Respiratory faculties of aquatic craniotes

2019 ◽  
pp. 125-138
Author(s):  
Steven F. Perry ◽  
Markus Lambertz ◽  
Anke Schmitz
Keyword(s):  
Gas Exchange ◽  
Current Model ◽  
Muscular Activity ◽  
Cartilaginous Fish ◽  
Unidirectional Flow ◽  
Internal Fluid ◽  
Filter Feeders ◽  
Respiratory Mechanism ◽  
Counter Current ◽  
Branchial Region

This chapter introduces the ‘who has what’ in terms of water-breathing respiratory faculties for craniotes. A branchial basket and a ventral heart or hearts that perfuse the branchial region with deoxygenated internal fluid is part of the bauplan of all chordates, including craniotes. Cilia ventilate the branchial region of extant non-craniote chordates, which are also predominantly sessile or planktonic filter feeders. In craniotes, the gills are the main gas exchange organs. They are ventilated by muscular activity and perfused with blood that contains haemoglobin in erythrocytes and flows in the opposite direction to the ventilated water (counter-current model). In spite of major differences in the structure of gills and the ventilatory apparatus among jawless craniotes, cartilaginous fish, and bony fish, the basic push–pull, constant, unidirectional flow respiratory mechanism remains unchanged (of course, with a few notable exceptions). In addition, both the blood and the structure of the gills may reflect adaptations of the respiratory faculty to habitual living conditions.

Physiological dead space and effective parabronchial ventilation in ducks

1986 ◽  
Vol 60 (1) ◽  
pp. 85-91 ◽  
Author(s):  
R. H. Hastings ◽  
F. L. Powell
Keyword(s):  
Gas Exchange ◽  
Dead Space ◽  
Current Model ◽  
Arterial Occlusion ◽  
Physiological Dead Space ◽  
Pekin Ducks ◽  
Dead Space Volume ◽  
Effective Ventilation ◽  
Pulmonary Arterial ◽  
Cross Current

Gas exchange in avian lungs is described by a cross-current model that has several differences from the alevolar model of mammalian gas exchange [e.g., end-expired PCO2 greater than arterial PCO2 (PaCO2)]. Consequently the methods available for estimating effective ventilation and physiological dead space (VDphys) in alveolar lungs are not suitable for an analysis of gas exchange in birds. We tested a method for measuring VDphys in birds that is functionally equivalent to the conventional alveolar VDphys. A cross-current O2-CO2 diagram was used to define the ideal expired point (PEi) and VDphys was calculated as from the equation, VDphys = [(PEiCO2--PECO2)/PEiCO2]. VT, where VT is tidal volume. In seven Pekin ducks VDphys was 13.8 ml greater than anatomic dead space and measured changes in the instrument dead space volume. VDphys also reflected changes in ventilation-perfusion inequality induced by temporary unilateral pulmonary arterial occlusion. Bohr dead space, calculated by substituting end-expired PCO2 for PEiCO2, was insensitive to such inhomogeneity. Enghoff dead space, calculated by substituting PaCO2 for PEiCO2, is theoretically incorrect for cross-current gas exchange and was often less than anatomic dead space. We conclude that VDphys is a useful index of avian gas exchange and propose a standard definition for effective parabronchial ventilation (VP) analogous to alveolar ventilation (i.e., VP = VE--VDphys, where VE is total ventilation).

