Oxygen Transport in the Blood (Nursing)

00:02 So now let's talk about oxygen transport and let's really talk about how we are actually transporting these oxygen molecules in our blood.

00:12 This occurs in two ways.

00:14 First we have a little bit dissolved in our blood plasma, but most of our oxygen is actually going to be bound to iron on our hemoglobin molecules found in our red blood cells.

00:31 So each hemoglobin molecule is actually composed of four polypeptide chains.

00:37 And each of these chains contain an iron containing heme group and is the heme groups that are going to carry the oxygen so each hemoglobin molecule can carry four oxygen molecules.

00:53 When oxygen is loaded onto the hemoglobin we refer to it as oxyhemoglobin.

01:01 When the oxygen is released from the hemoglobin.

01:04 We refer to it as reduced hemoglobin or deoxyhemoglobin.

01:12 So the loading and the unloading of oxygen is going to be facilitated by changes in the shape of the hemoglobin molecule.

01:21 The oxygen binds and the hemoglobin changes shape thus increasing the affinity for oxygen.

01:28 However, when oxygen is released the hemoglobin is going to change shape and decrease the affinity for oxygen.

01:38 When we have a hemoglobin, we're all for heme groups are carrying oxygen we refer to that as fully saturated.

01:48 When all four heme groups are not carrying oxygen however, we refer to that hemoglobin as partially saturated.

01:58 So the rate of unloading and loading of oxygen is going to be regulated in order to ensure that we have adequate delivery of oxygen to our cells.

02:10 Multiple factors are going to influence this hemoglobin saturation the most important of that being the partial pressure of oxygen.

02:20 However, there are other factors that can also affect the saturation including temperature, the blood pH, the partial pressure of carbon dioxide, and also concentrations of a molecule known as bisphosphoglycerate or BPG which reduces the affinity of hemoglobin for our certain molecules.

02:43 So now let's look at how this works in different parts of the body.

02:47 So in arterial blood the partial pressure of oxygen is 100 and there is a about a 20 percent oxygen volume compared to the blood.

02:57 So 20 milliliters of oxygen per 100 milliliters of blood.

03:03 Are hemoglobin molecules are going to be 98 percent saturated.

03:09 Because of this 98 percent saturation, further increases in our partial pressure of oxygen will actually produce a minimal effect on oxygen binding because there's just nowhere for these oxygen molecules to go because it's already pretty much saturated.

03:28 In contrast, in our venous blood the partial pressure of oxygen is much lower at 40 millimeters of mercury and because of this it contains a lower volume of oxygen at 15%.

03:44 Even still, at this lower partial pressure our hemoglobin is still about 75 percent saturated.

03:52 We also have what's known as a venous reserve which are oxygen molecules that are going to remain in our venous blood.

04:00 So although we consider venous blood to be deoxygenated.

04:04 There is still a low level of oxygen found in that blood.

04:11 So if we look at the dissociation curves for this what we find is that at sea level, there's plenty of oxygen, and the partial pressure in the lungs is going to be about a hundred and the saturation is going to be about 98%.

04:29 This however changes when we move to higher altitudes.

04:33 And the reason why is because at higher altitudes, the partial pressure of oxygen is lower, and because of that when we breathe in that air the partial pressure of oxygen is less at about 80 instead of at a 100.

04:49 However, even though this partial pressure is lower, the hemoglobin is still about 95 percent saturated.

04:57 So this is why we can climb a mountain and still be able to breathe pretty adequately until we get two parts where the oxygen levels are too low.

05:08 So now let's compare resting tissue to metabolically active tissue.

05:14 So in our resting tissue, the partial pressure of oxygen is going to be about 40 millimeters of mercury or 75 percent saturated hemoglobin.

05:26 However, and are metabolically active tissue are partial pressure of oxygen is even lower.

05:33 The reason why it's lower is because we're actually using this oxygen in order to undergo these metabolic processes, so we're undergoing cellular respiration and we're soaking up all of that oxygen.

05:48 This is okay up until a point when we get to a partial pressure of about 20 our hemoglobin is only going to be about forty percent saturated.

05:59 And that is because we have released about 35% of our oxygen into the tissues for use.

06:06 And so we have a lot less oxygen occupying our hemoglobin molecules.

06:13 So other factors that can influence hemoglobin saturation include things like temperature, the concentration of H+ molecules, which affects pH, the partial pressure of carbon dioxide, and the bisphosphate glycerate molecule that modifies the structure of hemoglobin.

06:32 All of these factors can result in a decrease and hemoglobins affinity for oxygen.

06:40 These effects usually take place and are systemic capillaries, and these enhancements and our unloading of oxygen molecules causes a shift in our oxygen hemoglobin dissociation curves to the right.

06:58 A decrease in these factors.

07:00 However, would shift the curve to the left thus decreasing oxygen and unloading from our hemoglobin.

07:10 BPG our bisphosphoglycerate is produced by our red blood cells during the process of glycolysis.

07:18 The levels of BPG are going to rise when oxygen levels are low and when these levels rise, this is going to cause a lot more oxygen unloading.

07:32 As our cells metabolize glucose several things happen.

07:36 First when they're using oxygen.

07:39 This is going to increase the partial pressure of carbon dioxide as well the concentration of H+ molecules and our blood capillaries is also going to increase an increase in the H+ molecules leads to a decrease in our blood pH, or it makes our blood more acidic also known as acidosis.

08:04 This plus increasing the partial pressure of carbon dioxide is going to cause the hemoglobin oxygen bond to weaken and this is referred to as the Bohr effect and this is going to lead to oxygen unloading.

08:22 Another thing that happens as we metabolize glucose is heat production.

08:27 Heat production and our active tissues are going to directly as well as indirectly decrease our hemoglobins affinity for oxygen molecules, again, increasing the oxygen unloading from the hemoglobin.