"Listening to the rhythm of this woman's heartbeat is like listening to the rhythm of human life itself" "Its constancy is critical" "Since she was in her mother's womb her heart has unfailingly beat a billion times" "She also has taken a quarter of a billion breaths" "Her lungs and heart work together but they are each part of different anatomical systems" "They each have different rhythm" "To understand those rhythms is to grasp the poetry of anatomy" "Life is like a slow fire" "But, unlike the flickering flames of the fires we are used to, the fires of life burn deep within us" "But in order to keep burning, those fires need oxygen just as much as ordinary fires" "And our body has two systems to ensure that the oxygen those fires need are taken into our body and distributed to its furthest reaches" "We have a bellows - the lungs - which pulls the oxygen into the body" "And we have a pump - the heart, that ensures that that oxygen is distributed to its furthest reaches" "And it is these two systems the respiratory system and the circulatory system that we are going to be describing to you today" "We are going to follow the journey of a molecule of oxygen into the body, round, being burned and back out again." "And we are going to start our journey, therefore, with the bellows, with the lungs." "And in order to show you these, the first part of the procedure that we will be performing is to reflect, that is to peel back the skin to reveal the rib cage." "And I will start with what we call a Y cut, just over the clavicles, both clavicles," "from the left to the right side." "The white tissue is the fat tissue." "Now I will do the middle cut just across the sternum." "It is an advantage that I not accidentally cut too deep and will cut muscles, because there are no muscles just above the sternum." "And I go down here to the naval, I circumcise the naval and then I go to both sides over here, and here to the left side." "Marius will help me and we both will peel the skin away, together with the subcutaneous fat tissue" "away from the rib cage and from the abdominal muscles." "It is essential that I start at the right depth, right from the beginning, not too deep, not superficial." "Only this way I will avoid that at the end, the specimen, the muscles are covered with patches of fat." "This body is fresh, it is not fixed." "We need the flexibility of the organs, lung, heart,vessels we want to demonstrate." "The heart and lungs are placed in the thorax and the thorax is completely encased in the bony rib cage." "Ribs act as a protection for the lungs and the heart, the lung are soft, spongy tissues and the heart is a complicated electrical machine which mustn't be disturbed, so they are both hidden within the ribs, which are just beginning to come into view now." "Another point that is worth making is to do with the colour of the tissues that you are seeing." "You can see that the subcutaneous fat, here, looks a sort of orangey yellow colour, which is the colour that this is in life and the muscles are a sort-of a salmon red colour, there." "These are the natural colours of the tissue and what you are seeing here is unfixed tissue." "So these are the colours that tissue is in a normal human body." "The muscles are covered by a sheet of subcutaneous tissue what you see here is the fat, but also of connective tissue and this actually is called fascia." "The muscle fascia in his fascia you see here, the muscle moves." "So the fascia has been taken here away, but when we take about a couple of hours to do that, then the body should first look like that and a second step I will take away this fascia." "But in a live dissection, where time is pressing, this work has to progress faster." "Performing a dissection section on a fresh human body is nearer to surgery than performing a dissection on a fixed body." "In a fixed body, the connective tissues become tough and firm and the various different layers of tissue become much more firmly stuck together." "Whereas, in a fresh body, the fascial tissues are still quite loose and therefore easier to prise apart from each other, so the dissection work is actually easier for an anatomist in a fresh body than in a fixed one." "I will now show very clearly the borders of the big pectoral muscle, the big breast muscle and I will move the breast muscle in order to expose the thoracic shield with the intercostal muscles, and I just do this now." "Let's do the other side." "So revealing now, the sheet beneath, the layer beneath the pectoral muscle." "What you see here is actually here, the intercostal muscle, exactly here." "The intercostal muscles are two layers of muscle running between the ribs from rib to rib." "So I reflect now the pectoral muscle to the upper side and all the ribs we see now, those strands of fibres and of muscles going from rib to rib, contracting the space between the rib during expiration." "So here we have the rib cage now fully exposed." "You can see the lower borders of the rib cage running down here and the ribs underneath the fascia running in this direction." "And it may be worth, before we go further, locating the lungs on our live model." "And here is Juliet our anatomical artist and our live model today is Lindy and Juliet is just drawing on for us, the position of Lindy's lungs." "Now the lungs can't move by themselves, they have to be moved by muscles of the rib cage." "And, in quiet breathing, such as Lindy is doing now, the main respiratory muscle is the diaphragm this partition between the thorax, which contains the lungs