Circulation & Respiration Flashcards
Diffusion is sufficient for organisms measuring…
<0.5mm
Respiratory organs
Skin, gills, lungs
Vertebrates that respire via skin are…
Lungless salamanders 100% - low metabolism and moist environment
Lake titicaca frog 100% - bottom of lake, skin folds increase SA
Most amphibians, some fish and some snakes
Why do organisms living in water need gills
Respiration in water is challenging, low solubility
1L of air contains ~210cm O2
1L of water contains ~10cm O2
Adaptations of the gills
1) continuous steady water flow = more energy efficient
2) large SA
3) countercurrent exchange
Dual pump overview
Using buccal and opercular cavities via lowering and raising the floor of the buccal cavity, and movement of the operculum allows continuous flow throughout the cycle to avoid O2 depletion at gill surface and minimise acceleration/deceleration of water
Counter current system
O2 of blood exiting lamellae approaches that of incoming water
Efficient - 90% extraction
Ram ventilation
Used when an organism is swimming with mouth open at high swim speeds
Gas bladders
Mainly bony fish
Dorsal out pouch of gut
Mainly buoyancy but sometimes respiratory
Aspiration pump/lungs overview
Reptiles mammals birds
Air is drawn into the lung, not forced
Allows feeding and respiration to be functionally uncoupled
Avian respiration
Resting metabolic rate is similar to other vertebrates, flight requires higher O2 consumption
- Ventilation
Paired lungs in thoracic cavity
Anterior and posterior sacs among viscera and within bones
movement of sternum causes compression/expansion of rib cage which acts on air sacs
Lungs themselves don’t change shape - Gas exchange
Parabronchus contains air capillaries
Air flows through
Very thin air-blood interface minimises diffusion barrier
(Mechanical strength from air capillaries)
Capillaries arranged in parallel = cross current system - more efficient as respiratory air always meets deoxygenated blood
High fliers require a higher metabolic rate as air is thin and po2 low so... Enhanced hypoxic response Larger lungs increase SA Haemoglobin has higher infinity Mitochondria closer to capillaries
Water to land transition & evolution of respiratory systems
Evolved independently
Mainly in freshwater pools prone to seasonal hypoxia
Ventral lungs evolved prior to dorsal gas bladders
Most fishes = dual pump
Air-breathing fishes = buccal pump
Amphibians = modified buccal pump
Reptiles birds mammals = aspiration pump
Dual pump description
Water ventilation, water breathing fishes
Gnathostome system
Buccal & opercular pumps work in a synchronous pattern
Unidirectional flow
Gill curtain between the two pumps
Dual pump, muscular mechanisms
1) first stroke/suction phase:
- buccal and opercular valves compressed with closed oral and opercular valves
- buccal cavity expands = low intraoral pressure
- oral valves open, outside water rushes in following the pressure gradient
- at the same time, the opercular cavity expands but the valve is still closed = pressure lower than buccal cavity
- water crosses gill curtain into the opercular cavity
2) second stroke/force phase
- oral valves close, opercular valves open
- simultaneous muscle compression of both cavities raises pressure
- opercular pressure is lower as the valve is open and water exits
Buccal pump description
Air ventilation, used by air breathing fishes and amphibians
Ventilates lungs
Mouth cavity expands to fill with fresh air