Animal Tissues

Hi. In this video, we're going to talk about the basics of animal physiology and cover the major types of tissues found in animals. Now, anatomy is the study of an organism's physical structures. Very famous. Studying anatomy is this image here, The Vitruvian man, drawn by Leonardo da Vinci Physiology is the study of the functions of those structures. So here you can see the human cardiovascular system, which is a network of veins, arteries and capital Aries. And, of course, the heart, those air, the structures, the function. The physiology of this is to pump blood, and mainly to get oxygen to deliver oxygen to tissues in the body by pumping the blood around. So there you have that difference between anatomy and physiology. Now organisms are going to have adaptations that they acquire through evolution. These were going to be in traits that are they're able to pass down to their offspring heritable traits that will improve their chances of surviving and reproducing in their environment. One of my favorite all time examples of an adaptation is with these maws behind my head. You see, Prior to the industrial Revolution, most of this species of moth appeared like this. They were white. The industrial revolution in England brought on tons of smog and pollution and generally darkened the air and, ah, stained dark. You know, just the environment around these factories. And so over time the population of moths shifted from mostly having this white appearance to mostly having this black appearance. And the reason for that is these white mods stuck out like sore thumbs in the post industrial world, making them easy targets for predators, meaning they had a lower chance of surviving and a therefore a lower chance of effectively reproducing. So now this species of moth is mostly in this appearance, or mostly has this appearance. Now these adaptations should not be confused with acclimatization, acclimatization, zehr short term, um, basically short term adaptations to changes in the environment. These are going to be things like, uh, the amount of oxygen that your red blood cells can carry. I mean, it was the famous example. Lots of runners want to train high altitudes because the thinking is by training at high altitudes, they'll acclimatized to the high altitude and they'll their blood cells will be able thio, suck up more oxygen and therefore they will be able to deliver mawr oxygen to their tissues. The problem with this is as soon as these runners go back to normal lower altitudes, they're gonna lose this effect. It actually goes away so quickly that it's in some respects, almost not even worth the trouble. So, uh, adaptations, they're gonna be long term passed down through generations. Acclimatization happens within an individual in a short span of time. Now, the thing about evolution is it's not going to lead to perfect adaptations. There's this idea called fitness trade offs, which is essentially a limit to an organism's ability to adapt to its environment. And this is in part due to a finite energy capacity. Essentially, an organism has Onley. So many resource is it can commit, right? I really like to think about this. If you've ever played a role playing game, right, your character has different stats. You can Onley commit a certain number of stat points, though, right? You can't make your guy really, really strong and really, really fast or something, right? You only have a set number of resource is that you can allocate well. The same is true with adaptations, organisms can't make everything perfect because they only have a finite resource pool to draw from. So what you get is essentially a cost benefit compromise for the energy investment in adaptations. Basically, you want to expend the least amount of energy for the biggest effect now adaptations air also going to be limited by existing A. Leal's and ancestral genes and organisms can Onley modify or really only work with the genes that came before the genes that are available to them, So that's going to constrict the possibilities in terms of an organism's adaptations. For example, our spines are actually terribly designed for us standing upright. That's why basically all humans have back problems. The reason is we weren't intended to be upright creatures. The spine came from creatures that walked on all fours. But that was our constriction, right? Those were the confines within which we had to work. So you got to live with the back problems. Now there's also a trade off between the reproductive success of an organism and its chance of survival. You know, Uhh. The way I like to think of this is if you commit too much toe having one successful reproduction you might actually be losing out when you could have had to mildly successful reproduction periods. So I guess what I'm trying to say is, sometimes it's more important to ensure the survival of the organism so that they can reproduce another day than to just commit all the way to just getting that one reproduction done. Uh, you know, one of the ways this often comes up in terms of survival is the immune system. You know, it takes a lot of energy for animals to mount an immune response, and sometimes it's worth it to sacrifice reproduction in order to ensure the organism survives and again can reproduce another day. So, yeah, you know, basically what this all comes down to is if a mutant Lille altars of feature in an individual, and it allows that individual to survive and reproduce more efficiently that alil is going to increase in frequency in the population. This is getting back to that idea of Hardy Weinberg population genetics with the frequency of genes appearing in a population, you know, the idea is that if an individual survives and reproduces more effectively, they're going to have more offspring that have that mutiny, Lille and those offspring are going to survive and reproduce more effectively. So they're gonna pass on that Alil. So it's going to become more prevalent in the population. Now. Just it illustrate this idea of fitness tradeoffs with some real world examples. I want to talk about the Cheetah. Now, Cheetahs are known for their ability to run super, super fast. And the way this actually works is if their legs air longer. They're able to actually run faster, but they only have a finite resource pool. Right. If you make the legs too long, the bones are too brittle. The cheetah will risk breaking its legs all the time. You don't want to make the legs too short, because then it's not gonna run fast enough. So you need to find this cost benefit compromise the longest you could make the legs while the bones air still sturdy enough that the chief is not gonna risk breaking its leg every time it prints after gazelle or whatever. Another beautiful example of this also with another animal from Africa. The giraffe, as you can see here. And as I'm sure you know about drafts, they've got this really crazy long neck, and part of the reason for that is they're able to reach vegetation that's higher up than other herbivores can reach. Right? They could get. They could eat the vegetation that's in the treetops that other or other herbivores can't get to. This allows them to survive more effectively because they don't have to compete with a bunch of other organisms for food, right there, really kind of just competing with drafts. Other dudes you can reach all the way up there. Here's the problem. That neck is really big and really heavy and really energy expensive to make. So you know you could have the best neck in the world, but that's not going to be efficient. You want that cost benefit compromise. You want the neck to be just long enough that it can reach that vegetation, and the organism will easily be able to secure food we're at. At the same time. It's not going to waste tons of energy in having you know an overly long neck. I mean, just think about the amount of muscle in there alone and all the energy demands that muscle has just to keep the organisms head up. So with that, let's flip the page

