- All the air that is inhaled through the nose does not get
involved in gaseous exchange.
- Some of the air remains in the conducting airways
(Nose, pharynx, trachea, bronchi).
- These regions are known as anatomical dead
space as no gaseous exchange takes place here.
- Also, the air reaching alveolar dead space
(the aveoli lacking capillaries around them) also cannot involve in
- Normal tidal volume is 500 ml. Only 350 ml of air
reaches the surface of gaseous exchange.
- 150 ml of the air remains in the dead
- The air present in dead space is exhaled without any
involvement in gaseous exchange.
Hence, all of the oxygen molecules found within inhaled air cannot
be exchanged with the alveolar-capillary blood.