6. That Y11 Human Bio Thing - The Respiratory System

Hi and welcome to episode 6 of that year 11 Human Bio thing and in this episode we'll be looking at the respiratory system. Now this is sometimes known as the breathing system and the main organ of this system is the lungs or are the lungs rather and you take air into the breathing system via the mouth or nose usually it's better if you go through the nose because you've got hairs in your nose that can trap any dust or microbes and that's better than going through your mouth and then it passes through the tharynx and then goes down through the trachea and from the trachea it enters into the left or right lung by the bronchai which is plural broncus again like the previous podcast when we talked about the heart as you look at the diagram the broncus the right broncus is on your left hand side and the left broncus is on your right hand side because the person is always looking out at you and these bronchai are divided into smaller tubes called bronchials and the bronchials end in these folded sacs called alveoli singular is alveolus and so we'll be looking at the as I said the breathing system or sometimes known as the respiratory system because it helps or assists respiration in other words you take oxygen in which obviously helps with aerobic respiration and you breathe out carbon dioxide and water vapor. Now the lungs are able to expand and relax but this isn't as a result of the lungs actually move themselves it's as a result of changes in what we call the thoracic cavity surrounding the lungs are into our muscles which are between the ribs known as intercostal muscles and at the bottom of the thoracic cavity you have two sets of muscles called the diaphragm muscles and what happens is when the we're going to talk about breathing in and breathing out. So breathing in is sometimes known as inspirational inhalation and when you breathe in what happens is the muscles between the ribs the intercostal muscles contract moving the ribs up and out. Now on a marking key the word and is always underlined in other words you need both the up and the out then the diaphragm muscle contracts and this moves the diaphragm down or flattens the diaphragm and this increases the space in the thoracic cavity so you've now got a larger volume in the thoracic cavity and it also decreases the pressure as a result of that the lungs expand and air is drawn into the lungs from the outside because the atmospheric air is at lower so it is at higher pressure so it goes from higher pressure to lower pressure inside the lungs and so that is breathing in. Breathing out or exploration or exhalation is when the lungs relax or rather the intercostal muscles relax this causes the ribs to move down and in again the word and is underlined in most marking keys so you need both there's no hard marks there and the diaphragm relaxes as well so it moves up into back into its dome shape and as a result of that the pressure inside the thoracic cavity increases and the volume decreases so air moves out of the lungs as a result and so you make it a question that asks you to compare or contrast breathing in with breathing out and you can contrast each statement for example in inhalation the ribs the intercostal muscles contract move the ribs up and out whereas in exhalation the intercostal muscles relax moving the ribs down and in so that's an example so contrast each statement either as two dot as dot points or in a table which is easy to do and particularly if it's an extended response question. Gas exchange occurs in the alveoli gases that are exchange are oxygen which is more in the there's more greater concentration of oxygen in the air you breathe in then the air you breathe out the air you breathe in contains about 21% and this does vary in different internet sites so in your textbook it says 20.95% but basically 21% the air you breathe out contains only 16% in your textbook it says 15.8% again that can vary slightly the air you breathe in contains 0.04% carbon dioxide some websites were so 0.03% the air you breathe out contains roughly 5% are so 4% and in your textbook it's 4.3% and I have seen some very slight variations on that but basically it's 4% and so they are the gases that are exchanged in the alveoli. Now the alveoli are adapted for gas exchange and you will have learnt about factors that influence the rate of diffusion and the alveoli is where the diffusion occurs so oxygen moves from a higher concentration in the air you breathe in to a lower concentration in the blood that's travelling to the lungs in the pulmonary artery and so that blood is deoxygenated and it has less concentration of oxygen in it so air enters the lungs or rather enters the bloodstream at this point and so the carbon dioxide which is in greater concentration in the pulmonary artery or the vessels travelling to the alveoli is removed because there's more calm dioxide in the blood than there is in the alveoli and so calm dioxide diffuses across the membranes and out through the alveoli and is breathed out so when you breathe in and breathe out we call that ventilation and you get that continuous flow of air into it out of the lungs equally you blood is moving so what we do is by having moving blood and by having breathing in and out you maintain the concentration gradient. Now also the lungs sorry the alveoli are highly vascularized so what that means is that they have a good rich blood supply which allows for this gas exchange to occur because it's able to because it's vascularized the blood is moving the main you maintain that concentration gradient. Also the distance over which the molecule's travel is not very far because the out what walls of the alveoli are only one cell fit and because they're only one cell fit the distance over which the substrates travel oxygen and calm dioxide is very very small. Also the walls are moist and because the moist although oxygen and calm dioxide aren't the most soluble of gases it does increase the efficiency of gaseous exchange because there is some