and heart" "and the abdomen." "In quiet breathing, the diaphragm moves very slightly down to pull air into the lungs." "In more vigorous breathing, such as when you are doing heavy exercise, the accessory muscles of respiration, if you do that again, Lindy, if you breathe in deeply, you can see up here at the top of the chest, as well as the intercostal muscles" "and some other of the chest wall muscles aid the diaphragm in moving the rib cage and the expansion of the rib cage that happens when these muscles work, pulls air into the lungs." "So the next part of the procedure that we are going to show you is opening the rib cage to reveal the thoracic organs - the heart and lungs - in their anatomical positions." "I am now about to open the rib cage with this specialised scissor." "I go up to the top, and between the clavicle and the first rib, I cut" "And now, there comes the cuts of the breast bone" "And now, I'm going down all the way..." "Well, there are some adhesions inside, therefore I like to first reflect the sternum by taking apart the adhesions" "between the abdomen wall and the intestine and reflect the whole thoracic abdominal sheet down." "By pulling up, now, the sternum" "I have to cut through this connective tissue, which between the heart, the mediastinum it is called and the thoracic shield stretches." "So if you would pull, please." "So I will cut, now, the diaphragm, which is just below the lung, here." "I will cut the diaphragm away from the rib cage." "All the body cavities have their own linings the cavities in which the lungs lie are lined by the pleura, which completely cover the lungs, except where they are joined to the heart and where the airways come out." "The lining of the heart is called the pericardium the sack around the heart and then a bit lower down, the lining of the abnormal abdominal cavity is called the peritoneum." "Dividing the thoracic cavity - in other words, the two pleural cavities from the abdominal cavity, is the diaphragm." "The diaphragm is now very nicely to see here, it is quite a dome, you know, a dome." "So you can understand how when that domed muscle contracts, it goes flatter." "That pulls it down and expands the pleural cavity which the lung sits in." "The lung is stuck to the outer wall of the pleura a bit like when you pick up a glass that got wet on the bottom and it picks up the cocktail mat underneath it" "Well, the lung is stuck to the outer wall of the thoracic cage in the same way." "So when the diaphragm pulls down, this expands the lung inside the pleural cavity by creating a small vacuum, which expands the lung up." "When the diaphragm relaxes and comes back to this domed position, the lung contracts down again." "The lung is now in expiration and the clavity pushes the intestinal content up to the thorax and therefore, the diaphragm is, as compared to normal life, in expiratory situation." "So, this feels as though there are adhesions here which prompted me to change the dissection technique and to reflect the sternum and..." "So, we have now, reflected the abdominal muscles, together with the thoracic shield downwards." "And what you see, here, are both lungs." "The right lungs..." "..a little adhesions, which is not normal, but happens quite often." "The right lung and here, the left lung," "all just above the diaphragm." "And in the middle, still enclosed in the pericardial sack, which we will open later, is the heart." "Just in here." "There is a heart." "In order to give you a better idea of how the airways work," "I want to show you that over at a plastinated specimens." "So actually, the air and this should be the air, moves into the nose through the nasal cavity," "but also through the mouth." "And both airway meet in the pharynx, going through the larynx into the trachea and then into the lung, which is over at this specimen." "Here, we look at the left lung of a smoker, and the right side, in between the heart, the lung tissue has been dissected away and you look at the bronchi coming all from the trachea." "Our molecule of oxygen has travelled in the through the nose or mouth, down through the larynx, down the trachea, through bronchi and into the lungs themselves, and here you see the two lungs and the thorax." "We have the plastinated specimen of lungs." "If I put these in front of my chest about like this, these are probably about the size of my lungs, fully inflated." "Lung tissue, itself, is constructed rather like a sponge." "And the purpose of this sponge is to create a large surface area for the oxygen to dissolve in the blood." "Somebody worked out once that the combined surface area of both lungs is about the size of a tennis court." "I don't know how accurate that figure really is, but it is certainly large, that's the point a large surface area." "And this is a microscopical section of a normal lung." "These spaces are the air spaces, these are the blind-ending sacks were the air is sucked into the lung, down the bronchi and then into these sacks, which are the final part of the lung tissue and are called the alveoli." "And these are the little blood vessels, through which blood circulates in the lung and you can see they are brought into very, very close contact with the air spaces so that the oxygen can dissolve in the blood." "Things can can, of course, go wrong with the lungs." "Here is a pair of lungs from a smoker." "Smoking is a pretty bad thing to do for lungs really, because it has got lots of chemicals and tar in it." "And you can see that these lungs are a lot darker than the previous