1. Transport of Oxygen and Carbon Dioxide in Blood and Tissue Fluids

3. Gas exchanges in the alveoli
Driven by diffusion

4. Transport of oxygen and carbon dioxide in blood and tissue fluids
Oxygen diffuses from the alveoli into the pulmonary capillary blood because the oxygen partial pressure (PO2) in the alveoli is greater than the PO2 in the pulmonary capillary blood.
In the other tissues of the body, a higher PO2 in the capillary blood than in the tissues causes oxygen to diffuse into the surrounding cells.

6. Conversely the intracellular (PCO2) rises to a high value (because of metabolism ), this increase in (PCO2 ) causes carbon dioxide to diffuse into the tissue capillaries.
Then blood flows to the lungs, the carbon dioxide diffuses out of the blood into the alveoli, because the PCO2 in the pulmonary capillary blood is greater than that in the alveoli.

7. Gas pressures in arteries and veins

9. External respiration

10. Internal respiration

11. The transport of oxygen and carbon dioxide by the blood depends on both:
-Diffusion
-The flow of blood

12. Diffusion of oxygen from the alveoli to the pulmonary capillary blood
-The PO2 in the alveolus averages 104 mm Hg.
-The PO2 of the venous blood entering the
pulmonary capillary 40 mm Hg (because a large amount of oxygen was removed from this blood as it passed through the peripheral tissues).

13. The initial pressure difference that causes oxygen to diffuse into the pulmonary capillary is (104 – 40)= 64 mm Hg.

15. Transport of oxygen in the arterial blood
About 98 % of the blood that enters the left atrium from the lungs has just passed through the alveolar capillaries and has become oxygenated up to a PO2 of about 104 mm Hg.
Another 2 % of the blood has passed from the aorta through the bronchial circulation, which supplies mainly the deep tissues of the lungs and is not exposed to lung air) called “shunt flow.(

16. Oxygen transport and uses
Hb is 100% saturated with O2 when the RBCs pass through the lungs  all Hb molecules are fully loaded with O2
200 ml O2 carried per liter  x 5 liters  1000 ml O2 carried/min
Tissues only use 250 ml O2 per minute  only 25% of O2 molecules are used
Thus venous blood should have a saturation rate of 75%
Anemia: decrease in oxygen-carrying
capacity of the blood

17. So the PO2 of the blood entering the left heart and pumped into the aorta fall to about 95 mm Hg because of this admixture.
When the arterial blood reaches the peripheral tissues, its PO2 in the capillaries is still 95 mm Hg.
The normal intracellular PO2 ranges from (5 mm Hg - 40 mm Hg) averaging 23 mm Hg.

18. Oxygen transport in the blood
O2 from the alveoli diffuse into the blood
Then O2 enters the RBC and binds to hemoglobin
3% of O2 is dissolved in plasma while 97% is bound to Hb  oxyHb
The binding is reversible
Hb + O2  HbO2
104mmHg

19. Factors affecting the PO2
Rate of Blood Flow on Interstitial Fluid
If blood flow ↑ ↑ the PO2 ↑ ↑
2- Rate of Tissue Metabolism on Interstitial Fluid
If the cells use more oxygen for metabolism than normally, this ↓↓ the interstitial fluid PO2.

20. In summary,
tissue PO2 is determined by a balance between
(1) the rate of oxygen transport to the tissues
in the blood and
(2) the rate at which the oxygen is used by the tissues.

21. In tissues
O2 moves from HbO2 to free O2 in the plasma, then into the tissues
This is passive transport  diffusion

22. Role of Hemoglobin in Oxygen Transport
Oxygen is transported in blood by 2 ways :
1-chemical combination with hemoglobin in the red blood cells (about 97 %).
2- in the dissolved state in the water of the plasma and blood cells(3%).

23. 97% 3%

24. The oxygen molecule combines loosely and reversibly with the heme portion of hemoglobin. When PO2 is high, as in the pulmonary capillaries, oxygen binds with the hemoglobin, but when PO2 is low, (in tissue capillaries) oxygen is released from the hemoglobin.

27. Complete the table by adding high or low to the blanks
Affinity of hemoglobin under different conditions
Region of body
Oxygen concentration
Carbon dioxide concentration
Affinity of hemoglobin for oxygen
Result
Gas exchange surface
Oxygen is attached
Respiring tissues
Oxygen is released
Complete the table by adding high or low to the blanks

28. The oxygen-hemoglobin dissociation curve
Blood leaving the lungs usually has a PO2 of about 95 mm Hg, the dissociation curve that the usual oxygen saturation of systemic arterial blood averages 97 %.
Normal venous blood returning from the peripheral tissues, the PO2 is about 40 mm Hg, and the saturation of hemoglobin averages 75 %.

