In the first place we will analyze the antomophysiology of the breathing system and its relationship with the cardiovascular apparatus. We will exhaustively develop the concepts of diffusion (gaseous exchange) and blood oxygenation. We will also introduce the concept of pressure as well, including a briefing about the Dalton Law.
In the second place we will in the same way describe the anatomophysiology of the renal system. We will be interested in this case to develop notions of the hydro-saline equilibrium and to make a description of the renine –angiotensine –aldosterona system and its functionality.
Breathing System
Concept of Pressure and Dalton Law: Pressure is defined as strength on a surface. When we talk about atmospheric pressure we are dealing with a gaseous mass pressure on earth’s atmosphere. The atmosphere is a gaseous mixture composed by Oxygen (21%) and Nitrogen (78%). The 25 left is composed of other gases: Carbon Dioxide, Argon, and Neon. A very important data about the atmosphere is that its steam concentration varies. It will vary regarding its topographic location. In Buenos Aires we are next to the sea. An often heard complaint about our city is the following: “it’s humidity that’s unbearable”. Therefore, as water steam pressure varies, a change is produced in the gas composition. This is strictly related to Dalton Law which states that gases’ total pressure is equal to pressure 1 plus pressure 2 plus pressure 3, in other words, to the sum of the individual pressures. If pressure 1 is equal to oxygen pressure, pressure 2 is equal to Nitrogen pressure and pressure 3 is equal to water steam pressure. And if we find ourselves in Buenos Aires and the pressure 3 is the one that rises, the other will lower to maintain the total pressure in equilibrium (atmospheric pressure which is shared all around the globe). So this water steam pressure is variable. Within our body things are different. We will fit the internal media and this will determine a certain water steam value. In such a way we will maintain it homogeneous as we ourselves control the rest of the partial pressures and the water steam pressure itself, fact which does not take place outside ourselves, in the environment as a whole. So far we have said that barometric pressure is the air column pressure on the earth environment. We have to take into account that this will vary not only because of the water steam pressure. Altitude is also to be taken into account. When we climb a mountain, we bear fewer gases on top of us. Thus, pressure is lower, and also lower is the exercise of that pressure. Therefore, if I climb a mountain total pressure diminishes, and all partial pressures will also be lower. One of them is that of Oxygen. That is why when you climb a mountain, one of the problems you face is the lack of Oxygen. The organism will adapt itself, it will change, to meet that fewer availableness. When making any exercise and due to other reasons, oxygen availability also diminishes. Thus, physiological changes which any organism will experience in altitude and during exercise will be the same since in both cases need to adapt itself to smaller oxygen availability.
Some Data
At sea level, which is the value we have and the usual considered standard, barometric pressure equals 760 mmHg (remember that mmHg is a pressure unity). We had pointed out that 21% of that barometric pressure was Oxygen. Thus oxygen partial share of that pressure is 158. Nitrogen’s share, on the other hand, is 592.
An important element to consider is that if anything changes, the atmosphere does not alter its composition. The share (i.e. 21%) does not change. What might change is the absolute value, the pressure. In other words, 21% of that barometric pressure always will be made out of oxygen. If a climb a mountain what lowers is the total pressure, it could go down to, let us say, 500. But always, oxygen will have its 21% share of that.
Inside the organism things are similar, as long as there are no gas alterations. If any other gases were added, then the composition might vary. But if the only thing which is modified is pressure, then the composition remains the same. In heights the 21 % oxygen share will always remain the same, as we have seen. However, within any organism, what happens? Water steam pressure turns constant. Within the organism the water steam pressure is of 47 mmHg. This value is constant, thus percentages may change and this is due to the Dalton Law.
760 mmHg is also 1 atm (which is what the international standards have set). When you are listening to the radio you hear that the normal pressure is of 1013 Hectopascals. It is the same. In a Physiology book you are going to read 1 atm., but in experiments as the ones we will see in this oldclass we will work with mmHg. That is the barometric pressure. Reviewing: sea level barometric pressure equals 760 mmHg. If a person climbs a mountain then the total barometric pressure diminishes but its composition remains the same: 21% oxygen, 78% N. However, the amount of oxygen particles there is in that atmosphere is lower. Thus I reach a smaller amount of oxygen particles and of oxygen availability. And my body will have to adapt to that fact and I will hyper-ventilate, it will open its vessels; it will try to alter some things in order to take the maximum advantage of that oxygen. While making any exercise, and for other reasons, I will also have fewer oxygen availability, and that is why the changes that the body undergoes are similar. They are changes in the total barometric pressure with no alteration of the percentages. Composition does not change. What do change are the vales of the partial pressures.
Now, air gets in the organism and the last will set a water steam pressure value that might probably be different from the environment which surrounds us. Once these values alter, the others will follow, and so will occur with the percentages according to Dalton’s Law: the sum of the partial pressures equals total pressure.
