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GAS TRANSPORT

GAS TRANSPORT. OXYGEN(O2) & CARBONDIOXIDE(CO2). Gas Transport. O 2 which is taken up by the blood at the lungs is transported to the tissues for use by the cells. CO 2 produced at the cell level is transported to the lungs for elimination. Oxygen (O2) Transport.

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GAS TRANSPORT

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  1. GAS TRANSPORT OXYGEN(O2) & CARBONDIOXIDE(CO2)

  2. Gas Transport • O2 which is taken up by the blood at the lungs is transported to the tissues for use by the cells. • CO2 produced at the cell level is transported to the lungs for elimination.

  3. Oxygen (O2) Transport • Most of the O2 in the blood is transported bound to hemoglobin. Method of O2 Transport • Chemically bound to Hemoglobin – 98.5% • Physically Dissolved in plasma – 1.5%

  4. Oxygen Transport • Most O2 in the blood is transported bound to hemoglobin. Method of O2 Transport • Chemically bound to Hemoglobin – 98.5% • Physically Dissolved in plasma – 1.5%

  5. Oxygen Transport • Hb is present inside red blood cells [RBC]. • Hb is iron bearing protein molecule. • It makes reversible combination with oxygen. • When Hb combines with O2, we call Oxyhemoglobin [HbO2]. • Hb + O2 HbO2 • When O2 not combined with Hb, we call it reduced Hemoglobin or Deoxyhemoglobin.

  6. Gas Transport Hemoglobin promotes the net transfer of oxygen at both the alveolar and tissue levels. • There is a net diffusion of oxygen from the alveoli to the blood. This occurs continuously until hemoglobin is as much saturated as possible (97.5% at PO2 of100 mm of Hg). • At the tissue cells hemoglobin rapidly delivers oxygen into the blood plasma and on to the tissue cells. Various factors promote this unloading.

  7. Factors producing unloading of O2: • An increase in carbon dioxide from the tissue cells into the systemic capillaries increased hemoglobin dissociation from oxygen (shifts the dissociation curve to the right). • Increased acidity has the same effect. • This shift of the curve to the right (more dissociation) • is called the Bohr effect. • Higher temperatures also produces this shift, as does the production of BPG. • Hemoglobin has more affinity for carbon monoxide • as compared to oxygen.

  8. CO POISONING • Hemoglobin has more affinity for carbon monoxide(240 times) as compared to oxygen. • CO a poisonous gas, liberated by burning of carbon products, eg. automobile gasoline, coal, wood & tobacco. • Not detected, because it is colorless, odorless & non irritating and may be lethal.

  9. Oxygen-Hemoglobin (O2-Hb) dissociation(or saturation) curve

  10. Factors at the tissue level promoting the unloading of O2from Hb (Summary) • Shifting of O2 dissociation curve to right or more dissociation [giving] of O2 to tissues or less affinity of O2 for Hb. • The factors are 1- Increase PCO2 2- Increase Acidity [increase H+ ion] 3- Increase Temperature 4- Increase 2,3-BPG [bisphosphoglycerate] or 2,3-DPG [diphosphoglycerate]

  11. CO2 Transport • CO2 is transported in the blood by three ways: 1. Physically dissolved in Plasma- 10% 2. Bound to Hb- 30%Carbamino-Hb(Hb-CO2) 3. As Bicarbonate- 60%

  12. CO2 Transport Most carbon dioxide (about 60%) is transported as the Bicarbonate Ion. • Carbon dioxide combines with water to form carbonic acid. • The enzyme carbonic anhydrase facilitates this in the erythrocyte. • Carbonic acid dissociates into hydrogen ions and the bicarbonate ion. • 2-step, reversible process is favored at the tissue cells. • The reverse of this process (bicarbonate ions forming free molecules of carbon dioxide) occurs in the lungs. • 30% of the carbon dioxide is bound to hemoglobin in the blood. This is another means of transport. • About 10% of the transported carbon dioxide is dissolved in the plasma.

  13. Gas Transport Most carbon dioxide (about 60%) is transported as the Bicarbonate Ion. • By the chloride shift, the plasma membrane of the erythrocyte passively facilitates the diffusion of bicarbonate ions (out of the red cell) and chloride ions (inside of the red cell). • By the Haldane effect the removal of oxygen from hemoglobin at the tissue cells increases the ability of hemoglobin to bind with carbon dioxide.

  14. Abnormalities in Arterial PO2 Hypoxia • Condition of having insufficient O2 at the cell level • Categories • Hypoxic hypoxia (low arterial blood PO2) eg. high altitude, inadequate gas exchange • Anemic hypoxia (reduced O2 carrying capacity of blood) eg. Less RBC /Hb, CO poisoning • Circulatory hypoxia(too little oxygenated blood is delivered to tissue); Stagnant hypoxia eg. congestive heart failure or circulatory shock • Histotoxichypoxia (inability of cells to use O2) eg. cyanide poisoning Hyperoxia • condition of having an above-normal arterial PO2 • Can only occur when breathing supplemental O2 • Can be dangerous

  15. Abnormalities in Arterial PCO2 • Hypercapnia • Condition of having excess CO2 in arterial blood • Caused by hypoventilation • Hypocapnia • Below-normal arterial PCO2 levels • Brought about by hyperventilation which can be triggered by • Anxiety states • Fever • Aspirin poisoning

  16. Things to be learn from this lecture • Gas transport • Methods of O2 transport • Role of hemoglobin (Hb)in O2 transport • O2-Hb dissociation curve • Factors affecting Hb-O2 dissociation curve • Methods of CO2 transport • Abnormalities of PO2 & PCO2

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