solubility and so that increases the efficiency of these gases being exchanged and the other thing is that the folding of the walls of the alveoli or of the lungs the alveoli increases the surface area to volume ratio so as a result that you get greater amount of diffusion occurring. Two other things to mention about the lungs is that they're found deep within the thoracic cavity and this is important at preventing excessive evaporation of fluid that covers the respiratory surface as we've said the fluid is very important to increase the efficiency of gaseous exchange. Secondly I forgot to mention that the lungs are surrounded by these membranes called pleural membranes which are covered in a fluid called pleural fluid and that's spelled PLEURAL not pleural as in singular and pleural which is spelled PLURAL it's different sometimes they're known that this membrane is known as the pleural and what it does is by releasing this fluid when you breathe in and out the ribs don't rub because it basically lubricates the in between the ribs and the lungs and so therefore you don't get any friction as a result of that which is quite useful. Now I want to have a word about the lifestyle and some of the things that can affect your lungs and not always as a result of lifestyle sometimes because of genetic diseases and so one of those things that you make it is asthma. Asthma is an allergic response to foreign substances that enter the body. Now the substance substances are known as allergens and they cause this allergic reaction they cause like an irritation in your lungs which causes a constriction within the bronchial and as a result that it feels like you're breathing through a drinking straw which is not a good condition to have and some people who suffer from asthma will need to either well they'll have to have an inhaler and in that inhaler there'll be specific drugs that which are designed to relax the muscles surrounding the bronchials and that the idea is that it reduces the constriction the narrowing of the bronchials that allows air in and out of the lungs and people who have asthma many people will take up things like exercise because it somehow alleviates asthma. But that instead you can get stress induced asthma and you can get excise induced asthma as well. Now one of the worst things you could do is smoke cigarettes. I can't emphasize enough smoking very bad don't do it. Smoking cigarettes contain over 300 castenogens over 300 cancer causing agents what is a cancer? A cancerous uncontrolled mitosis and it forms tumors which are a mass of cells that have been formed through mitosis which occurs in an uncontrolled way and these factors can be triggered by a number of things but smoking cigarettes is certainly one of them. Now some people will say well I've been smoking cigarettes all my life and I've never had cancer. I'm 90 years old and it's never been a problem for me but scientists carry out what we call epidemiological studies and we look at the correlation between smoking cigarettes and the number of cases of lung cancer and what you find is that there's a correlation between those things in and it's statistically significant. So basically the more cigarettes you smoke and the longer you smoke for the greater the chances of that you'll have a lung disease of some description lung cancer being one of them. Now the smoke itself can actually damage the cells in your mucous membranes and as a result result of that, it causes an irritation because you have a dry throat, so you produce excessive mucus and you end up with what we call smokers cough. Another major disease is infecema. Infecema is a disease usually caused by long-term exposures to irritating particles in the air taken into the lungs. These irritating particles can damage the alveoli. They cause them to lose their elasticity. As a result of that, the alveoli begin to break down and they no longer increase the surface area to volume ratio, so the rate of gas exchanges a lot less because less elasticity, less gas exchange can occur and the surface area has been decreased and therefore you can't breathe. You have to carry out some voluntary breathing to try and make out for the lack of normal or natural breathing that occurs involuntarily. And so that's not a condition. What is pneumonia? Well, pneumonia is an infection of the lungs caused by bacteria, viruses, fungi or other organisms and the inflammation resulting from the infection causes secretion of fluid and mucus into the alveoli and this reduces the amount of air that the lungs can contain. So this affects the surface area available for gas exchange and if that's reduced then breathing becomes difficult, excuse me as if to emphasize my point. As a result of that, well that is what pneumonia is but notice that there are different types of pneumonia caused by different organisms, bacteria, viruses, fungi and others. Finally I'll just have a word about tuberculosis. What is tuberculosis? Well it's an infection. Usually of the lungs which is caused by the bacteria and mycobacterium tuberculosis. Cases in Australia are particularly low. The incidents are about 1000 cases per year and most of these are in people who have been born overseas. We in Australia are often treated by the low seas by carrying out the vaccine called the BCG and this before that you have a skin test and this will identify if you have any natural immunity to it. Now unfortunately there has been the incidence of isolated incidents of TB occurring even in populations where tuberculosis has been treated but generally speaking if good practices are conducted then the cases of this particular infection remain low particularly in countries like Australia. However, it should be pointed out that it is one of the top three infectious diseases in the world and so we do need to be aware of the wider context or global context. So that's the end of this podcast. I hope you will find it a little bit encouraging to see that it's a shorter podcast than the one on blood and circulation and a little bit less to learn.