Inside the organism water steam pressure is still: 47 mmHg. That is why in the organism we will refer to it as barometric pressure Z and the rest of the percentages we will take them from there. Pressure Z will be of 760 mmHg minus the figure that belongs to water steam pressure: 713 mmHg and out of this total we will calculate the other values.
Environment and our Organism
Which are the changes, the differences, between the body’s atmosphere pressure (alveolar atmosphere) and the environmental one (earth’s)? It’s great. Inside us steam water pressure remains constant, outside us is variable. Not only is constant. Its still value is of 47 mmHg. There is also another important difference. We had stated that the atmosphere composition was 21% Oxygen, 78% Nitrogen and the rest made out of Argon, Helio and Carbon Dioxide. Not inside the body. Inside the body Carbon Dioxide has a very important presence. We produce it. Our tissues will produce Carbon Dioxide in such a way that within the alveolus, in the capillary alveolar, we will find an important amount of it. Our body will release it towards the environment. So, difference number two is the great Carbon Dioxide concentration. Its presence is significant.
Gaseous Exchange
We have stated that our total pressure inside our body will be called barometric pressure Z. So, we will work from that total, that maximum figure. Starting from that point, calculated oxygen pressure will be of 149 mmHg and what we call oxygen cascade begins to take place. We know that we will be delivering oxygen to other structures, so that the oxygen inspired pressure is what we can find in the respiratory tracts. It reaches the alveolus in a weaker fashion. It also reaches the arterial blood. As it goes though the body, the oxygen arterial pressure will be lower. We shall remember that when we described the aorta’s key (cayado) we stated that its first branches will possess a higher oxygen arterial pressure and that they will reach the organs which need it the most, starting with the brain and the heart. The last vessels, (i.e. toes) will not reach the same arterial pressure. Thus, inspired oxygen pressure is in its highest point. Inside the alveolus is already somehow lower (100mmHg). When it reaches the blood the oxygen arterial pressure is of 90 mmHg. Once arteries branch themselves into arterioles, the pressure is obviously lower. Finally inside the capillary is even lower. The farther we are from the heart, the lower the oxygen pressure is. This is something we have to comprehend conceptually. Why is that so? It is so because from now on we will abstain to mention it. It is quite difficult to consider an oxygen variable pressure in blood. So from now on, we will set (according to the author) the oxygen arterial pressure in 90, 100. We should really comprehend that there really exists an oxygen cascade. That its concentration really lowers. And when it reaches the blood is really low but it will be oldstronger than Carbon Dioxide which was produced in our tissues.
Air will get in the body through the nose and the mouse, then will enter the respiratory tracts (pharynges and larynges). The larynges will divide into bronchia (left and right), these will branch into bronchioles. The bronchia have, in the beginning, a very solid, cartilaginous structure. Bronchioles, on the other, hand are absolutely malleable. The same way the vessels narrow their walls in order to allow the gaseous exchange to take place, something similar goes on with the bronchia, bronchioles.
However, they are not alone. They are inside a structure called lung. Lung will act as a protection. Thus, everything outside the lung is more solid, more cartilaginous. If we go the other way around, to the inside, everything will become softer and will be inside a soft mass which protects it. Besides the functional need (exchange) what is inside also get softer because it is protected within an also soft, solid mass.
Lungs possess lobules, three in the right one, two in the left. There is no difference functionally speaking. They are divided by caesuras but they are not completely apart.
The bronchiole, already weak, is surrounded by structures named alveolus. These are formed by alveolar cells or neumocytes. Neumo means air. If one wants to be even more schematic, along with this bronchiole branching we will find arteries and bronchiole veins. The lung functionality is destined to allow the exchange of air coming from the bronchia and blood which comes from the organism. Air comes from the bronchioles and blood from the lung capillaries (alveolar) which in turn come from the veins) and have a vein-capillary-artery structure. Before we had referred to another vein-capillary-artery, and it was leaving oxygen and taking Dioxide Carbon. At the lung level, instead, it comes carrying Carbon Dioxide, or a partial low oxygen pressure, reaches the capillary , the exchange is produced, the capillary delivers the Carbon Dioxide to the alveolus and receives oxygen and then an artery with arterial blood is formed which has a partial high oxygen pressure. This is gaseous exchange. Think about the importance the neumocite will acquire as a barrier against that gaseous exchange. Any affliction the neoumocite might have could be serious since it will not allow that exchange. Just think that the structure is the bronchia which contain air. At the alveolus level it possesses the neumocite which will form a gaseous exchange barrier and the blood at a capillary level which will come from a vein carrying Carbon Dioxide or a partial low oxygen pressure, and the artery with a partial high oxygen pressure. We are once again reviewing Dalton’s Law, here the Carbon Dioxide partial pressure is high and will condition the partial oxygen pressure to be low. Why? It is because the sum of the partial pressures will yield a constant total. A superior presence on one side provokes an inferior on the other. At any rate, within the body constant values are not to take into account, only relative values are important. Once one of them is higher, the other is lower, no matter what that figure might be. We will now offer the normal values. Inspired Oxygen Pressure equals Alveolar Oxygen pressure which equals arterial oxygen pressure equal to 90-100. Carbon Dioxide Arterial Pressure will be of 40 mmHg. In vein blood that figure could be higher.