pair of lungs, because this material gets deposited in the lungs and it doesn't go away with time." "And this material can do damage to the lungs by causing inflammation." "And one of the results of this inflammation can be the condition known as emphysema which is illustrated in the next microscopic slide." "And you can see by comparison with the previous slide, which was at the same magnification there is a lot more space here and a lot less boundary." "And the results of that is that there is less surface area for the oxygen to be dissolved in the blood which is why people with emphysema have difficulty breathing, have difficulty getting oxygen into their blood." "If we return to the sponge analogy emphysema is a bit like a sponge with big holes in it." "And these big holes are caused by the destruction of the normal small dividers between the air spaces." "One of the most undesirable consequences of long-term smoking is CANCER of the lung." "And that is illustrated in the next picture where you see these islands of cancerous tissue have moved through and completely destroyed the lung tissue." "One final point I would like to make, just returning to his plastinate, is another condition that people have heard of is asthma." "What is asthma?" "Asthma is another condition where it is difficult to get air in and out of the lungs." "And in this case, it is because the muscles in these small bronchi constrict and make the bronchi narrower." "That makes it more difficult to pull air in and out of the lungs and thereby makes an asthma sufferer feel they have to breathe harder to actually get the air in and out of their lungs." "Were we have put our molecule of oxygen into the lungs, but let's now actually show you what the lungs look like when they inflate." "This is a very special event." "I actually bring to life the dead lung of this gentleman." "To accomplish this, I have first to find the trachea and the trachea is just here, below the larynx." "And here I take the trachea out with its... the trachea, here with its cartilages, and I cut..." "I cut the trachea so now, between two cartilages, between two of the rings of the cartilages." "So here, actually, the opening of the cut..." "So everything should look neatly." "And now it's about the time to put the tube in to the trachea and to inflate this man's lung." "Okay, please." "Come, come, full, full...." "There you see the lungs inflating." "And this is the process that happens every time you breathe in and the deflation is what happens every time you breathe out." "The lung is airtight, so the lungs are blind-ending sacks, in which the air goes and comes out again." "And if the lung gets a hole in it, that's a problem because that breaks the seal between the lung and the chest wall." "And if that happens, it is called a pneumothorax the lung will then actually collapse and not be inflatable by the muscles of the thorax." "And the pneumothorax is a type of medical emergency which has to be relieved by putting a drain into the pleural cavity, to get rid of the air and by ensuring that the hole in the lung is sealed up." "So we do it another, another onetime." "So that is expiration with the lungs going down." "Perhaps if you could put some more air in again." "That is inspiration, with the lungs going up." "Breathing in, breathing out." "So, our molecule of oxygen has entered the lungs, into the air sacks and been able to dissolve in those small blood vessels around the outside of the air sacks." "And in order to be able to describe and show you the next stage of its journey, we are now going to remove the lungs." "And I have to be very careful, because those cut ribs are very dangerous and I easily can hurt myself." "Say for I take as protection a little paper around those cut rib ends." "And now I am ready to go inside and actually take the left lung out." "And" "what I have to cut is a little connection between the pericardium of the heart the heart sack,and the lung..." "So it is only connective tissue." "And now, actually, the so-called root of the lung is on my right middle finger." "The lung, actually, has this one connection with the central structures." "It is organised a bit like a hand in a bag and my wrist is where the connection of the lung, here, is called the lung hilum and that's now going to be cut through, which will allow the lung to be removed from the chest." "So, I do this with the right lung as well." "It is more difficult because there are some adhesions, they must have been inflammation and the inflammation actually resided in a kind of connection between the lung and the rib cage." "Adhesions are the result of inflammation and they result by inflammation sticking two surfaces together that normally rub over oneanother." "In this case here in the lung that condition is known as pleurisy." "So, the condition of pleurisy is inflammation of the pleural lining, causing the lung to stick to the outside wall of the rib cage and that is what is known as an adhesion." "You can also probably see that the colour of this lung is a lot darker than the colour of this lung." "That is because this person died with fluid on the lobe that is being held up, there." "So over here, at the tongue of the lung, it is called, here, the lower part," "I have to cut this adhesion between the lung and the middle part over here." "The fat tissue around the heart is situated..." "So these adhesions make it slightly more difficult to remove the lung on the right side than would normally be the case and they are just being loosened-up, prior