ectotherms lecture 5 Flashcards
What is the mechanism of the buccal pump?
Water flows into the mouth cavity due to the dropping of the floor of both the buccal and opercular cavities
The buccal floor is then raised to force more water from the mouth cavity to the opercular cavity
The opercular cavity then contracts to force water out through the operculum
The cavities are then both opened again to allow flow of water in from the environment
What is the advantage of a buccal pump?
It ensures unidirectional flow of water increasing efficiency with which gaseous exchange occurs
It also uncouples the movement of the fish from its respiratory system allowing it greater diversity
What evolved first the swim bladder or the lung?
The lungs
What was the purpose of lungs?
On land gills are ineffective at respiration as they often collapse under their own weight and the surface tension of water causes the lamellae to stick together both of which reduce the surface area available for gaseous exchange
How does the swim bladder function?
This controls the ability of the fish to rise and fall in the water
They exist in two forms ones that are connected to the oesophagus which and one which is not connected to the oesophagus and instead has a gas gland (secretory epithelium next to a rete full of blood vessels) as blood passes passes this gland the drop on pH triggers the release of oxygen via the bohr effect causing a build up of oxygen and pressure in the swim bladder allowing the fish to rise (sinking is done by reducing the pH of the secretary epithelium)
What is the difference between a buccal and thoracic pump for ventilation?
The thoracic pump is a positive pressure pump while the buccal pump is a negative pressure pump
What is the breathing cycle in the frog?
Air is taken into the buccal cavity by lowering the floor of the mouth
Air is permitted to escape from the lungs passing over the buccal cavity
The external nares are closed forcing air into the lung
While air is retained in the lungs by the closed glottis the cycle can begin again by taking air into the mouth
What is the advantage of intercostals?
They allow a greater movement of the chest to allow for more expansion and therefore a greater pressure gradient drawing in air
They can also uncouple the breathing apparatus from the muscles used for movement allowing greater freedom to move quickly
What is unique about ventilation in a tortoise?
The carapace interferes with the intercostal muscles resulting in the animal needing to move to ventilate its lungs
What is the crocodilian version of the thoracic pump?
This animal uses its liver as a thoracic pump, bringing it closer to its pelvic girdle to expand the thoracic cavity and draw in air
What is the difference between the lung of amphibians and tetrapods?
Amphibian lungs, such as that of the salamander are often nothing more than simple sacs as much of the breathing is done through the skin
Tetrapods however have a much more developed lung which are more compartmentalised to allow a greater gaseous exchange area