in living systems structure is always related to function. There's no room to waste energy on things for frivolous reasons, and you can see this relationship between structure and function all the way down. At the molecular level, consider a membrane protein that needs to span the hydrophobic plasma membrane, yet interact with the Hydra Filic environments inside and outside the cell. Also. Ah, lot of these membrane proteins, for example, transport ions, which are charged molecules, right, are charged particles. I mean now with the membrane protein, it's going toe have hydrophobic regions, right. Those hydrophobic regions, they're gonna interact with the membrane and in part anchor it into the membrane. And it's going to have Hydra Felix regions which will interact with the intracellular and extra cellular environment. And assuming, for example, it's transporting an eye on it will have a hydra filic internal environment to get that charge particle through. We also see this relationship between structure and function. At the cellular level. Consider cells that perform secretion right. They need thio export lots of molecules. What is the organ l involved with exporting stuff? Golgi. Apparatus. Well, here you can see a nice electron microscope view of a cell that is chock full of Golgi apparatus. All this fold e stuff here is Golgi apparatus. And that's because this is a secretary cell, a cell that plays a role in secrete ing substances in the body. So it's gonna be chock full of Golgi apparatus to carry out that function efficiently. And of course, we see this on the organ, the whole organism level as well. Uh, the famous example, of course, being the flower that Darwin saw, which you can see right here. And this flower has a really long tube. It's kind of hard to see in this image, but just take my word for it. This tube that leads to the nectarine, the nectar producing portion of the flower, can be almost a foot long. And when Darwin first saw it, he said, You know what? I bet there's an animal out there that has a proboscis cas that can reach all the way down there and get that nectar. And there it is, this moth right here with this huge proboscis Cus, you can see it uses to feed feed on nectar from this flower, so structure is going to fit function Now, when we talk about on organisms, anatomy and physiology, we're gonna be talking a lot about tissues and organs. A tissue is going to be a group of cells that carries out a specific function, and here you can see a sample of some tissue from a lung. Thes cells that are stained in this color are, um, are part of a tissue. They're going to carry out a specific function, and they're gonna work in concert with other tissues in lung to, you know, carry out the function of the lungs to you perform gas exchange. Ah, the lungs themselves are in Oregon, which is basically composed of multiple tissues and will carry out some specialized functions. So, for example, in the lungs you need tissues where gas exchange can occur. There's also tissues that produced, uh, mucus substance to help prevent the lungs from collapsing. There's a lot of stuff that goes on to just carrying out that one specialized function of the organ. It takes multiple tissues working together, and then those organs will actually work in concert with each other in what we call organ systems. This is a group of organs that works together to carry out some function, right? So while the lungs might perform gas exchange, they need other structures to carry out the function of breathing. So let me jump out of the way here and here. You can see the respiratory system. This is the organ system responsible for breath. And you can see it has multiple components of which the lungs, these guys, which you can see in pink over here, the lungs are only one Oregon in this system, right? It requires many other things working in concert to accomplish the job. So with that, let's turn the page and talk about tissues.

tissues or complex structures made of highly specialized cells they don't form overnight. In fact, an organism begins to develop its tissues early on in embryo development, following what's known as Gast relation After gassed relation, thes cell layers called germ layers develop these air kind of like embryonic tissues. And there's three types the outer layer or the Ecto derm. The internal cells, which are called the miso Durham, and the internal sell are the innermost cells. Rather, the Endo Durham, and you can see those depicted in the gas strolla here. And if you don't remember what a gastro Liz, I recommend you go back and check out our video on development that covers this whole process of blast elation and gassed relation and talks about how you get to a weird ball of cells like that. Now adult tissues come from these embryonic tissues, and there's four types of adult tissues. You have nervous tissue, which will come from the Nicoderm and muscle tissue, which comes from the miso Durm connective tissue, which also comes from the miso Durham and epithelial tissue that comes from both the end of term and the extra term. Depending on what type of epithelium you're dealing with. You can see some examples of the sort of final products of these germ layers and what they'll wind up as right here with that, let's turn the page.

