lecture 19 - respiration and gas exchange Flashcards
How does gas exchange occur in the simplest invertebrates?
gas exchange occurs across the entire surface of the organism and diffusion of gases is sufficient
What is bulk flow?
The movement of fluid and the gases carried by the fluid from respiratory surface to all cells
What is the role of ventilation in bulk flow?
movement of respiratory medium (air/ water) to respiratory surface
What is the role of diffusion in bulk flow?
movement of gases across respiratory membrane
What is the role of circulation in bulk flow?
movement of fluid (hemolymph / blood) to cells)
What are gills?
Outfoldings of respiratory membrane
O2 concentration in water is low (and even lower in warm, salty water)
Large surface area
Easy to keep moist
Structural variations
How does ventilation happen in fish?
by water passing through the mouth and over gills
operculum aids movement
What is countercurrent exchange?
blood and water flow in opposite directions maintaining a diffusion gradient across the whole gill lamallae so equilibrium is never reached - at every step there is always more oxygen than water in the bloodstream
How is gas exchange different in terrestrial animals?
Oxygen uptake higher in animals breathing air
- have energy requirements as they are more active
Oxygen content is 50 greater in air than water
The diffusion rate of oxygen is ~8000 faster in air compared to water
Water is more viscous so ventilation of respiratory membrane requires more energy
Water loss can be a problem - avoided by having internal respiratory surface
Describe the role of tracheae in gas exchange
Insects breathe via a tracheal system (air tubes that run throughout the body)
Open circulatory system not involved in transporting gases
All cells in close contact to respiratory medium – cells receive O2 via diffusion
Ventilation by rhythmic body movements
Air enters through spiracles
Largest tube is the trachea strengthened by chitin
Air flows through smaller tubes (tracheoles)
Air sacs near to cells with high O2 demand
Describe lungs
Present in mammals, birds, reptiles, amphibians and lungfish
Restricted to one location
Requires circulatory system to transport gases to cells
How do frogs ventilate their lungs?
When in water, respiration takes place through the skin
Mouth floor lowers, cavity size increases so air flows in
Mouth floor contracts forcing air into lungs
How do birds ventilate their lungs?
one-directional
series of tubes - parabronchi
Needs to be efficient to supply the high energy required for flight & also to extract sufficient oxygen at high altitudes (lower oxygen partial pressure)
