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Transport of Oxygen and Carbon Dioxide (PowerPoint)

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Transport of Oxygen and Carbon Dioxide (PowerPoint) Powered By Docstoc
					Physiology Lecture 20




           Tanveer Raza MD MS
            razajju@yahoo.com
Tanveer Raza MD MS MBBS
        razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation
Curve




                    Tanveer Raza MD MS MBBS
                            razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation
Curve




                   Tanveer Raza MD MS MBBS
                           razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation
Curve
 Arterial end of tissue capillaries
 (PO2= 95 mm Hg, 97% saturated Hb)
                      19.4 ml/ 100 ml blood
 Venous end of tissue capillaires
 (PO2 =40 mm Hg, 75% saturated Hb)
                        - 14.4 ml/ 100ml blood

 O2 released from Hb, under normal conditions
                        = 5 ml/ 100 ml blood

                                 Tanveer Raza MD MS MBBS
                                         razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation
Curve
    During Strenuous Exercise, O2 released from
     Hb can be         = 15 ml/ 100 ml blood
                               (PO2 =15 mm Hg)




                               Tanveer Raza MD MS MBBS
                                       razajju2@yahoo.com
Utilization Coefficient
   Percentage of blood that gives up O2 as it
    passes through the tissue capillaries is called
    the utilization coefficient

   Normal value                     about 25%
                                     5 ml/ 100 ml blood
   During strenuous exercise        75 – 85%
                                     15 ml/ 100 ml blood
   In local tissue where
     – Extremely slow blood flow
     – Very high metabolic rate      100%

                                   Tanveer Raza MD MS MBBS
                                           razajju2@yahoo.com
“Tissue oxygen buffer" system
   Maintains Nearly Constant tissue PO2
    – Atmospheric O2 Concentration Changes
       Hb Buffer Effect maintains almost constant
        tissue PO2
    – Tissue demand
       Steep slope of the oxygen-hemoglobin
        dissociation curve
       Increased tissue blood flow

                               Tanveer Raza MD MS MBBS
                                       razajju2@yahoo.com
    “Tissue oxygen buffer" system
   Maintains Nearly Constant tissue PO2: Atmospheric O2
    Concentration Changes
    – In high altitude PO2 can fall half of normal. When
      alveolar PO2=60 mmHg, arterial Hb is still 89%
      saturated with O2. So, tissue PO2 changes little




                                      Tanveer Raza MD MS MBBS
                                              razajju2@yahoo.com
    “Tissue oxygen buffer" system
   Maintains Nearly Constant tissue PO2: Atmospheric O2
    Concentration Changes
    – In deep sea (compressed air), PO2 may rise 10 times.
      When alveolar PO2=500 mmHg, O2 saturation of Hb can
      never rise above 100%, (only 3% above normal level of
      97%). So, tissue PO2 changes little




                                    Tanveer Raza MD MS MBBS
                                            razajju2@yahoo.com
“Tissue oxygen buffer" system




                   Tanveer Raza MD MS MBBS
                           razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
Shift of Oxygen-Hemoglobin dissociation
 curve to the right




                         Tanveer Raza MD MS MBBS
                                 razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
Shift of Oxygen-Hemoglobin dissociation
  curve to the right
1.   Increase in H+
       Blood becomes acidic (decrease in pH)
2.   Increased CO2 concentration
3.   Increased blood temperature
4.   Increased BPG



                                    Tanveer Raza MD MS MBBS
                                            razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
Shift to the right
 The   Bohr Effect
 Increase in H+ (decreased pH) and Increased CO2
 concentration shifts the Curve to the right
    Enhances 02 release from tissues



Increased Delivery of
O2 to the Tissues by
enhancing release of O2
from blood

                                  Tanveer Raza MD MS MBBS
                                          razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
Shift to the right
 The Bohr Effect
   – As the blood passes through tissues
         Increased delivery of O2 to tissues


   – As the blood passes through lungs
         Opposite effect: Increased transport of
           O2 by blood


                               Tanveer Raza MD MS MBBS
                                       razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
Shift to the right
 The Bohr Effect
   – As the blood passes through tissues
            Increased CO2in blood
                – CO2diffuses from tissue cells into blood
            Increased H+
                – CO2+H20=H2CO3=HCO3+H+
               The curve shifts to the right causing
               decreased O2 combination with Hb and
               therefore delivering increased amounts of O2
               to tissues

   – As the blood passes through lungs   Tanveer Raza MD MS MBBS
                                                 razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
Shift to the right
 The   Bohr Effect
   – As the blood passes through tissues