connective tissue plays a major support role in the animal body. It connects, separates and cushions other tissues and is basically made up of some cells scattered within extra cellular matrix. Extra cellular matrix. Hopefully you remember is an array of proteins and this gel like substance called ground substance. And this functions as a support structure outside of eukaryotic cells in order to kind of play the role that a cell wall might, for example, that has a lot of other properties to. But you can think of it as a sort of surrogate cell wall. Give structural support Now. Loose connective tissue is the most common type of connective tissue found in vertebrates. It helps hold organs in place and attaches epithelial tissue, which is something we're going to talk about in just a moment now. Most notable type of loose connective tissue is at a post tissue or fat adipose. Tissue is mostly made up of these cells, called adipose sites, or that sells, and you can see an example of loose connective tissue. Here in these two images, these air both loose connective tissues. Now another type of connective tissue is dense, or sometimes it's called fibrous connective tissue, and this tissue is dense with collagen fibers. Uh, most notable are most notably, it's what makes up tendons, which connect muscle to bone, very important, and ligaments which connect bone to bone. Also very important. That's how your body moves. And you can see an example of this fibrous connective tissue right here above my head. Now, you also can have supportive connective tissue, and this is stuff like bone and cartilage, and these tissues provide structural integrity. You can see examples of bone and cartilage here. This is bone and right behind my head you have some cartilage these tissues form and a hard extra cellular matrix, which is what gives them that structural integrity. Lastly, there's fluid connective tissue, and this is basically blood. Blood cells have a liquid extra cellular matrix we call plasma. And here you can also just see a nice little example of how connective tissue functions with other tissues. The stuff stained in blue in this image is connective tissue, and this purple stuff that it is surrounding is a type of epithelial tissue. So you can see how the connective tissue here is supporting that epithelium now nervous tissue. Very important stuff, right? This is Well, this is how I'm thinking these thoughts and speaking to you right now, this tissue conducts electrical and chemical signals and is divided between the central and peripheral nervous systems, which we'll talk about when we discuss the nervous system in general. Now, the main type of cell that gets all the credit in the nervous system is nervous. Tissue, rather is our neurons thes receive and transmit the electrical signals. You can see a neuron here. This is a neuron. And it, uh it transmits these electrical signals by transporting ions across the membrane in what we call the action potential. We will talk about that again when we cover the nervous system. The main components of a neuron are the ax on, which is this portion here. That portion is the ax on, and he dendrites this branch stuff out here that I have circled. Those are the dendrites. Now the ax on you can kind of think of as the wire. This is the structure. It can be very, very long sometimes. And this is what transmits that electrical signal. The dendrites thes branch structures are what received signals and kind of figure out how the cell needs to respond to them now. The reason I kind of talked about neurons like they get all the attention, but they don't deserve it is because of these other cells in nervous tissue. Goliath Goliath do not get nearly enough credit. They're super super important. They, in fact, are support cells for neurons essential to their survival. Neurons would not live without these Goliath, and they also help the neurons with their functioning. And we'll get to the specifics of their roles when we talk about the nervous system. But let me just say that this beautiful Astra site that my head was covering this Goliath right here is probably responsible for much more of the functions of the nervous system than it actually gets credit for. A lot of current research and neuroscience is showing that glia playing much more important role than their initially given credit for, and they actually are also involved in signaling, albeit in a different way from neuron. So super important stuff don't write off glia. All right with that, let's turn the page

muscle tissue is unique to animals and is capable of contraction. That's how animal locomotion works. There's actually three types of muscle tissue that we'll talk about these air skeletal muscle, which is attached to bone and used for locomotion and posture. And you can see right here we have some skeletal muscle. Then we also have cardiac muscle, which you can see right here. This is cardiac muscle on Lee found in the heart, and its job is to contract the heart and pump, help the heart pump blood, and it xgo out some super interesting features that relate Thio signal transaction in like the nervous system, since I'm getting ahead of myself because I'm excited, but we'll get to all that in the later lesson. Lastly, we have smooth muscle. This is found in the walls of organs and vasculature and is what allows them to contract, and you can see some smooth muscle right behind my head here. Boom, smooth muscle. Now the last type of tissue that we'll talk about is epithelial tissue. This lines, organs and body surfaces, and its main job thing that makes it so important is it conception rate, interior and exterior environments. This allows organisms to create unique environments which allow for some drastically different chemical and physical conditions. This is super important. I mean, think about it. Your stomach is full of acid, right? You need that for digestion. But obviously, if that stuff leaked out into your body, you would be done. Zo. Thankfully, we have epithelium that will line are stomach and keep those. Keep those environments separate. You can see an example of epithelial tissue right here. This darkened line that crosses through them is meant to represent the barrier that they create between the two environments. And there's a little bit of terminology that you should know. The a pickle side of the epithelium faces away towards the exterior environment. So here we have our a pickle side. The basal side faces the interior of the animal or the Oregon, for example. And lastly, there is a special type of extra cellular matrix on the basal side that epithelium sit on. This is called the basal lamb Inna, and you can see a nice image of it here. We're looking at a small portion of the exterior or the sort of outer edge of a cell here. This is the inside of the cell. This is the outside of the cell. And this dark wine right here is that Basil, lamb, Inna, that the epithelium will sit on. That's all I have for this lesson. I'll see you guys next time.