29. (1) the steep slope of the dissociation curve
and (2) the increase in tissue blood flow caused by the decreased PO2 ; that is, a very small fall in PO2 causes large amounts of extra oxygen to be released from the hemoglobin. the hemoglobin in the blood automatically delivers oxygen to the tissues at a pressure that is held rather tightly between about 15 and 40 mm Hg.

30. % saturation of hemoglobin
PO2 (mmHg)
% saturation of hemoglobin 10
13.5 20
35.0 30
57.0 40
75.0 50
83.5 60
89.0 70
92.7 80
94.5 90
96.5
100
97.5
mm Hg is a measure of pressure = millimeters of mercury
Atmospheric pressure of air is 760mmHg oxygen makes up roughly 21% whish is 159mmHg
Q: Plot a graph of PO2 against the percentage saturation of hemoglobin. The curve obtained is called the oxygen hemoglobin dissociation curve. 30

31. Oxygen-Hemoglobin Dissociation Curve

34. Amount of oxygen that can combine with the hemoglobin of the blood
The blood of a normal person contains about
15 grams of hemoglobin in each 100 ml of blood,
each gram of hemoglobin can bind with a maximum of 1.34 ml of oxygen.
(15 x 1.34 = 20.1)
this means that 15 grams of hemoglobin in 100 ml of blood can combine with 20 ml of oxygen if the hemoglobin is 100 % saturated.

38. Factors affecting Oxygen-Hemoglobin Dissociation Curve

39. Factors affecting Oxygen-Hemoglobin Dissociation Curve
A number of factors can affecting the curve :
pH:when the blood becomes acidic, the pH ↓↓ from the normal value of , the oxygen-hemoglobin dissociation curve shifts to the right. Conversely, an ↑↑ in pH from the normal 7.4 to 7.6 shifts the curve a similar amount to the left.

40. 2. increased carbon dioxide concentration,
3. increased blood temperature,
4. increased (2,3-biphosphoglycerate (BPG).
2,3-biphosphoglycerate (BPG): Is a metabolically important phosphate compound present in the blood in different concentrations under different metabolic conditions.

41. The Bohr Effect.
The release of O2 from the blood in the tissues and enhancing oxygenation of the blood in the lungs after shifting of the oxygen-hemoglobin dissociation curve to the right in response to ↑↑in blood CO2 and H ions is called Bohr Effect.

42. As the blood passes through the tissues, carbon dioxide diffuses from the tissue cells into the blood. This increases the blood PO2, which in turn raises the blood H2CO3 (carbonic acid) and the hydrogen ion concentration.
These effects shift the oxygen-hemoglobin dissociation curve to the right forcing oxygen away from the hemoglobin delivering large amounts of oxygen to the tissues.

43. The opposite effects occur in the lungs, where CO2 diffuses from the blood into the alveoli. This reduces the blood PCO2 and decreases H ion concentration, shifting the oxygen-hemoglobin dissociation curve to the left and upward. Therefore, the quantity of O2that binds with the hemoglobin at any given alveolar PO2 becomes considerably increased, thus allowing greater O2 transport to the tissues.

45. Effect of BPG to Shift the Oxygen-Hemoglobin Dissociation Curve
In hypoxic conditions the quantity of BPG in the blood ↑↑ shifting the oxygen-hemoglobin dissociation curve to the right.
This causes oxygen to be released to the tissues Therefore, under some conditions, the BPG mechanism can be important for adaptation to hypoxia, especially to hypoxia caused by poor tissue blood flow.

46. Shift of the Dissociation Curve During Exercise
During exercise curve shifts to the right, thus delivering extra amounts of O2 to exercising muscle fibers.
why?
1-the exercising muscles, release large quantities of CO2;
2- other acids released by the muscles increase the H ion concentration in the muscle capillary blood.
3- the temperature of the muscle often rises 2° to 3°C, which can ↑↑ oxygen delivery to the muscle fibers.

48. In the lungs, the shift occurs in the opposite direction, allowing the pickup of extra amounts of oxygen from the alveoli

50. Altitude sickness
Caused by acute exposure to low partial pressure of oxygen at high altitude
Compensated by altitude acclimatisation – body combats it by producing more red blood cells.

51. Hemoglobin Loading and Unloading of Oxygen

52. Fetal hemoglobin affinity is higher than adult hemoglobin WHY?

54. Higher affinity haemoglobins
Fetal haemoglobin – has higher affinity than maternal Hb, so can obtain O2.
Myoglobin – red pigment in mammalian muscles. Has a higher affinity for O2 than Hb – only releasing it a very low pp.Myoglobin ‘STORES’ O2.
Fetal Hb is gradually replaced with adult Hb (Hb A) over the first year of postnatal life.