The bottom line

2019 ◽  
pp. 192-196
Author(s):  
Steven F. Perry ◽  
Markus Lambertz ◽  
Anke Schmitz
Keyword(s):  
Gas Exchange ◽  
Structure Function ◽  
Functional Result ◽  
Circulatory System ◽  
Arms Race ◽  
Food Sources ◽  
Bottom Line ◽  
Function Unit ◽  
Counter Current ◽  
Line P

This chapter summarizes the most important aspects of the entire book. Writing an abstract of a summary can result in a ‘bouillon cube’ of information that is nearly incomprehensible, so this sticks to the most far-reaching observations and conclusions. The structure–function unit referred to here as the respiratory faculty did not just suddenly appear, but rather bits and pieces of it are recognizable even in most basally branching metazoan lineages. The use of mitochondria in an aerobic atmosphere to produce large amounts of energy-carrying molecules precipitated a kind of arms race, whereby the individuals that could compete better for food sources or become predatory could become part of an evolutionary cascade. These new animals moved into another realm, but the old ones did not necessarily disappear: they just did what they always did, maybe a little better. In the most diverse lineages of invertebrates and craniotes we see similar changes appearing: gills with counter-current exchange, highly specialized oxygen-carrying proteins, a partly or completely closed circulatory system that includes the gas exchange organs, lungs. The more extreme the grounds for specialization, the more similar are these structures and functions. Often the functional result remains unchanged or becomes improved while the anatomical cause changes dramatically, but just as often structures change little but minor functions become major ones: a phenomenon called exaptation. This book has looked at most major animal groups and these principles turn up everywhere. It talks about multidimensional forces at work in a multidimensional world, and respiration is the keystone to it all.

A Cineradiographic Study of the Central Circulation in the Hagfish, Myxine Glutinosa L

1960 ◽  
Vol 37 (3) ◽  
pp. 469-473
Author(s):  
RAGNAR HOL ◽  
KJELL JOHANSEN
Keyword(s):  
Body Temperature ◽  
Blood Vessels ◽  
Muscular Activity ◽  
Active Part ◽  
Striated Muscles ◽  
Direct Communication ◽  
Myxine Glutinosa ◽  
True Blood ◽  
Central Circulation ◽  
Branchial Region

1. An angiocardiographic study has been made of Myxine glutinosa, using modern cineradiographic instrumentation. In addition to the heart, vessels in the branchial region have been studied. 2. The topography of the heart chambers and their filling and emptying have been described. The frequency of the heart at body temperature, 8-100° C., was found to be about 30 beats per minute. 3. Results are presented that support the assumption that the gill sacs and theirducts, as well as striated muscles in the branchial region, take an active part in the propulsion of blood. 4. The phenomenon of extravasation or circulation in lacunar spaces (blood sinuses in direct communication with the true blood-vessels) has been demonstrated. The described muscular activity in the branchial region seems to promote the return of blood from these sinuses to the heart.

Buoyant flow of through and around a semi-permeable layer of finite extent

2016 ◽  
Vol 809 ◽  
pp. 553-584 ◽  
Author(s):  
Tri Dat Ngo ◽  
Emmanuel Mouche ◽  
Pascal Audigane
Keyword(s):  
Capillary Pressure ◽  
Graphical Representation ◽  
Current Model ◽  
Gravity Current ◽  
Two Dimensions ◽  
Total Flux ◽  
Vertical Column ◽  
Fine Grid ◽  
Permeable Layer ◽  
Counter Current

The buoyancy- and capillary-driven counter-current flow of $\text{CO}_{2}$ and brine through and around a semi-permeable layer is studied both numerically and theoretically. The continuities of the capillary pressure and the total flux at the interface between the permeable matrix and layer control the $\text{CO}_{2}$ saturation discontinuity at the interface and the balance between the buoyant and capillary diffusion fluxes on each side of the interface. This interface process is first studied in a one-dimensional (1-D) vertical column geometry using the concept of extended capillary pressure and a graphical representation of the continuity conditions in the ($S_{L}$, $S_{U}$) plane, where $S_{L}$ and $S_{U}$ are the lower and upper saturation traces at the interface, respectively. In two dimensions, we heuristically extend the two-phase gravity current model to the case where the current is bounded by a semi-permeable layer. Consequently, the current is not saturated with $\text{CO}_{2}$, and its saturation and shape are derived from the flux and capillary pressure continuity conditions at the interface. This simplified model, which depends on $\text{CO}_{2}$ saturation only, is compared to fine grid simulations in the capillary-free and gravity-dominant cases. A good agreement is obtained in the second case; the current geometrical characteristics are accurately described. In the capillary-free case, we demonstrate that the local total velocity, which is, on average, zero because the flow is counter-current, must be considered in the total flux at the interface to obtain the same level of agreement.

