hi everyone this lesson is called cells tissues organ systems and it focuses on this idea that there is a hierarchical structure within multicellular organisms so in this diagram that I've got here you can see a multicellular organism and this lesson is all about how a group of cells of like Form and Function can aggregate to form tissues so here we've got examples of muscle cells producing muscle tissue nerve cells producing nerve tissue and so on and so forth and then different tissues combine to form organs such as the kidney organs can then work together and produce a system such as the urinary system or expiratory system and then when we have a group of systems all working together in cooperation we can produce an organism so those levels that we've just talked about cells tissues organs and systems are what make up the hierarchical structure within a multicellular organism so obviously we'll start off by looking at cells now I want you to have a look at the group of different cells I've got on this page and try and work out what type of cells you think they are now the first ones we're going to look at uh this example here now these are red blood cells or rbcs hopefully you uh guess those correctly and another type of cell that you can see here are white blood cells okay down here we have an example of a nerve cell and here some of you may have seen these before these are cheek cells which because they are surface cells in an organism we call these epithelial epithelial cells okay now what I want you to imagine is that all of these cells have come from the same multicellular organism and what you should be able to see that all have in common is the nucleus you can see the nucleus of the nerve cell the nucleus of these cheek cells and you can't see them in the diagram but each of these blood cells will have a nucleus also now because as I said these have all come from the same individual that we consider them to be genetically identical because they will all have an identical copy of the genetic information the DNA now that brings up an interesting point because what you should notice about all of these cells is that they all look completely different to one another so although they're genetically identical they look completely different so they have different structures and they also have different functions so we've got a situation where we have cells with genetically identical information which have differentiated which means they've become specialized to carry out a specific function and have a specific structure whilst they still have the same genetic information and that is a process called differentiation just write that down here differentiation it's a big word and basically what that means is that the cells become specialized so that they have specific structures and functions now why that happens is so that they can obviously carry out their particular job throughout the body how that happens is that whilst they all contain the same DNA it's the it's the genes which are switched on in those cells which lead them to differentiate into the particular typ so in a red blood cell the genes for being a red blood cell have been switched on the genes for being a white blood cell in a red blood cell are not switched on and the genes for becoming a nerve cell in a red blood cell are not switched on and an epithelial cell likewise or vice versa in a white blood cell we have white blood cell genes which are activated and all of the other genes that it contains to become that tell it to become a different type cell are not activated so we call that differentiation and that's why we can have lots of different cells with different structures and functions which are still genetically identical within a multicellular organism okay so now we're going to look at tissues now remember we spoke about earlier tissues are formed when cells with similar structure and function group together as you can see in these examples now there's four different types of tissue in this on this slide connective tissue epithelial tissue muscle tissue and nervous tissue and in this lesson I'm going to focus on these three so I'll just cross out nervous tissue okay because I'm only going to focus on connective epithelial and muscle in this lesson so this slide looks at some examples of epithelial tissue now you would have heard me say earlier that epithelial simply refers to the fact that it is on a Surface so we're looking at surface tissues here for example our skin or the lining of our internal organs now the three types of epithelial tissue that I'm going to talk about uh those three types are squamous bit of a funny name uh columna and ciliated and I've got examples of all three of these in my diagrams just here so squamous cells form squamous epithelial tissue and you would find squamous epithelial tissue on places like the Oli in the lungs or the capillaries in the circulatory system and if we're describing the structure of a squamous cell making up squamous tissue well as you can see they're relatively flat cells next example are columna epithelial tissue cells and there's an example of those here in the diagram and as the name suggest they are long and thin like a Roman column and that's where they get their name from and the last uh sorry column the cells would be found in places like the small intestine or the nephrons of the kidney and the last example are if cells are ciliated and CIA as you can see here refers to these little hairlike protrusions which you can see and we call them cilia the their role if you haven't guessed yet is to increase the surface area of the cell we find ciliated cells in places like the trachea and the oviduct