The Transport of Oxygen in The Human Body

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During inhalation, air is taken into the lungs through the nasal cavity, passing through the trachea, bronchi, bronchioles and finally alveoli. The air reaches the alveoli is rich in oxygen and poor in carbon dioxide. The blood from the heart that reaches the capillaries surrounding the alveoli is poor in oxygen and rich in carbon dioxide.

Oxygen diffuses from the alveoli into the red blood cells in the capillaries. At the same time , the red blood cells in the capillaries release carbon dioxide which diffuses into the alveoli.

Red blood cells contain the red pigment called Haemoglobin. Haemoglobin combine with oxygen to form oxyhaemoglobin. Oxyhaemoglobin from the lung is flow to the heart.

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When the oxyhaemoglobin from the heart reaches to the body tissue cell, oxygen has a higher concentration in the capillaries than in the body cells. So, oxyhaemoglobin releases oxygen which diffuses into the body cells. At the same time, carbon dioxide has higher concentration in the body cells than in the capillaries. So, carbon dioxide diffuses into the blood capillaries. Blood contain carbon dioxide next flow into the heart.

 

Source : http://www.tutorvista.com/content/biology/biology-ii/respiration/human-beings-gaseous-exchange.php