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outline 16

Comparative Physiology- Renner Lecture 16

QuestionAnswer
since simple diffusion isn't enough to provide adequate gas exchange, animals have evolved mechanisms that increase rate of diffusion, what are they 1. increase surface area for exchange (respiratory surfaces) 2. forced movement of gas or bulk transport of gas (ventilation and circulation)
adaptations to enhance surface area include 1. tracheal system in insects 2. gills and lungs
internally, how is surface area accomplished ? by extensive capillary networks
what helps enhance pressure gradient ? the use of hemoglobin and bicarbonate/carbonic acid, interconversion between diffusible and bound gas
gas in this form does not contribute to pressure gradient because it prevents equilibration and maintain gradient bound form
why do bound gases not contribute to pressure gradient because they prevent equilibration and maintain gradient
what are the three general forms of respiration? tracheal system in insects gills in fish lungs in terrestrial vertebrates
how is gas transport mediated in insects? by an exchange organ that is in close proximity to the cells
how is the proximity of the gas exchange organ to the cells is achieved in insects? by a series of highly branched tubes that are intermittently open to the outside
segmentally located openings along the thoracic or abdominal lateral body wall of insects spiracles
in insects, spiracles are open or closed via spiracular muscles
when are spiracles open? spiracles open in response to high CO2 and low pH of body fluids
when are spiracles closed? in dry conditions, closing limits loss of water
define trachea air conduits that branch extensively throughout the body and terminate in tracheoles
why are trachea lined with cuticle to prevent collapse
define tracheoles blind ended tubules that provide the major site for gas exchange
diameter of tracheoles 0.1 micron
cells are present within ____________ of any tracheole ending. Tracheoles are _____________ cells distant 30 microns, 2-3
where are tracheoles densely distributed? tissues with high metabolic requirement
the ends of tracheoles are _____________________ fluid filled
what is the purpose of having the tracheoles be fluid filled? it represents a balance between hydrostatic and osmotic pressure
in insects, at rest, where is tracheole fluid favored? hydrostatic pressure favors fluid in, osmotic pressure favors fluid out
in insects, when activity is increased, how does that affect the fluid in the tracheoles? osmotic pressure decreases fluid level in the tube
why is fluid decreased in the tracheole by osmotic pressure during activity? because a gaseous environment favors faster diffusion relative to diffusion in liquid
mechanism that aids in respiration found in larger insects and during flight to provide bulk gas transport ventilation
ventilation is accomplished by the presence of air sacs that are associated with the larger trachea
at rest most insects do not rely on ventilation of tracheal system and simply rely on ________________ for gas exchange simple diffusion
how do bees ventilate during flight? air sacs are compressed and expanded in response to muscle contraction/relaxation. That cycles during activity
what are benefits of ventilating during flight in bees? 1. cycles of air sacs compressing/expanding relative to muscle contraction/relaxation during activity 2. reduces diffusion distance by bringing in fresh air and removing "old" air from trachea
how does ventilation reduce diffusion distance ? by bringing in new air and removing "old" air from trachea
most aquatic insects use __________________ with adaptations for living in an aquatic environment an air filled tracheal system
what are the two adaptation in aquatic insects regarding the tracheal system? 1. using direct air intake by having spiracles located an one end of the body 2. using air bubbles as gas gills. Bubbles are trapped by hydrofuge hairs (hydrophobic) and are in contact with spiracles
how are air bubbles used as gas gills? bubbles are trapped against spiracles, bubbles contain O2. As O2 is used, its concentration in the bubble is decreased. O2 diffuses from the water into the bubble
how does CO2 not accumulate in the air bubble ? CO2 entering the bubble diffuses readily into the water due to it being more soluble than O2
how longs are air bubbles good for? ~ 7 hours
what are some limitations of water as a respiratory medium? 1. Gas diffusion in air much faster than in water 2. water is more viscous increasing the energetic cost of ventilating 3. low solubility of O2 in water 4. O2 tension varies in bodies of water 5. presence of sediments and decaying matter depletes O2
why is water more viscous than air at atmospheric pressure: mass of air/mL=0.0012g/mL water= 1g/mL
why does water respiration cost more energy? due to the low solubility of O2 in water, more water has to be moved across the respiratory system than air to obtain equivalent O2
1L of water has _______ of O2 1 L of air contains _________ of O2 7mL 209mL
respiration in humans costs ________ of metabolism for gas exchange in fish, it costs _________ of metabolism for respiration 1-3%, 10-20%
what are the sources of O2 in water? 1. from atmosphere 2. photosynthesis
where is the highest O2 tension present in bodies of water? O2 tension near the surface is greater than in deep water
why is deep water low in oxygen? dark no photosynthesis
why are lakes more likely to encounter O2 depletion? due to thermal stratification
what is thermal stratification? Temp in upper water increases, decreasing density which decreases layer mixing. Also known as summer fish kill
why does ag runoff, fertilizers, and sewage cause O2 depletion? because it increases bacteria, fungi and algae which consume O2 in water causing fish kill
the outer covering of the gill structures operculum
function of the operculum protecting the gills
what is beneath the operculum rows of gill filaments on four arches that form V
these structures are perpendicular to the gill filament secondary lamellae
these are 10-40 mm and form sieve between oral and operculum cavity increasing the surface area for gas exchange lamellae
functional unit in gas exchange lamellae
how are the lamellae equipped to function in gas exchange? thin walls dense capillary network both of these provide minimum barrier for diffusion ~ DeltaX= 0.6-6 microns
direction of water flow in teleost fish mouth>buccal cavity>across gills>out the operculum
how is water forced across the gills in teleost fish buccal floor raises increasing pressure in buccal cavity
what happens when the opercular cavity expands? pressure in the opercular cavity decreases to below pressure in buccal cavity driving water from buccal cavity across gills to opercular cavity
how does water from the outside not enter the opercular cavity when P is decreased blocked by valves
how is H2O discharged from the operculum by raising the floor of buccal cavity to increase pressure which will instantly increase pressure in the opercular cavity which will open the valves in opercular cavity causing H2O to exit
rate of the continuous ventilation is determined by activity level O2 tension in water, increase in low O2 tension in H2O
Created by: rusulali97