Circulation & Respiration Flashcards
(21 cards)
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
Buccal pump - air breathing fishes - muscular mechanisms
Four stroke, with 2 main phases
1) inhalation phase
- mouth opens to intake (expansion [1]) atmospheric air
- compression [2] forces the bubble of fresh air from the buccal cavity into the lungs
2) exhalation phase
- transfer (expansion [3]) of spent air from the lungs into the buccal cavity -permitted by relaxation of the sphincter around the glottis in some fishes
- expulsion (compression [4]) of air from the buccal cavity to the outside either through the mouth or operculum
Bidirectional/tidal exchange
Helped by hydrostatic pressure?
- increases with depth
-fish rises to the surface with its head tipped upward = greater pressure on the body than the buccal cavity, so helps air be forced out in exhalation
-after fish has gulped atmospheric air and turned down, there is greater pressure on the buccal cavity than the lung = helps move air into the lung
Buccal pump - amphibians - muscular mechanisms
- pulse pump to ventilate lungs
- bidirectional flow
- two stroke (primitive and found in most)
- raises head above water, means there is hydrostatic pressure on the lung
- hypaxial muscles contact to actively aid exhalation (not inhalation)
- mouth closes and air exits through nostrils
Agnathans - lamprey - respiration
The feeding-ventilation current of water is produced by:
(1) pumps composed of muscular folds - velum
(2) compression and expansion of the brachial apparatus
Closure of velum and muscular contraction of the brachial apparatus forces water across the gills and out the pharyngeal slits
Pharyngeal openings are small and round - 7 pairs, covered by flaps of skin (valves)
Valves prevent retrograde flow as inward water movement forces them closed
Lie medial to the gills/brachial apparatus
- primary lamellae = gill filaments
- secondary lamellae = respiratory capillary beds
Countercurrent system
Agnathans - hagfishes - respiration
No major contributions of expansion and contraction of the brachial apparatus
Instead provided via scrolling/unscrolling of the velum and synchronised contraction/relaxation of the brachial pouches
Water enter via the nostril
Unidirectional flow
Elasmobranchs - sharks - respiration
Gills lie lateral to the brachial arch (as in all gnathostomes)
Primary lamellae on interbrachial septum
Dual pump
Maintain a nearly constant pressure difference between buccal (medial to gills) and parabrachial (lateral) cavities
Relatively lower in parabrachial = smooth, almost continuous unidirectional irrigation
Cross current
Spiracle - allows passage of water for gill irrigation, embryologically the first gill slit
Sharks in open water have ram ventilation that aids/replaces the dual pump
Bony fishes (teleostomi) - Osteichthyes - respiration
Operculum - bony or cartilaginous
Countercurrent
Adductor muscles cross between filaments to control the flow of water across the secondary lamellae
Gas bladders/lungs