55. Effect of diffusion distance from the capillary to the cell on oxygen usage
If cells are located farther from the capillaries, the rate of oxygen diffusion to these cells can become low and intracellular PO2 falls below the critical level required to maintain maximal intracellular metabolism.

56. Effect of blood flow on metabolic use of oxygen
The total amount of oxygen available each minute for use in any given tissue is determined by:
the quantity of oxygen that can be transported to the tissue in each 100 ml of blood and
the rate of blood flow.

57. Transport of oxygen in the dissolved state
At the normal arterial PO2 of 95 mm Hg, about 0.29 (0.3)ml of oxygen is dissolved in every 100 ml of water in the blood

58. Dissolved Oxygen
Henry’s Law states that the amount of gas that dissolves is proportional to its partial pressure.
Dissolved Oxygen=.003 mls x Pao x 100=.3mls of dissolved O2

59. Total Oxygen Content
Total amount of O2 in 100 ml of blood = the dissolved O2 + the O2 bound to Hb
The total oxygen content of specific blood is calculated as follows:
Cao2: (Hb x 1.34 x Sao2) + (Pao2 x 0.003)
- Cvo2: (Hb x 1.34 x Svo2) + (Pvo2 x 0.003)

60. Uptake of oxygen by the pulmonary blood during exercise
During strenuous exercise, a person’s body may require as much as 20 times the normal amount of oxygen.
Because of increased cardiac output during exercise, the time that the blood remains in the pulmonary capillary may be reduced to less than one half normal yet ,blood still becomes almost saturated with oxygen by the time it leaves the pulmonary capillaries.
How?

61. The diffusing capacity for oxygen increases almost threefold during exercise.
During exercise, even with a shortened time of exposure in the capillaries, the blood can still become fully oxygenated.

62. Transport of oxygen during strenuous exercise
During heavy exercise, the muscle cells use oxygen at a rapid rate, and cause the muscle interstitial fluid PO2 to fall from the normal 40 mm Hg to as low as 15 mm Hg. At this low pressure, only 4.4 ml of oxygen remain bound with the hemoglobin in each 100 ml of blood.

63. during heavy exercise, extra amounts of oxygen (as much as 20 times normal) must be delivered from the hemoglobin to the tissues. this can be achieved with little further decrease in tissue PO2 because of:

64. During strenuous exercise, when hemoglobin release of oxygen to the tissues increases another threefold, the relative quantity of oxygen transported in the dissolved state falls
to as little as 1.5 %.

65. If a person breathes oxygen at very high alveolar PO2 levels, the amount transported in the dissolved state can become much greater,
a serious excess of oxygen occurs in the tissues, and “oxygen poisoning” ensues. This often leads
to brain convulsions and even death, in relation to the high-pressure breathing of oxygen among deep-sea divers.

66. Combination of hemoglobin with carbon monoxide
Carbon monoxide combines with hemoglobin at the same point on the hemoglobin molecule as does oxygen; it can therefore displace oxygen from the hemoglobin, thereby decreasing the oxygen carrying capacity of blood.
A patient severely poisoned with carbon monoxide
can be treated by administering pure oxygen, because oxygen at high alveolar pressure can displace carbon monoxide rapidly from its combination with hemoglobin.

67. Normal Blood gas values
Arterial blood
pH=
Pco2=35-45mmHg
Po2=80-100mmHg
HCO3-=22-28mEq/L
Venous Blood
pH=
42-48 mmHg
35-45 mmHg
24-30 mEq/L

68. Tissue Hypoxia
Tissue hypoxia means that the amount of oxygen available for cellular metabolism is inadequate.
There are four main types of hypoxia:
hypoxic hypoxia - circulatory hypoxia
anemic hypoxia - histotoxic hypoxia
Hypoxia leads to anaerobic mechanisms that eventually produces lactic acid and cause the blood pH to decrease.

69. Cyanosis
When hypoxemia is severe, signs of cyanosis may develop.
Cyanosis is the term used to describe the blue-gray or purplish discoloration seen on the mucous membranes, fingertips, and toes whenever the blood in these areas is hypoxemic.
The recognition of cyanosis depends on the acuity of the observer, on the lighting conditions, and skin pigmentation.

70. Polycythemia
When pulmonary disorders produce chronic hypoxemia, the hormone erythropoietin responds by stimulating the bone marrow to increase RBC production.
An increased level of RBC’s is called polycythemia.
The polycythemia that results from hypoxemia is an adaptive mechanism designed to increase the oxygen-carrying capacity of the blood.