passive diffusion. due to partial pressure across an exchange surface.
limited by 1. surface area - thin, multi-branching gills, lungs, from sacs to aveoli 2. must work with circulatory system (a second pump) 3. resistance by the tissue barrier - a thin moist membrane
cellular and chemical respiration
deriving energy from aerobic breakdown of fuels. delivery of O2 to the tissues and removal of CO2
exchange between environment and blood
exchange between tissues and the blood
active movement of the respiratory medium (air or water) across the exchange surface (barrier between the blood and the environment
ventilation in water. unsuitable for breathing in air (collapse without water). one way flow of water.
associated with the pharyngeal arches, slits, and pouches. covered with interbranchial septa (elasmobranchs). osteichthyans: opercula
larvae, some adult amphibians (neotony)
adaptation for breathing air. all internal. true one is ventral to digestive tract, arise as outpocketings of the gut (endoderm), glottis, trachea, tronchi, bronchioles
freash air for exchange
tidal volume - dead space
tidal volume + residual volume
usually a single sac. dorsal to the digestive system. same embryonic origins as lungs. dual functions, not mutually exclusive, unclear origins, buoyancy and gas exchange. "lungs" found in one placoderm species. no lungs or gas bladders in agnathans or elasmobranchs
different contributions in different organisms. amphibians - plenthodontidae, no lungs or gills. humans - mostly CO2 loss upto 5%. bats - eliminate upto 12% of CO2 through wing membranes. reptiles - very little (scales)
the chorioallantoic membrane
amniotic (bird and reptile) eggs. highly vascularized, adjacent to the porous shell.
ventilatory mechanisms for prochordates and larval agnathans
relatively passive ventilation
external gills, ram ventilation (as swimming opens mouth, goes through and come out of gills)
active movement. dual pump - buccal and opercular: work in series, suction phase - force phase, water ventilation
pulse pump. forces air into lungs of gas bladders (2 or 4 stroke)
amniotes. lungs filled by negative pressure, muscular pump consists of abdominal muscles, intercostals, diaphragm. buccal cavity is no longer a ventilatory organ - feeding and respiration "decoupled"
cilia in larvae, gills are medial to branchial arches instead of lateral (larvae), velar pump and muscular pharyngeal pouches in adults. parasitic adult lamprey: 2 way pump when attached to host.
gill lamellae are lateral to branchial arch: holobranch, hemibranch, respiratory unit. 2 stage buccal/parabranchial pump provides constant flow from pharynx, over gills, through gill slits. intake through spiracle allows for breathing when sub-terminal mouth is on substrate.
arch and lamellae
half of holobranch
2 facing hemibranchs
lateral gills are V shaped, lamellae are subdivided. bony or cartilaginous operculum covering the branchial arches - allows for a dual (buccal and opercular) pump. swim bladders and gas bladders. air bladders
for air-breathing, sound amplification (hearing), sound production (communication)
lung fish ventilation
small interconnected compartments
ventilations depends on buccal and pharyngeal pumping - no diaphragm or ribs. gills - some not all adults, most larva, not all, internal or external. lungs - most, not all adults. septal: increased surface area, faveoli, more gas exchange in anterior, less in posterior. adaptations in larvae to increase efficiency of buccal pumping and to attach to surfaces.
highly keratinized epidermis make cutaneous respiration impractical, well-developed lungs with numerous faveoli, muscular pumping (aspiration) from intercostal and other somatic muscles, occasionally, passive expiration. posterior portion of lungs often less divided and less vascularized, greater contribution from anterior
intercostals contract to expand ribs. diaphragmatic muscles (connected to posthepatic septum) move the liver like a pison. gastralia.
left lung is reduced or lost. elongated opening to trachea ("trenchlike")
ribcage cannot expand due to the rigid shell. internal sheets of muscles contract and expand to aspirate the lungs (diaphragmaticus, others in tortoises attach to limiting membrane, move it to change internal pressure). cutaneous exchange during hibernation.
well-developed lungs with bronchioles terminating in alveoli, muscular diaphragm as muscular pump - passive exhalation due to elatic recoil. tidal (2 way) breathing with residual volume.
no cutaneous respiration. trachea, paired lungs, muscular aspiration pump. air sacs (non-respiratory tissue) attached to respiratory system. increased surface area not due to alveoli or faveoli but rather a series of fine tubular passages called parabronchii with tiny tubes called air capillaries. one- way system.
dead-end sacs, very thin, for gas exchange. very extensive increase in surface area (10x reptiles)
tiny tubes that are the site of gas exchange
fish gas transfer
countercurrent. most efficient transfer of gases.
bird gas transfer
cross current. very efficient transfer of gases. no residual volume.
lung gas transfer
faviform or alveolar. uniform pool. stable gas concentrations
ventilation: perfusion ratio
amount of O2 available: amount taken in. rate of ventilation needs to match the rate of gas exchange and circulation to be efficient. diffusion slower in water, water harder to move than air. V:P lower in air. Fish 35:1. Reptiles 5:1. mammals 1:1
ventilation in water
highly efficient countercurrent flow. high (>80%) extraction of oxygen. high metabolic cost. CO2 highly soluble in water.
ventilation in air
tidal breathing less efficient. lower (25%) efficiency oxygen extraction. lower cost metabolically.
acid base regulation
elimination of CO2 is another huge hurdle to overcome in order to breathe air. need to eliminate H+ to maintain pH balance and oxygen-carrying capacity of hemoglobin