to cutting through the lung at the hilum." "So I take now the right lung out." "I reflected, you see, very clearly the 1,2,3 lobes upper, middle and lower lobe." "And from this side, I will cut now the veins running to the heart and the trachea." "So, there already I open connections between the heart and the lung lung veins." "The first lung vein here and I continue and here, I open the trachea, the right bronchus." "Another vein..." "So, this is typical for the blood vessels between the heart and the lung." "They are very clearly to see, here." "And I cut it, so" "And a tray, please." "Here is the right lung, with the adhesions of this gentleman, thank you." "And I do the same on the other side." "Again, I reflecting the lung and you see only two lobes, one lobe,upper lobe, lower lobe, which is worth just explaining that the right lung normally has three lobes, while the left lung only has two lobes" "and, in fact, the upper lobe of the left lung has a little extension, which is equivalent to the middle lobe of the right lung." "So, and now we have the left lung." "Just now to show you these lungs which I have just taken out." "Well, we have now shown you the function of the lungs,the bellows which allows us to pull the oxygen into the body and we have shown you how it is able to dissolve in the blood." "So the next part of this evening's demonstration will be to show you how it is circulated around the body by the world's most reliable pump, the heart." "In fact, the heart is in two pumps one to pump blood around the lungs and another to pump blood around the body." "Now, this is actually quite a difficult system to understand." "Although the general anatomy was known to the ancient Greeks, the precise continuity of the connections was not worked out until as late as 1628, when an Englishman named William Harvey published a book called 'On the Movement of the Heart and Blood in Man and Animals'" "a book which actually marks the beginning of modern scientific medicine." "So, before we actually show you the heart itself, let's actually show you what the heart has to do." "Let's show you the extent of the tubing that the heart has to pump blood around." "Those specimens are blood vessel configurations." "How I achieved them?" "The body was injected by polymer." "After curing the polymer, all the normal tissue was taken away by enzymes, by water and what we see here - the blood vessels of the heart." "From the heart, the blood goes to the head and you see here, very nicely, injected the brain." "To both sides of the body, we go to the arms" "But you see even here, the thoracic shield is nicely injected." "So, blood goes everywhere, even into the bones, here, all arteries down to the lower extremities." "What's very clear in these really very beautiful specimens is the large arteries, through which the blood is mainly distributed." "But the really striking thing is the way our arterial system and our blood system goes everywhere throughout the body." "Every single little cell in your body needs to have access to oxygen to keep its life-fires burning." "And you can see here, these blood vessels virtually outline our entire bodies." "You can see, here, the dense blood-vessel beds of the fingertips." "You can see here the lips and the nose and the ears." "And you can see underneath this bed of vessels in the scalp, the very dense vascular bed of the brain." "And I like to show you now how the blood actually moves in this gentleman." "As we experimented it with the lung, we will do the same with the vessel." "I need my gloves and we will show you how the blood actually moves into the intestinal tract." "And for that, I need some artificial blood." "We have prepared for that and up there there is a artificial blood." "Would you come down, please and my assistants, thank you much, brings in, Nadine, the ladder." "And we like, now, to inject" "the abdominal vessels of the abdomen and we see how the blood, artificial blood, here - it is polymer, red - a kind of flexible silicone, enters all the small veins of the intestinal tract." "I will open, now, the tap and give way for the artificial blood." "And at first we see here, the vessels around the stomach to fill up." "So, what we are seeing here is the filling-up of a vascular bed." "This is what the heart puts its energy into with every beat pushing the blood around the vascular system, in this case, the vascular bed of the intestine." "And this is what the function of the heart is to transfer its energy into pushing the blood around the circulatory system." "Every vascular bed has to be filled and in this case we seeing the vascular bed of the gut being filled by the polymer." "Okay, so what I like to demonstrate is here the surface of the stomach now is very small vessels coming from both sides and filling even the space in between." "You see here, the large interest, nicely injected as well." "And here, the small intestine." "What is always very impressive about this sort of demonstration is that when you place a flow through a vessel, how it reaches every last corner of the vascular bed that that vessel is responsible for supplying." "The next what I want to do is to remove the organs and then to slice open the heart." "Now I am ready to open the heart." "To be able to do that, I have to open the pericardium." "And the pericardium is just this sack around the heart, covered with a lot of fat, in this case." "So the heart is the world's most reliable pump." "In a long human lifetime, it may beat two or three billion times and the pericardium