insulator from cold. Yay!
• Our epidermis is one of the layers of skin, right? Well, the epidermis itself is made of several layers! Five layers in tough skin (simply the palms of our hands and soles of our feet) and four layers in thin skin (pretty much everywhere else on our body). The outermost layer is called our “strateum corneum”, or “corny layer”. So if someone ever says you’re corny, just look very, very seriously at your skin and know that’s the reason, teehee!
• Skin color formation!
1. Our “melanin” is made by cells called “melanocytes”!
2. Now, this is cool and fixed a misconception that I and a lot of other people have: our skin color, be it dark, fair, and in-between, is not determined by the number of melanocytes we have. Why? Because we all have about the same number of melanocytes. The individual and racial differences are due to the differences in our melanocytes’ activities. So the darker we are, the more our melanocytes be workin’ it. Ya’ll pale folks got lazy melanocytes. Nyahahahaha!
3. Love your freckles and pigmented moles. They’re just concentrated areas where your melanin is having a party.
4. And here are chemicals that contribute to skin color formation…
a. The yellow-orange pigment that’s found in the skin of a lot of Asian peoples’ skin is called “carotene”. It works together with melanin and so you have the wide, vast, gorgeous variety in Asian peoples’ skin tones!
b. Now all of ya’ll pasty white folks? Ya’ll have neither much gorgeous melanin activity nor any precious carotene. But you do have a bit of a pinkish hue to your skin, yes? That’s because of “hemoglobin”, which is a crimson-colored, oxygenated pigment in your red blood cells (RBCs) circulating through your dermal capillaries. And because your skin doesn’t have much melanin, your epidermis is transparent and so the hemoglobin color shows through and that’s what makes you rosy-posy.
• Our hair
1. Another, fancy name for our hair is “pili”!
2. And yes, it’s true that our hair is technically dead. They’re mostly made of dead, fused keratinized cells. –sniffles and sobs-
3. The pigment in our hair is also made by melanin, just the same as our skin!
4. “Trichosiderin” is the super-duper special iron-containing pigment that gives people natural red hair.
That’s all for now and I’ll do the bones/skeletal system later on. Hope you enjoyed!
no subject
Date: 2016-10-27 07:10 pm (UTC)>>squamous layer
Ohhhh, so when they talk about squamous-cell somethingorother and look really serious in ads and stuff... they mean your floor tiles got all hecked up. *solemn nod*
>> transitional epithelia
Ooooh, neat! I wondered how that worked...
>>Skin City
... is the name of my new cover band. /rimshot
Also, that is ridiculously cool.
It is so great reading things like this. I'm going to go off the rails for a moment here, because kid!Six was really into Cartesian dualism... the whole body/spirit divide, summed up neatly by Yoda. "Luminous beings are we, not this crude matter." Now, I got some good stuff out of that (like respect for us luminous beings)... but I also got a good helping of disdain for this crude matter, and a few attitudes that really haven't helped me as an adult trying to navigate a physical world in a physical body. That divide, it is deep, and I'm pretty sure there's wolves in the bottom of it.
Well, this crude matter is actually pretty amazing, isn't it?
So every time I read something about how cool bodies are, about how amazing it is that these massively-complex organisms can function at all, never mind a whole fucking century... well, it's pretty awesome.
So, thanks. :D
>>They’re just concentrated areas where your melanin is having a party.
N'aww. Party on, melanocytes!
>>Wonder what anchors our skin with its two layers to our organs underneath?
I did, actually. :D Cool beans! Uh... as a hunter, who has occasionally had cause to skin something... that hypodermis works real hard.
>> here are chemicals that contribute to skin color formation…
Whoa, cool!
A lot of nonhuman animals have two pigments interacting in cool ways - like how a calico cat has grey, red, and white fur. It's really neat to hear that humans have two pigments interacting, too!
.. Does that mean white people are leukistic? *s*
>>nd yes, it’s true that our hair is technically dead.
But if it weren't, we couldn't show off all our cool hairstyles! Thanks for taking one for the team, hair.
>>sebaceous gland
@_@ That's pretty metal.
no subject
Date: 2016-10-29 01:12 am (UTC)Floor tiles...yes, the freakin' floor tiles!!!
Yes, this crude matter, this physical body, really is amazing. Truly and amazingly...amazing.
I had no idea that you hunted! And I certainly had no idea that, when skinning the animal, the hypodermis gives you so much trouble. No idea at all. :O
"Leukistic"...I cannot stop laughing. Nyahahaha!
no subject
Date: 2016-10-29 03:18 am (UTC)Honest question! xD This is the kind of question that gets me looked at funny, particularly when I ask other white people. *snort*
Edit: I did some research and found honestly very little information, but: it seems that generally, the answer is no. Leukism seems to be a lack of pigment-producing cells, and you actually answered that above: we've all got the same amount of melanocytes, just some do more than others. :)
Yup! Skinning is hard. That hypodermis holds on for... uh, dear life? /duck
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Date: 2016-10-29 01:48 pm (UTC)...the hypodermis holds on for dear life. You come into my house and make me laugh so freakin' hard. Yeah, you better duck because a Carebear is coming your way! (Nyahahahahahahaha! Good one! So clever, OMFG!!!)
no subject
Date: 2016-10-28 08:18 pm (UTC)no subject
Date: 2016-10-29 01:02 am (UTC)no subject
Date: 2016-10-30 02:26 am (UTC)I am so glad all my tissues hang together so well and my bones hold me up and my joints move! Knowing how it all works makes it even cooler.