Pco2 *20times = 0.6, 2.4, so the co2 carried in the arterial blood in dissolved form is more than the o2 because of its solubility.

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1 Physiology, sheet #9 Oxygen, is first dissolved in the plasma and the cytosol of the rbc, we have around blood constitutes 7% of our body weight, oxygen, in the capillaries is present in the rbc s and plasma, first it diffuses to the plasma because of the partial pressure difference, partial pressure means, each gas in a mixture of gases behaves as if it is the only gas available in this mixture, which means diffusion of o2 is not affected by co2 or other gases, not like sodium for example when it enters the cell because of the electro chemical interactions. It diffuses first to the plasma ( po2 100), but oxygen has high solubility in the plasma, and you can still diffuse more oxygen because when it is attracted it s partial pressure does not build up, so when the gas is soluble, it has a higher chance of diffusion. but the oxygen solubility is not high. Diffusion capacity for oxygen is, and for co2 it s And this means, in a pulmonary disease, most probably the arterial oxygen is going to be affected first, the patient comes with low po2 arterial, normal pco2 arterial because the co2 diffusion capacity is 20 times more is higher, but if you find po2 low and pco2 high, then that means there s too much damage, we re talking about an advanced stage, so normally in lung diseases both gases are affected but oxygen is affected first, oxygen can be reported as po2 arterial 100 this means nothing by itself, you must have additional information. Co2 Is fat soluble so it diffuses 20 times faster, co2 is more soluble in water so when it diffuses it is attracted by water, so you get more chance, both of them diffuse through the biological membrane easily,

2 the point is, what occurs later on, co2 partial pressure does not build up easily, you can add co2 to water without building partial pressure, because it is more soluble, but when the water becomes saturated then partial pressure starts to build up therefore oxygen solubility in plasma is negligible it is equal 0.003, so 0.03 * 100= 0.3 blood, the total oxygen con in a solution depends on its partial pressure and it s solubility, for co2 for example, co2 arterial, con. In dissolved form (co2 has 3 forms ) Pco2 *20times = 0.6, 2.4, so the co2 carried in the arterial blood in dissolved form is more than the o2 because of its solubility. O2 is dissolved form in negligible, oxygen consumption is equal to 200 deciliter per minute And this might rise up to 4 to 5 liters per minute (maximum oxygen consumption) during exercise. The heart ejects 5 liters per minute,= 50 deciliter, each deciliter of arterial blood it contains 20 ml of 0xygen (arterial), venous = 15. So the cells extracted 5 ml, so 5*20=25, you have 50 deciliter, from each deciliter you take 5, and that s how oxygen consumption equals 250 ml per minute. The dissolved form, we have 0.3, what our cells need is 5, so the dissolved form can only provide 6%, however if you allow the person to breathe pure oxygen, po2 will be over 600, 600*0.003=1.8, which is also not enough, we need 5! We need something else to carry o2, hemoglobin, number of rbc s is 5 million per micro liter. in each cell there is 280 million hemoglobin molecule. Hemoglobin A, ALPHA 2 BETA 2

3 HEMOGLOBIN F, ALPHA 2, GAMMA 2 HEMOGLOBIN S, ALPHA 2, BETA 2 (BUT IN THE BETA CHAIN, IN THE SECOND CHAIN, VALINE INSTEAD OF GULTAMIC ACID ) is the weight of hemoglobin, More than 70000, means that it does not filter through the glomelular capillaries, but hemoglobin will not be lost because it is inside the rbc. Hemoglobin has two states ferrous which can bind oxygen and ferric state which cannot bind oxygen, there is a reeducates in the red blood cell that converts the ferric to ferrous. advantages of having the hemoglobin in the rbc. 1 ) it is not filtrated in the kidney because it is present inside the cell, otherwise you will start urinating hemoglobin (hemoglobinurea) 2) there is a reductase in the blood cells to convert ferric to ferrous. 3) hemoglobin is protected from prtoteolytic enzymes in the plasma 4) it decreases viscosity. when viscosity is increased vascular resistance also increase so hemoglobin decreases viscosity. Hemoglobin is an allosteric protein and it can bind 4 molecules of oxygen. Oxygen must available to bind hemoglobin, and it s available in the cytosol, and the cytosol comes from the plasma, so we report the plasma po2, the more the po2 the more the binding but this isn t true, It is directly proportional but not linear, it s very difficult to bind at first ( phase one),