in females and if I was to show you some cated cells in this example on the squer cells I would just simply draw the cyia on the surface of these cells so for cells to be ciliated it just means that they have these hairlike protrusions and remember the purpose of Cil of cyia is to increase the surface area of the cell okay connective tissue is our next example and the role of connective tissue is to hold other tissues and organs together and I've got diagrams of two of the examples here the first example is an interesting one this is bone tissue now bit of a common misconception I've just got a bone here is that bone is not made of cells well that's a misconception bone is made of cells and if I was to chop this bone in half and then we looked at it from that angle there what we would find is if we looked at it under a microscope and zoomed in really close it would look like this and we've got these bone cells okay so bone is a tissue it is made of cells uh just something that happens is the bone cells secrete a form of salt and that salt uh leads to the structure being very solid and that's why Bones have their strong structure which we see and probably the reason why there's a misconception that they're not made of cells because they're so solid and strong but in fact they are uh other example that we've got here is of fibrous tissue and you can see where it gets the name from because although this is all made of these cells it's sort of long thin fibers and it has the same strength as the bone tissue however because it doesn't have that salt that solidifies and forms the the strong compound it's uh a lot less it's a lot more flexible and is able to form uh our tendons and ligaments which either hold bones together or connect muscle to Bone so just going back over those examples we have bone tissue in this example and fibrous tissue in this example the last example is called adap tissue for which I do not have a diagram I'm sorry but adose tissue is involved it's fat tissue basically it stores fat droplets and therefore this tissue performs the roles of insulation uh protection and energy storage okay so that summarizes this slide on connective tissue remember that connective tissue holds other tissue and organs together and the three examples are bone tissue fibrous tissue and adose tissue the last tissue example that we're looking at is muscle tissue now I'm sure we already know that the contraction and relaxation of muscles is what results in movement now there's three types of muscle tissue that we're going to look at cardiac muscle sceletal muscle and smooth muscle so each of those tissues are made up of their specific type of cell first example cardiac muscle tissue cardiac is a giveaway that we're obviously talking about the heart now cardiac muscle tissue is very special for two main reasons the first reason is that cardiac muscle tissue does not fatigue and you'd be aware of that due to the fact that you are still alive your heart has been continuously beating for your whole life and it hasn't gotten tired luckily and the other thing about cardiac muscle tissue is that it it continues to contract and relax uh and it's involuntary and which means that you don't consciously control it and you can't make it stop if you want to and you can't speed it up if you want to uh it it's controlled by nerve messages and it's it's all uh coordinated by uh special processes okay second type of muscle tissue is sceletal muscle tissue which is the one that I'm sure we're almost familiar with they are the muscles which are attached to our bones via tendons and such examples are the biceps and the triceps etc etc uh they are the ones that are involved with movement of our bodies by contraction and relaxation and the last example is smooth muscle tissue which is probably one that you're not very familiar with smooth muscle tissue lines the walls of our intestine and our blood vessels Our arteries it also lines the walls of some of our other internal organs and its purpose is to help to move food through the intestine by Contracting and relaxing or to help pump blood through the arteries by Contracting and relaxing and it has a bit of a different structure to sceletal muscle and that's indicated by its name it's it's smooth and it's flat and thin and it's as I said lines the walls of the intestines the blood vessels and our other internal organs so that's all of our muscle tissue tissue examples cardiac muscle tissue sceletal muscle tissue and smooth muscle tissue right so so far we've looked at cells and lots of the different types of cells that can differentiate within a multicellular organism we've looked at how cells that are the same type so muscle cells can group together and form muscle tissue or epithelial cells can group together and form epithelial tissue so the same cells have to group together to form tissues but now we're going to look at organs now a definition for organs are discrete structures composed of several types of tissues that perform specific tasks and I'm giving you three examples in this page they are the intestines the heart and the lungs and a key thing that I mentioned was that or orans are composed of several different types of tissue so tissues are only made of one type of cell all group together but organs are made of lots of different types of tissues for example the intestine is made up of epithelial tissue obviously on its surfaces connective tissue smooth muscle tissue which we talked about that lines the uh surface es to help to push the the food through and nerve tissue to help transfer messages the heart is an organ that is composed of fibrous tissue cardiac muscle tissue which we talked about