The Transport of Oxygen in the Human Body
The diffusion of oxygen from the alveoli into the blood capillaries
1. During inhalation, air is taken into the lungs through the nasal cavity, passing through the trachea, bronchi, bronchioles and finally alveoli.
2. The air that reaches the alveoli is called alveolar air. It is rich in oxygen and poor in carbon dioxide.
3. The blood that reaches the capillaries surrounding the alveoli is poor in oxygen and rich in carbon dioxide.
4. Gas exchange takes place in the lungs by diffusion.
5. Oxygen diffuses from the alveoli into the red blood cells in the capillaries.
6. At the same time, the red blood cells in the capillaries release carbon dioxide which diffuses into the alveoli.
The transport of oxygen by blood
1. Red blood cells contain the oxygen-carrying pigment called haemoglobin.
2. Oxygen combines with haemoglobin to form oxyhaemoglobin.
3. The blood cells are transported around the body.
The diffusion of oxygen from the blood capillaries into the body cells
1. Gas exchange also takes place between the capillaries and the body cells.
2. Oxygen has a higher concentration in the capillaries than in the body cells.
3. Carbon dioxide has a higher concentration in the body cells than in the capillaries.
4. Oxyhaemoglobin releases oxygen which diffuses into the body cells.
5. Carbon dioxide diffuses into the blood at the same time.