   – As the blood passes through lungs
          Decreased CO2in blood
             – CO2diffuses from blood into alveoli
          Decreased H+
            The curve shifts to the left causing increased
            O2 combination with Hb, thus greater
            transport of O2

                                           Tanveer Raza MD MS MBBS
                                                   razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
Shift to the right
 Increased    BPG
   – BPG (2,3-biphosphoglycerate)
   – In hypoxia BPG in blood increases, thus shifting the
     curve to the right
             More O2 released in hypoxic condition




                                     Tanveer Raza MD MS MBBS
                                             razajju2@yahoo.com
Oxygen-Hemoglobin Dissociation Curve
During Exercise the curve shifts to the RIGHT
  – The Bohr Effect
  – Increased H+
           Exercising muscles, release large quantities
            of CO2 and several other acids, increase H+
            concentration in muscle capillary blood.
  – Increased temperature
           Muscle temperature often rises 2-3°C
  – Increased BPG


                                   Tanveer Raza MD MS MBBS
                                           razajju2@yahoo.com
Metabolic Use of Oxygen by the Cells
   Metabolic use of O2 is controlled by
    – Rate at which ADP is formed
    – Diffusion distance from capillary to Cell
       Usually pathological
    – Blood Flow




                                 Tanveer Raza MD MS MBBS
                                         razajju2@yahoo.com
Transport of O2 in Dissolved State
   3% of total of O2 transported in dissolved state
     – During strenuous exercise, transport in dissolved
       state falls to as little as 1.5%

   Oxygen poisoning
    – If person breathes O2 at very high PO2, amount
      transported in the dissolved state can become much
      greater, sometimes so serious causing brain
      convulsions and even death
    – Example: high-pressure breathing of oxygen among
      deep-sea divers


                                     Tanveer Raza MD MS MBBS
                                             razajju2@yahoo.com
Carbon Monoxide poisoning
    CO combines with Hb (HbCO) at the same
     point as O2
      – Decreased O2 carrying capacity of blood
         Displaces O2 from Hb
         CO binds about 250 times more than O2

     – Less O2 released from blood
         Binding of CO at one of the 4 binding sites of
          Hb for O2 causes shift of dissociation curve to
          the left
            – Less oxygen released


                                     Tanveer Raza MD MS MBBS
                                             razajju2@yahoo.com
CO2 transport
CO2 transport
   Transported in greater quantities than O2

   Amount in blood depends on acid-base
    balance of body fluids

   In normal conditions amount transported from
    tissues to lungs is
                        = 4ml/ 100ml of blood

                                Tanveer Raza MD MS MBBS
                                        razajju2@yahoo.com
CO2 transport




                Tanveer Raza MD MS MBBS
                        razajju2@yahoo.com
Forms in which CO2 is transported

                           -
1.   In the form of HCO3
     • About 70%

2.   Dissolved state
     • About 7%

3.   Combination with Hb and Plasma
     Proteins
     • About 20%
                               Tanveer Raza MD MS MBBS
                                       razajju2@yahoo.com
Forms in which CO2 is transported
                          -
In the form of        HCO3
   Dissolved CO2 reacts with H2O to form H2CO3
    – Catalyzed by carbonic anhydrase inside RBC’s
                               +              -
   H2CO3 dissociates into H and HCO3
   Most of the H+ combine with Hb (powerful
    acid-base buffer)




                                   Tanveer Raza MD MS MBBS
                                           razajju2@yahoo.com
Forms in which CO2 is transported
                           -
In the form of         HCO3
   CHLORIDE SHIFT
    – Many HCO3- diffuse from RBC into plasma in
      exchange for Cl-, due to bicarbonate-chloride
      carrier protein in RBC membrane
    – Thus, Cl- content of
             Venous RBC’s > Arterial RBC




                                    Tanveer Raza MD MS MBBS
                                            razajju2@yahoo.com
Forms in which CO2 is transported

In Dissolved State

   Quantity of CO2 normally transported in
    dissolved state is about
                      = 7% of total
                      = 0.3ml of CO2 /100ml blood




                               Tanveer Raza MD MS MBBS
                                       razajju2@yahoo.com
Forms in which CO2 is transported
In Combination with Hb and Plasma Proteins-
  Carbaminohemoglobin
                            20% of total

   CO2 + amine radicals of Hb = CO2 Hgb
    (carbaminohemoglobin)

   Reversible reaction. CO2 is easily released into
    alveoli




                                     Tanveer Raza MD MS MBBS
                                             razajju2@yahoo.com
THANK YOU




        Tanveer Raza MD MS MBBS
                razajju2@yahoo.com

				
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posted:7/30/2011
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