respiratory systems Flashcards
what are the four possible steps in external respiration
1) Ventilation- co2/o2 movement from environmental movements, breathing
2) respiratory exchange- diffusion between a medium and internal bodily fluids at a respiratory
surface
3) circulation- bulk transport of the extracellualr fluid
4) cellular exchange= diffusion between extrcacellular fluid and intracellular fluid of the cell
How have body size, metabolism and habitat affected he evolution of external respiration
diffusion can supply the demands of a cell over a 1mm or less distance so small organisms simple diffusion in sufficient
1) size has increased in many phyla since first animals evolved so diffusion became to slow to cover distances in a reasonable time
= may have evolved dedicated gas exchange systems such as gills or lungs
2) Habitats vary in availability of oxygen from anoxic aquatic sea mud to sea level air
3) animals metabolisms vary in demand for oxygen with the highest demands arising in birds, mammals, some fishes and cephalopods and flying insects
how do respiratory adaptations enhance the limits of diffusion
1) bulk transport delays equilibrium formed between two non-moving fluids, ventilation, respiratory surfaces provided to keep continuous flow of air maintaining gradients
2) respiratory organs with high permeability, thin, increased surface area to increase diffusion rates
3) circulation- internal bulk transport aids diffusion in the same way as ventilation bringing about a continuous flow maintaining gradient
4) proteins in the circulatory fluid and inside some cells which convert gases between diffusible and no diffusible forms helping trap gases which can be released when needed, greatly increasing amount of gas circulation can carry
compare Tidal and flow through ventilation
1) tidal= external medium moved in and out through the same opening in two steps, inhalation and exhalation which is more inefficient as fresh and depleted medium mix
2) flow through = external medium enters one opening and leaves though another so fresh and depleted medium do not mix so fresh medium flow is almost continuous
what are some of the non-gill methods of gas exchange in aquatic animals
1) integument/cutaneous
- important to all amphibians and aquatic reptiles where gas exchange occurs via diffusion through the skin
Describe three examples of gills in different phyla
gill filaments of mollusc have cilia that create unidirectional respiration currents across filament surfaces
integuments and gills of most nudibranch contain noxious substances which they have stolen and used for protection as their gills are not protected
arthropod gills protected by their exoskeleton
what are gills
non-integument structures for gas exchange made up of invaginations of tissues protruding into the external medium with increased surface area, thin diffusion distances and highly circulated
How do fish create flow through breathing and how does gill counter current flow aid gas exchange
they use muscle systems for gas exchange
- water is pumped over gills by muscles in buccal and operculm muscles
- mouth opens and operculm shuts creating negative pressure causing oxygen rich water to enter
- mouth shuts and operculm constricts pushing water over the gills
= countercurrent means water and blood move in opposite directions maintain a conc gradient the entire length of the lamella for max absorption
compare how ventilation and gas exchange work in a land snail, spider and insect
land slugs and snails= require moist habitats relying on cutaneous exchange but snails can also use their mantle tissue under the shells, gas exchange is mostly diffusion
spiders= books lungs, stacked lamellae with air gaps between for exchange
insects = tracheae, systems of internal filled air tubes directly supplying tissues, reinforced with chitin, they are connected to the outside by spiracles and trachea break into finer branches called tracheoles
what are examples of bimodal and trimodal breathing and why did they evolve
Bimodal breathing refers to the ability of organisms to breathe both water and air mediums using gills and integumentary respiration e.g. tropical killifish which live in mangroves which that dry up
Trimodal refers to breathing water and air using lungs, gills and integument e.g. reedfish
compare respiratory systems of frogs and no avian reptiles including crocodilians
amphibians have bimodal lifestyles living in both land and terrestrial environments , in adult frogs have lungs which are simple and non compartmentalized, air enters from pharyx and branches into esphoagus, in larger species they can have alevoli but they are larger and less numerous
- air forced by buccal pump in the mouth, 02 mostly in lungs but c02 mostly through skin
- lizards and snakes rely only on rib muscle ventilation
compare mammalian and bird respiratory systems (structures and methods of ventilation)
to meet the increased metabolic demand the surface areas of the lung available needs to increase= done by increasing alveoli in mammals but in birds it is air capillaries
mammalian= airways begin in nasal passages into the pharynx to the trachea ( held open by Cartlidge rings) dividing into bronchi and bronchioles to alveoli (tension provided by surfactant) with minute pores of Kohn allowing airflow
avian= ventilation and gas exchange are separated due to air sacs and parabronchi with air capillaries, higher efficiency than mammals due to complete separation of ventilation and gas exchange functions, air capillaries are more narrow in size with shorter diffusion distance, flow through in one direction, rigidity- unlike alveoli diameter of capillaries doesn’t change through respiration cycle , so more resistant to damage and greater blood volumes
- cross current blood flow at the parabronchus, blood in capillaries becomes oxygenated
outline the air sacs in avian respiration
arise in the embryo producing an anterior and posterior group. anterior= received expelled air from the lungs, posterior= receives fresh air from trachea
- inflate and deflate tidally like mammals
- relies on rib movement in relation to sternum to power air sac ventilation
what is the function of external respiration and the types of gas movement
o2 uptake and c02 extrection
types of gas movement- exchange via diffusion or bulk transport
what are the challenges water breathers face
high viscosity and density
low oxygen solubility
low diffusion rate