is the sack within which the heart sits and which stops it sticking to, or getting tangled up in, anything else within the thorax." "In a moment I will take the heart and it looks very wonderful, so be prepared." "And now, I open the pericardium and we look at the heart, with a lot of fat covered." "And in the natural position, here, resting in the diaphragm, it is laying like that." "Up here, we see the aorta." "I take now the knife,large knife, Gunter, large knife." "A long knife it is better cut, zhunnng" "And now I will cut open the heart, just parallel to its diaphragm." "And there it is." "I see here, the right chamber, here the left chamber, the valves." "And in the middle there is the septum if you could indicate the septum." "Here's the septum." "This is the large bit of heart muscle that is part of the left ventricle that separates the thick left ventricle from the thinner right ventricle and it is through this septum that the condition of 'hole in the heart'" "is sometimes found congenitally when the left and right ventricles can communicate with each other." "In order, now, to show you better the incoming and outcoming vessels, especially the veins,I take here a heart, fixed, resting, projected on my own body on the diaphragm." "And when I turn it around, then you see, here, the vessels, this is the lower vena cava." "Actually, the old blood, which has no oxygen any more goes up into the vena cava." "From the top of the body, from the head, from the upper arms, there is coming from the lower vena cava, the blood as well." "So, and from here, it runs out of the right heart to the lung and then it comes back from the lung, it is oxygenated and it goes just right in here, into the left atrium," "which is actually at the back of the heart." "This is called the so-called 'Venous cross' of the heart." "The blood from the lower part of the body enters here through the inferior vena cava, comes from the upper extremities and from the head, through the upper vena cava, goes out through the right heart, right into the lung" "and comes back from the lung, oxygenated, just from the right side and from the left side." "Marius could you show this, so actually behind me it would look like that." "From the lung, from the body and then going out here to the lung and here the aorta, to the head,all those of vessels to the head." "Here, here and here and at the back, the large aorta,nurturing the lower part of the body." "This plastinated heart just shows the same view that we had seen in the bisected heart in the body." "And you can see, here, a thin right ventricle." "This is the ventricle that is responsible for pumping the blood to the lungs." "And we see a thick left ventricle and this has to be much thicker because this side has to pump the blood all the way round the body." "So, everybody knows what the heart is and roughly where it is, but it is a surprisingly difficult organ to understand, so let's just recap the flow of blood through the heart." "It's got two pumps the right side and the left side." "The right side takes the deoxygenated blood from the body and pumps it out through the pulmonary artery into the lungs." "The return from the lungs happens on the back of the heart." "The pulmonary veins bring oxygenated bloods from the lungs into the left atrium." "That then passes into the large chamber of the heart,the left ventricle which pumps the blood out through the main artery of the body,the aorta, up, round and down to all the vascular beds of the body." "And, thank you," "I can show you this with, perhaps, greater clarity on the plasma screen over here, where we have an image of an injected arterial system of the whole body." "And here you can see the aorta, coming up from the heart, curving round the back, moving down the body." "It splits round-about the area of your umbilicus, or tummy-button, which is higher than people often imagine that is." "And the main arteries come down to the legs here." "The arteries supplying the kidneys come off here and the arteries to the arms and the brain and the head go off at the top, there." "And we will now try to show you some of these major branches in our dissection specimen." "To show you the main arteries, now, within the body after removing the organs," "I want to show you here again, the left ventricle and here the aorta starts and let's go round, the aorta goes over here, it goes up and goes here, down." "It goes down all the way over the aorta, nurturing to this side, on the left side, the kidneys going down here and branching to the left and to the right." "It is called iliac artery." "Nurturing the leg, here, on the left side, here on the right side and all the nurturing the small pelvis with the genital organs." "One of the arterial branches that you can't see on the main specimen, there, that I'd just like to just demonstrate to you on this plastinate of an opened heart, is what feeds the heart itself." "The heart being part of the body also has to be nourished and in fact, the first branches of the aorta and if you can see on that plastinated heart here, here is the left ventricle and here is the valve," "the aortic valve that stops the blood falling back into the left ventricle." "And there is a little hole, just there, above that valve cast, there are actually two of these, but only one of them is visible." "This is the exit for the coronary artery." "Through that hole, all the blood that nourishes the heart has to pass." "And if one or other coronary arteries gets blocked off, that can cause a dysfunction of the