Mechanism of Gaseous Exchange in Insects
(a) Inhalation
This involves air being drawn in through the thoracic spiracles.
This occurs when the abdominal muscles relax causing an increase in the abdominal volume and decrease in the pressure.
The valves in the thoracic spiracles open air is drawn in. they then close and due to muscle movement, air is forced along the tracheal system.
(b) Gaseous exchange
Oxygen dissolves in tracheal fluid and diffuses into the tissues due to diffusion gradient. Carbon (IV) oxide diffuses from the tissues to the tracheal fluid due to diffusion gradient.
(c) Exhalation
This involves air being drawn out through the abdominal spiracles. This occurs when the abdominal muscles contract causing a decrease in the abdominal volume and an increase in the pressure. The valves on the abdominal spiracles open while those of the thorax close due to muscle movement air is forced out.