Insect and Fish Respiratory System Flashcards
Describe the structure and function of gills.
Gills are the gas exchange of fish. They are composed of feather-like plates around which the water flows. Each plate has thousands of thin filaments. These filaments contain lamellae which are packed with capillaries and increase SA.
Describe the flow of water in relation to the flow of blood in the gills, and explain why this occurs.
Blood flows through the capillaries in a counter-current to the water to maximise gas exchange by maintaining a concentration gradient. If the flows were the same, then the equilibrium of oxygen concentration would be reached in the capillaries and gills, which would stop any more diffusion. The counter-flows maintain differing concentrations.
Describe the structure and function of spiracles.
Insects take in and expel gas through spiracles, or breathing pores. The spiracles have valves that allow them to open and close. This feature avoids exposure to the drying effects of the external environment.
Describe the structure and function of tracheal tubes.
Tracheal tubes carry gases from the spiracles directly to the cells within the insect. These tubes are kept open by spiral rings of chitin.
Describe the structure and function of the tracheoles.
The tracheal tubes branch into smaller tracheoles, which have a large SA:V. They are the sites of gaseous exchange, and their ends contain watery fluid that dissolves gases and allows diffusion.
Describe how gaseous exchange occurs in the gills.
The gills are directly exposed to the external environment, with water entering through the fish’s mouth, and leaving through the gill slits. Gaseous exchange of oxygen and carbon dioxide occurs in the gills. The gills need to be efficient as oxygen gas concentration is relatively low in water.
Describe how the gaseous exchange system of insects is regulated.
The number of open and closed spiracles controls the rate of respiration. The muscular movements of the thorax and abdomen help ventilate the system.