heart, that will manifest itself as a heart attack." "It is also worth saying that these arteries these large arteries that we have been demonstrating to you, have very elastic walls." "So, every time the heart contracts, the artery expands and then goes down again, expands and then goes down again." "And when you feel that expansion, for example at your wrist, that is what we know as the pulse." "And this is now the time to invite you for questions, please." "Once the heart stops beating, does all the blood in the body pool and settle and that's why we didn't see any blood when Gunther made the original cut?" "Well, when death occurs, the blood tends to settle by gravity inside the body, so it partly depends on the position the body is in when death occurs, but often people are lying down, in which case the blood tends to gravitate to the back of the body." "And that can minimise the amount of blood you see on dissection depending on what sort of dissection you are doing, yes." "The blood actually clots after death and this prevents that too much blood flows out when we open, especially the arteries." "'Artery' translated literally means 'without blood'." "This name was given by the old, first anatomists when they looked into the body and they really found no blood in the arteries, all the blood in the vein." "So when I primarily today cut arteries, there was no blood to be expected." "More questions?" "We saw how the lungs are blackened as a consequence of smoking." "Can your lungs recover if you stop smoking?" "When you smoke...not for five years." "Then the risk of getting cancer is nearly reduced to normal, provided that you were not a heavy smoker over more than 10 years." "In addition to the force of the heart and the diameter of the arteries, is there anything else that contributes to blood pressure?" "Well, blood has to have a pressure to be able to move forward." "And the factors that contribute to blood pressure are the force that is pushing the blood forward from the heart and the resistance that that meets in the arteries it has to go through." "So, blood pressure does very naturally a lot if you are lying in bed asleep, your blood pressure tends to be quite low." "If you are having a game of squash, for example, the heart is pumping out a lot more blood." "In life, the blood pressure is very variable and when a doctor talks about your blood pressure, what they are really meaning is your blood pressure at rest." "That has a normal range," "And a raised blood pressure is actually bad for your arteries, because that actually increases the energy transferred to the inside of your arteries, which can increase the risk of other diseases, like hardening of the arteries." "Next question, on this side, please?" "Yes." "Could you please describe hardening of the arteries." "Yes, hardening of the arteries." "Well, we can eventually demonstrate it on a plastinate, here." "This is any normal section of an aorta and you can see that this has a smooth internal lining." "Conversely, this is an opened aorta, which you can see has a very irregular internal lining." "Hardening of the arteries or atherosclerosis results from a low grade inflammation of the inside of the arteries and with time, that can become ulcerated and can also calcify." "And that is what 'hardening of the arteries' means." "The danger with hardening of the arteries is that it can weaken the arterial wall and that can lead to other problems, for example, aneurysm, which is any dilatation of an artery like the aorta, mainly due to atherosclerosis or hardening of the arteries." "Because the microphone is just over there, please." "Why do you think this man died?" "The reason for death of this man had nothing to do with what we showed today with the blood vessels, circulation." "But when I go over here to the liver, then you see that his liver is quite bumpy it has a quite coarse surface." "This actually, this is actually a liver cirrhosis." "You know?" "Diseases surface." "In a normal liver this will be absolutely fine and smooth." "The cause of liver cirrhosis has many reasons alcoholism, chronic alcoholism is the major reason." "This is actually blocks the blood flow to the heart, because of the metabolic problems, like more urea in the blood, makes brain trouble and finally, the man may have died from that." "The veins in the oesophagus very often are distended, say may rupture they may give cause to fatal bleeding." "Let's just recap the journey of our oxygen molecule by coming back over to Juliet and Lindy, here." "And Juliet has drawn the respiratory and circulatory systems on Lindy." "So we can now follow the journey of our oxygen molecule." "I have got two laser pointers here a red for oxygen and a green one for burnt oxygen or carbon dioxide." "So, we started when our oxygen molecule came down the trachea and into the lung, where it mixed with blood in the air spaces of the lung and returned along the pulmonary veins into the left atrium and left ventricle." "It was then pumped out through the aorta and down to the furthest reaches of Lindy's body, in this case, right down to her toe, where it allowed her to wiggle her toe muscles." "It was there burnt and changed into a molecule of carbon dioxide, where it returned in the venous circulation, passing up the inferior vena cave, to the right side of the heart and then out in the pulmonary artery," "to be mixed again with the air spaces of the lung, where it diffused out and was breathed out through the trachea and into the outside world." "Thus, completing our journey."