State the function of the spiracle in the breathing mechanism of insects.
Answer:
Spiracles are air pores that connect the respiratory structure of insects with the external environment.
How do abdominal muscles help insects to breathe?
Answer:
• During inhalation, the abdominal muscles relax and the spiracle valves open. This reduces the internal pressure of the trachea causing air to be drawn into the trachea through the spiracle.
• During exhalation, the abdominal muscles contract. This increases the internal pressure of the trachea forcing air out through the spiracle.
State the two differences between the respiratory mechanisms of fish and humans.
Answer:
• Fishes have filaments and gills as their respiratory structures while humans have alveoli.
• The respiratory tract/opening of fish is the mouth and operculum while in humans, it is the nose.
Explain the mechanism of inhalation in humans.
Answer:
• The external intercostal muscles contract, the internal intercostal muscles relax.
• The action causes the rib cage to move upwards and outwards.
• At the same time, the diaphragm muscles contract and the diaphragm is lowered and flattened.
• Both movements cause the volume of the thoracic cavity to increase and its pressure to decrease.
• The higher atmospheric pressure outside forces air into the lungs.