scholarly journals Evolution of vertebrate gill covers via shifts in an ancient Pou3f3 enhancer

2020 ◽  
Author(s):  
Lindsey Barske ◽  
Peter Fabian ◽  
Christine Hirschberger ◽  
David Jandzik ◽  
Tyler Square ◽  
...  
Keyword(s):  
Expression Patterns ◽  
Cartilaginous Fish ◽  
Unidirectional Flow ◽  
Gill Chamber ◽  
Bony Fishes ◽  
Anatomical Difference ◽  
Oxygenated Water ◽  
Cartilaginous Fishes ◽  
Minor Sequence ◽  
Single Versus

SummaryWhereas the gill chambers of extant jawless vertebrates (lampreys and hagfish) open directly into the environment, jawed vertebrates evolved skeletal appendages that promote the unidirectional flow of oxygenated water over the gills. A major anatomical difference between the two jawed vertebrate lineages is the presence of a single large gill cover in bony fishes versus separate covers for each gill chamber in cartilaginous fishes. Here we find that these divergent gill cover patterns correlate with the pharyngeal arch expression of Pou3f3 orthologs. We identify a Pou3f3 arch enhancer that is deeply conserved from cartilaginous fish through humans but undetectable in lampreys, with minor sequence differences in the bony versus cartilaginous fish enhancers driving the corresponding single versus multiple gill arch expression patterns. In zebrafish, loss of Pou3f3 gene function disrupts gill cover formation, and forced expression of Pou3f3b in the gill arches generates ectopic skeletal elements resembling the multiple gill cover pattern of cartilaginous fishes. Emergence of this Pou3f3 enhancer >430 mya and subsequent modifications may thus have contributed to the acquisition and diversification of gill covers and respiratory strategies during gnathostome evolution.

Bird Respiration: Flow Patterns in the Duck Lung

1971 ◽  
Vol 54 (1) ◽  
pp. 103-118 ◽  
Author(s):  
WILLIAM L. BRETZ ◽  
KNUT SCHMIDT-NIELSEN
Keyword(s):  
Heat Load ◽  
Air Flow ◽  
Body Temperatures ◽  
Exchange System ◽  
Direct Route ◽  
Unidirectional Flow ◽  
Air Sacs ◽  
Flow Directions ◽  
Air Flows ◽  
Counter Current

1. A heated thermistor probe was designed to determine the direction of air flow in the respiratory system of birds. The probes did not significantly affect the respiratory rates, tidal volumes, or body temperatures of birds implanted with the probes as compared to unimplanted birds. 2. Air-flow directions were determined in the primary bronchus, the craniomedial secondary bronchi, and the caudodorsal secondary bronchi in the lungs of ducks which were either unanaesthetized and at rest, anaesthetized, or panting due to heat load. 3. The recorded air-flow directions suggested the following patterns of air flow in the duck lung for resting respiration. During inspiration air flows to the posterior air sacs directly from the primary bronchus (the most direct route), without passing through the tertiary bronchi, while air flows towards the anterior air sacs via the caudodorsal secondary bronchi and the tertiary bronchi (thus by-passing the most direct route, the craniomedial secondary bronchi connecting these sacs to the primary bronchus). During expiration air flows from the anterior sacs to the primary bronchus via the craniomedial secondary bronchi (the most direct route), but from the posterior sacs through the tertiary bronchi and through branches of the craniomedial secondary bronchi to the primary bronchus (by-passing the most direct route, the portion of the mesobronchus posterior to the craniomedial bronchi). 4. The patterns established for panting and anaesthetized respiration were very similar to those described for resting respiration. There was no indication of an effective shunt operating during panting to avoid excessive ventilation of the exchange surfaces of the lung. 5. Flow in the tertiary bronchi appeared to be in the same direction during both inspiration and expiration (from the caudodorsal secondary bronchi towards the craniomedial secondary bronchi). Such unidirectional flow would permit the operation of a counter-current exchange system, provided that the blood vessels are arranged appropriately around the parabronchi.

