 Hey everybody Dr. O here in this video we're going to talk about the movement of oxygen and carbon dioxide throughout your body throughout your tissues and then into and out of your lungs as well. So what you can see here we are actually we're at the lungs we have the respiratory membrane which is going to be a single layer of simple squamous epithelium that forms the alveolus a little bit of a fused basement membrane of connective tissue then a single layer of simple squamous epithelium that is the capillary so that's the respiratory membrane so what you see here this would be we're looking at the the blood that's coming from the pulmonary artery so it's gone out to the body it's used up its oxygen it's picked up carbon dioxide and then it's being pumped back to the lungs from the heart. So you see the arrows carbon dioxide is diffusing from your blood into the alveolive your lungs because there's more carbon dioxide in this dirty used blood than there is in your airways that's why you see carbon dioxide being shifted to the left oxygen is diffusing into your blood stream because there's more oxygen in your alveoli than there is in this blood that's returning from your from your heart. Now we could talk about the partial pressures and all that but I want you to get bogged down with individual numbers 40 millimeters of mercury here there whatever just remember that diffusion is going to cause things to move from where there's a high concentration to low so carbon dioxide is driven into your lungs because there was more of it in your blood than in your airways oxygen is driven into your blood because there was more oxygen in your airways in your respiratory system than there was in your blood and then we go to the tissues and the opposite happens now the blood is being pumped you know from your left ventricle through your aorta wherever it's going to go and now this oxygen rich arterial blood is going to drop off oxygen instead of picking it up because there's more oxygen in your blood than there is in the tissues so oxygen is going to be detached from your hemoglobin making your oxy hemoglobin is now going to be called deoxy hemoglobin but the oxygen's been detached and it's going to be driven into your tissues where it can power cellular respiration also known as internal respiration and then carbon dioxide is going to be picked up by your blood because there's more carbon dioxide as this metabolic waste product in your body fluids in your interstitial fluid than is in your blood so the opposite has occurred so at your airways oxygen is driven into your your blood and carbon dioxide is driven out at your body tissues wherever we're at here oxygen is being driven out of your blood to your tissues your cells and tissues and carbon dioxide is driven in so think about that let's just kind of try to follow like a molecule of oxygen so we're at the airways oxygen is picked up by the hemoglobin on one of these red blood cells and it's going to be taken back to your heart through the left atrium left ventricle your heart pumps again blood travels through your aorta and it's going to travel through your circulatory system till it reaches your big toe or wherever it's going now we're here it's going to drop that oxygen off and while it's there it's going to pick up a co2 and we'll talk about how co2 is transported in a moment then it's going to flow back through your venous system it's going to get back to the heart reach the right ventricle where it'll be pumped into your lungs again to drop off that co2 and pick up another molecule of oxygen and do it again and again and again all right but so just you know almost all your oxygen is going to be carried on carried on hemoglobin we covered that back in the blood chapter a tiny bit can be dissolved in your plasma but let's look more specifically at the three ways that carbon dioxide is carried back so about number one about 7% of the carbon dioxide will be dissolved right in plasma and carried back to your your heart and lungs so about about you know 70% is going to be dissolved it's going to become what's called carbonic acid so as you can see here carbon dioxide and water are going to form carbonic acid that's a huge deal because that basically means that carbon dioxide is a proxy for this weak acid carbonic acid which is why your respiratory system is critically involved in the maintenance of your body's pH if you see an acid based disturbance in the body the first place you would look is the respiratory system because if you have too much carbon dioxide that means there's going to be too much acid in your blood and your pH would drop potentially dangerously low if you have too little carbon dioxide like if you're hyperventilating then you would have too little acid in your blood and your pH would climb so hopefully you can see why it's very very important we'll come back to acid based disturbances labor the last 23% of carbon dioxide is carried on carbamino hemoglobin so we thought we know what hemoglobin is oxy hemoglobin is hemoglobin carrying oxygen deoxy hemoglobin is hemoglobin that's dropped off its oxygen of body tissues but then a lot you know a decent sized chunk of carbon dioxide will actually attach to a hemoglobin forming carbamino hemoglobin and that's going to be that's how hemoglobin can help carry carbon dioxide back to your heart and lungs so when you think hemoglobin you should primarily think oxygen that's its primary job but it's like while i'm here i may as well grab some carbon dioxide and carry it back to your lungs and that's what it does all right so those are the three ways that carbon dioxide is transported through your your circulatory system okay that is the relationship between external respiration breathing in and breathing out and internal respiration that's how oxygen gets from your atmosphere to your cells where it can generate ATP and that's how carbon dioxide is carried away i hope this helps have a wonderful day be blessed