4 Rbc s doesn t have mitochondria so they are forced to burn glucose (glycolysis) and 2,3 diphosphoglycerate, is formed but we have mutase in the rbcs which converts the 1,3 to 2,3 which can bind to hemoglobin, 2,3dpg makes it difficult for oxygen to bind. Hemoglobin dissociation cure When it is 100% saturated assuming it s con. Is 20 then the oxygen con. Will be around (dissolved) = 20, but it also can be 100% saturated when the hemoglobin con. Is for example 7.5 and oxygen con. 10, so in anemic patients, po2 is normal or above normal, po2 alone and saturation alone are not enough. Oxygen is carried in three forms, 1) Partial pressure 2) Concentration, arterial =20, venous=15 3) Saturation. Hemoglobin, before it binds oxygen, we call it deoxy hemoglobin or reduced hemoglobin or meth hemoglobin, when it binds it becomes oxyhemoglobin, when it binds to co it becomes carboxyhemoglobin, and when it binds co2 it becomes carbamino hemoglobin, Remember : in one rbc there are 280 million hemoglobin molecule. The relation between oxygen and hemoglobin is sigmoidal, If you increase po2 arterial after saturation, the oxygen carried by hemoglobin will not increase.

5 When po2 is 60 the saturation is 90% which means decreasing, which means ascending to high altitude up to a point where, the arterial po2 is 60 and above your oxygen carrying capacity has not changed significantly, instead of having 20 ml you have 18 ml, and you need 5, so you are in a good shape so we have plenty of oxygen. When po2 is 40 (venous), at venous po2 75% is saturated because we have 15 ml. If the cell is very active, 25 % is not enough so it might extract 100%, the lowest partial pressure in the cell is in mitochondria, so the cell produces co2 and it binds to the hemoglobin forcing the hemoglobin to lose its oxygen, so affinity decreases when co2 binds, Right shifting of the oxygen hemoglobin curve means that at any po2 the amount of oxygen carried is less, and this occurs in four conditions, 1) When hemoglobin binds co2. 2) Increased 2,3 dpg 3) Decreased ph 4) High temperature. During exercise, blood flow to the brain 750 ml at rest, and during exercise the percentage is decreased not the volume. in the coronaries, at rest 250 ml at rest, and during exercise it increases to 750 ml, GI tract at rest, 1400 ml and during exercise it gets 600 ml, kidney at rest 1200 ml and during exercise 600, skeletal muscles

6 1100 during rest and during exercise, most of the blood goes to the blood, where can we get more oxygen? Two ways, either you increase blood and it can be increased 6 time (maximum) or you can increase Extraction ration, so if you increase extraction ratio by three times, 6*3 =18. Co is colourless and odorless and it binds hemoglobin 200 times stronger, and shifts the oxygen hemoglobin to the left, if air contains pco 0.4 milliliter mercury, and po2 arterial is 100, then 50% of hemoglobin is bind to oxygen and the 50% is bind to co, so if pco is 0.8 then hemoglobin will be saturated with co. co binds to hemoglobin it binds very strongly and it is difficult to extract, the problem is that when po2 arterial is100, the system doesn t hyperventilate to wash out the co and to add more oxygen. the only way to treat the co poisoning is by giving the patient pure oxygen and co2 will help stimulate ventilation. Hemoglobin f, has lower affinity for oxygen, but because it doesn t bind 2,3 dpg it has more affinity than hemoglobin A, the placenta is a membrane where the baby s blood mixes with the mother s blood it acts like a lung, po2 in interstitial space of placenta is 40. I couldn t understand this part so please refer to the record or the book. Ayman Noman

HCO - 3 H 2 CO 3 CO 2 + H H H + Breathing rate is regulated by blood ph and C02. CO2 and Bicarbonate act as a ph Buffer in the blood

HCO - 3 H 2 CO 3 CO 2 + H H H + Breathing rate is regulated by blood ph and C02. CO2 and Bicarbonate act as a ph Buffer in the blood Breathing rate is regulated by blood ph and C02 breathing reduces plasma [CO2]; plasma [CO2] increases breathing. When C02 levels are high, breating rate increases to blow off C02 In low C02 conditions,