earlier epithelial tissue lining the surfaces and nerve tissue because the nerve messages are what stimulate the heart to beat the lungs are made up of connective tissue smooth muscle tissue epithelial tissue on the surfaces particularly inside the Alvi and lining those alola walls and nerve tissue again so that's a quick summary there of organs remember the definition is an organ is a discrete structure composed of several types of tissue that perform spe a specific task and we've given you three examples the intestine the heart and the lungs and our last slide focuses now on systems this is where we've got to the definition for a system is a group of organs that coordinate to carry out a specific function and it is a requirement that you are able to list the organ systems that constitute the human body so I've included a diagram here of all of them and the first one that I'm going to talk about is the sceletal system now in my definition I'm actually going to combine both of these two the sceletal and muscular system the sceletal system is made up of the major organs of the bones and the muscles so that's makes up its uh its structure or its organ composition and the function of the scal system is obviously for support of the body and movement of the body okay next system is the circulatory system the circulatory system is composed of the heart and the blood vessels and the blood obviously the function of the circulatory system is transport around the body it's our mechanism of getting oxygen in and around the body carbon dioxide out of the body and it all also helps us to remove waste and to get nutrients into the body also the digestive system the digestive system is made of several organs the stomach liver pancreas small intestine and large intestine all located in this region here so several organs combining together to produce this system its role or its function is the digestion and absorption of nutrients which comes from the food which we eat the urinary system which as I explained earlier I refer to as the excretory system the excretory system is made up of the skin the kidneys and the lungs also for removing waste products it's the excretory system it's responsible for excreting waste products whether that waste be Ure which is excreted through the urine or carbon dioxide which is exhaled via the lungs they are the processes that occur via the excretory system next system is the nervous system which is down here in the bottom left hand corner the nervous system is composed of the brain the spinal cord and the nerves so they're the organs involved and the job of the nervous system is communication throughout the body and control of the body things like talking and moving are things that are controlled by nerve messages and they're all coordinated by the brain and the spinal cord okay the reproductive system the reproductive system we've got two different symbols here that's because we have different reproductive systems in males compared to females the reproductive system is made up of different organs depending on male or female testes ovaries and genitals and the purpose or the function of the reproductive system is obviously reproduction a really important system for the survival of the species this system on this diagram is called the lymphatic system uh but I actually refer to it as the immune system the immune system is what keeps us healthy it's made made up of things like the spleen and the thymus the lymph vessels and the lymph nodes and the immune system is responsible for the defense of our body so the immune system will detect any foreign pathogens in our body and it will develop antibodies to destroy them and stop us from getting sick obviously an important one to left the endocrine system the endocrine system has uh another name which you might want to remember it as the endocrine system is basically the system that controls hormones so when you think of endocrine system think hormone system and you see here the symbols there's a different endocrine system for males and for females and that's because there are two different hormones produced in male and females testosterone for males and E Esten for females uh the organs involved in the endocrine system are the endocrine glands which produce hormones and they're found throughout the body the function of the endocrine system is regulation and control it's has a similar function to the nervous system in that these are the two systems responsible for controlling processes that occur throughout the body the difference between the two is that the nervous system sends very fast and shortlived messages via electrochemical impulses whereas the endocrine system sends slower but longer lasting messages via hormones which are chemical messages that travel in the blood last system is the respiratory system which I reckon you're probably familiar with the respiratory system is made up of the trachea and the lungs and the purpose of the respiratory system is for gaseous exchange so we're trying to get oxygen gas into our bodies and into our blood and carbon dioxide gas out of our bodies into the lungs and then out all right so that summarizes all of the systems of the body just recapping this uh presentation or this lesson we've looked at the hierarchy of structure within organisms starting from cells cells of light function and structure that group together and form tissues tissues that can combine to form organs organs that can group together to perform a similar function and form a system and then when we put all of our systems together we can produce a multicellular organism like a human so thanks very much everyone for watching and I'll see you next time time