Let us introduce one more concept. R equals breathing coefficient. It is the relationship between produced Carbon Dioxide and consumed oxygen, and if we want we might think of it as the performance of oxygen. This is so because the Carbon Dioxide energy which my body produced happened to be generated by oxygen. So R will depend upon our main source of energy: our food. We need it to keep our energy, to maintain our muscles and keep the same and constant internal rhythm. We need then oxygen and food. Thus, if our only food were carbohydrates, R equals 1, if it were proteins R equals 0.5 and in a mixed balance the equation is R equals 0.82. This will be mainly useful for the alveolar gaseous equation.
Oxygen will help to allow us to use our food as a source of energy.
Alveolar gas equation is a calculus to determine the alveolar oxygen pressure and comprehend the factors which will modify it. Alveolar oxygen pressure is equal to inspired oxygen pressure minus alveolar Carbon Dioxide pressure divided by a breathing quotient plus a small correction factor usually calculated in 2. According to this formula my inspired Oxygen pressure is 149 mmHg, my alveolar Carbon Dioxide pressure is 40 (there is no much difference with the alveolar pressure) divided by R (which we said it was 0.82 plus the correction) and this will result in 100 as Alveolar Oxygen Pressure. We have to comprehend too that in altitude, when atmospheric pressure diminishes, it also lowers the oxygen pressure figure which also means that my inspired pressure will lower and this will provoke an enormous alveolar pressure. That is why high surfaces influence the body since anything that might block respiratory tracts, will provoke a lower inspired oxygen pressure, a lower quantity of oxygen and therefore a smaller quantity of that substance inside the alveolus. My Carbon Dioxide alveolar pressure also rises when I hyper-ventilate. I favor the entering of a major quantity of CD within the alveolus and my oxygen alveolar pressure will also be affected. The respiratory quotient is moreover a conceptual principle. It is difficult to evaluate the respiratory quotient. It is important to comprehend the relationships. It is important to notice, for example, that a person’s alimentation influences his capacity to make good use of the oxygen.
Therefore, as water steam pressure varies, a change is produced in the gas composition. This is strictly related to Dalton Law which states that gases’ total pressure is equal to pressure 1 plus pressure 2 plus pressure 3, in other words, to the sum of the individual pressures. If pressure 1 is equal to oxygen pressure, pressure 2 is equal to Nitrogen pressure and pressure 3 is equal to water steam pressure. And if we find ourselves in Buenos Aires and the pressure 3 is the one that rises, the other will lower to maintain the total pressure in equilibrium (atmospheric pressure which is shared all around the globe). So this water steam pressure is variable. Within our body things are different. We will fit the internal media and this will determine a certain water steam value. In such a way we will maintain it homogeneous as we ourselves control the rest of the partial pressures and the water steam pressure itself, fact which does not take place outside ourselves, in the environment as a whole. So far we have said that barometric pressure is the air column pressure on the earth environment. We have to take into account that this will vary not only because of the water steam pressure. Altitude is also to be taken into account. When we climb a mountain, we bear fewer gases on top of us. Thus, pressure is lower, and also lower is the exercise of that pressure. Therefore, if I climb a mountain total pressure diminishes, and all partial pressures will also be lower. One of them is that of Oxygen. That is why when you climb a mountain, one of the problems you face is the lack of Oxygen. The organism will adapt itself, it will change, to meet that fewer availableness. When making any exercise and due to other reasons, oxygen availability also diminishes. Thus, physiological changes which any organism will experience in altitude and during exercise will be the same since in both cases need to adapt itself to smaller oxygen availability.
Carbon Dioxide to the alveolus and receives oxygen and then an artery with arterial blood is formed which has a partial high oxygen pressure. This is gaseous exchange. Think about the importance the neumocite will acquire as a barrier against that gaseous exchange. Any affliction the neoumocite might have could be serious since it will not allow that exchange. Just think that the structure is the bronchia which contain air. At the alveolus level it possesses the neumocite which will form a gaseous exchange barrier and the blood at a capillary level which will come from a vein carrying Carbon Dioxide or a partial low oxygen pressure, and the artery with a partial high oxygen pressure. We are once again reviewing Dalton’s Law, here the Carbon Dioxide partial pressure is high and will condition the partial oxygen pressure to be low. Why? It is because the sum of the partial pressures will yield a constant total. A superior presence on one side provokes an inferior on the other. At any rate, within the body constant values are not to take into account, only relative values are important. Once one of them is higher, the other is lower, no matter what that figure might be. We will now offer the normal values. Inspired Oxygen Pressure equals Alveolar Oxygen pressure which equals arterial oxygen pressure equal to 90-100. Carbon Dioxide Arterial Pressure will be of 40 mmHg. In vein blood that figure could be higher.
