Transport of Oxygen

Oxygen is transported from the respiratory organs to the tissues mainly by the respiratory pigment, hemoglobin (Hb).

Oxygen which is acquired during respiration diffuses from the alveoli of the lungs into blood due to its high concentration in alveoli. Hemoglobin of the red blood corpuscles has great affinity for oxygen. In blood, oxygen combines with hemoglobin to form an unstable reversible compound called oxyhemoglobin.

When blood reaches tissues, HbO₂ dissociates into hemoglobin and oxygen due to lower oxygen levels in the tissues, and the oxygen released diffuses into the cells. According to Bohr effect, the variations in the partial pressure of CO₂ in the tissues also helps in this dissociation.

Transport of CO2

CO2 is transported by blood from the tissues to the lungs. It is carried in the following forms:

1. Bicarbonate of sodium in plasma and potassium in red blood cells.

2. Carbaminohmoglobin in red blood cells.

3. Simple physical solution in plasma.

4. About 85% of CO₂ is transported in the form of bicarbonate.

From the tissues CO₂ diffuses into blood, and combines with water to form carbonic acid.

Since red blood cells contain the enzyme carbonic anhydrase which accelerates the reaction, most of CO₂ is collected in the RBCs than in plasma. Carbonic acid further dissociates into bicarbonate (HCO₃) and hydrogen ions (H+).

Most of the HCO₃ diffuses into plasma and reacts with sodium ions (Na+) to form sodium bicarbonate and is carried to the lungs.

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Table of Contents

17.0 - Introduction
17.1 - Gaseous Exchange and Transport

Chapter 18