The Evolution of Unidirectional Pulmonary Airflow

Physiology ◽  
2015 ◽  
Vol 30 (4) ◽  
pp. 260-272 ◽  
Author(s):  
C. G. Farmer
Keyword(s):  
Gas Exchange ◽  
Respiratory System ◽  
Aerobic Capacity ◽  
Atmospheric Oxygen ◽  
Work Of Breathing ◽  
Large Body ◽  
Blood Gas ◽  
Gas Barrier ◽  
Unidirectional Flow ◽  
Selection For

Conventional wisdom holds that the avian respiratory system is unique because air flows in the same direction through most of the gas-exchange tubules during both phases of ventilation. However, recent studies showing that unidirectional airflow also exists in crocodilians and lizards raise questions about the true phylogenetic distribution of unidirectional airflow, the selective drivers of the trait, the date of origin, and the functional consequences of this phenomenon. These discoveries suggest unidirectional flow was present in the common diapsid ancestor and are inconsistent with the traditional paradigm that unidirectional flow is an adaptation for supporting high rates of gas exchange. Instead, these discoveries suggest it may serve functions such as decreasing the work of breathing, decreasing evaporative respiratory water loss, reducing rates of heat loss, and facilitating crypsis. The divergence in the design of the respiratory system between unidirectionally ventilated lungs and tidally ventilated lungs, such as those found in mammals, is very old, with a minimum date for the divergence in the Permian Period. From this foundation, the avian and mammalian lineages evolved very different respiratory systems. I suggest the difference in design is due to the same selective pressure, expanded aerobic capacity, acting under different environmental conditions. High levels of atmospheric oxygen of the Permian Period relaxed selection for a thin blood-gas barrier and may have resulted in the homogeneous, broncho-alveolar design, whereas the reduced oxygen of the Mesozoic selected for a heterogeneous lung with an extremely thin blood-gas barrier. These differences in lung design may explain the puzzling pattern of ecomorphological diversification of Mesozoic mammals: all were small animals that did not occupy niches requiring a great aerobic capacity. The broncho-alveolar lung and the hypoxia of the Mesozoic may have restricted these mammals from exploiting niches of large body size, where cursorial locomotion can be advantageous, as well as other niches requiring great aerobic capacities, such as those using flapping flight. Furthermore, hypoxia may have exerted positive selection for a parasagittal posture, the diaphragm, and reduced erythrocyte size, innovations that enabled increased rates of ventilation and more rapid rates of diffusion in the lung.

Active relocation in lepadomorph barnacles

2000 ◽  
Vol 80 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Michael Kugele ◽  
Andrew B. Yule
Keyword(s):  
Muscular Activity ◽  
Leading Edge ◽  
Comparative Morphology ◽  
Trailing Edge ◽  
Unidirectional Flow ◽  
Pollicipes Pollicipes

Comparative morphology of the cement delivery apparatus of three lepadomorph barnacles indicates that the lepadid Lepas anatifera is unable to relocate voluntarily, whereas the two scalpellids Pollicipes pollicipes and Capitulum mitella can. Mean relocation speeds of up to 50 μm d−1 were measured for both scalpellids, which are probably underestimates of maximal rates given the absence of a directed stimulus. In the laboratory neither gravity nor unidirectional flow proved effective stimuli in directing scalpellid relocation. The two scalpellid species use quite different mechanisms to effect relocation at a leading edge of the base, although both slough basal material at the trailing edge. It is suggested that basal growth effectively accounts for the mobility of P. pollicipes but C. mitella is likely to employ muscular activity.

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