Ch 13. Gas Transfer in Air (Lungs and Other) Flashcards
2 things a gas-transfer system is influenced by
properties of the respiratory medium
requirements of the animal
why is there such a big difference between lungs and gills
density and viscosity of water is 1000x that of air
water contains 1/13th as much O2 as air
major difference btw lungs and gills
lungs: bidirectional movement of air into and out of the lungs
gills: unidirectional movement of water over the gills
design objectives of gills
minimize diffusion distance
thin layer of water over the respiratory surface
what does subdivision of the lung improve
increase in respiratory surface area per unit volume
alveoli
many interconnected sacs that allow gas transfer to blood
air ducts leading to respiratory portion of the lung are lined with _____
cilia
mucus is secreted by epithelium of ducts and moved by cilia to keep lungs clean
type II cells
in lung epithelium
produce surfactants
mixing of gases in ducts and alveoli occurs by what
diffusion
convection currents from breathing
swan have really long necks…
high anatomic dead space so they have a larger tidal volume to maintain gas partial pressures
amphibian Amphiuma
rises to the surface once an hour to breathe b/c it is preyed upon at the surface
tidal volume more than 50% of total lung capacity
large, slow oscillations in PO2
O2 and CO2 levels in alveolar gas are determined by what 2 things
ventilation (breathing rate, tidal volume, anatomic dead space)
rate of gas transfer
pulmonary circulation
deoxy blood from pulmonary artery enters the lung and gathers O2 and releases CO2
in birds and mammals are blood pressures in the pulmonary circulation LOWER than those in systemic circulation?
yes
reduces filtration of blood into the lung
why is there excessive lymph drainage from the lung
make sure fluid doesn’t collect so diffusion distance isn’t increased
sheet flow
describes blood flow through pulmonary circulation
blood between two parallel surfaces of pulmonary capillaries
if blood pressure increases, what happens to the sheet flow
the capillariy layers separate, leading to a thicker blood layer
the lung apex is _______ than the base
higher
low flow to apex when vertical
more even flow distribution when horizontal
if transmural pressure is negative
capillaries collapse and blood flow stops
what does arterial blood pressure represent
blood flow
increases with distance from lung apex –> open capillaries and more flow at the base of the lung
does reduced O2 levels/low pH cause vasoconstriction or vasodilation of pulmonary blood vessels
vasoconstriction
so blood will flow to better ventilated areas
hypoxic pulmonary vasoconstriction via K channels
rapid onset due to inhibition of K channels, smooth muscle depol, and Ca release
lung elasticity creates a pressure _______ atmospheric in the fluid-filled pleural space
below
gas transfer in bird lungs
when breathing, volume changes in thoracic and abd air sacs, not the lungs
squeezing of air sacs moves air through parabronchi tubes
valving in bird gas exchange
bidirectional flow through mesobronchus
unidirectional flow through parabronchi
over 70% of the lung wall’s resistance to stretch is provided by
surface tension of fluid
surfactants
lipoprotein complexes made by type II cells that give a low surface tension
4 surfactant functions
low surface tension of alveoli so inflation is easier
prevent alveoli from sticking when deflated
so newborn babies can inflate lungs
reduce blood flow resistance
3 things to do if a newborn doesn’t have surfactants (usually premature)
force air into lungs with positive pressure
surfactant replacement
pregnant women given cortisol injection –> stimulate type II cells in the fetus
does increased lung ventilation cause increased heat and water loss?
yes
cool, dry air entering the lungs is…
humidified with water vapor from nasal mucosa
heated from contact with blood
nasal passage temperatures
cool at the tip and warmer toward the throat
high blood flow in a countercurrent system to maintain temp gradient
why do animals exhale through the mouth
increase heat loss
at expense of water loss
do gills use a unidirectional water flow system
yes
valves in the buccal cavity and opercular clefts maintain this
why do water-breathing animals need a much higher ventilation rate
because the O2 content in water is much lower
uses more energy
operculum
gill cover where water exits
pathway for gill water flow
skeletal muscle pumps in the buccal and opercular cavities draw water into the mouth
passes over gills
exits through a cleft in the operculum
is there a higher pressure in the buccal or opercular cavities
buccal
helps ensure unidirectional flow
ram-ventilation
mouths are open while swimming to ventilate gills via forward motion
ex. tuna, remora
blood flow through fish gills
sheet flow - pressure inc = thickness inc
concurrent, countercurrent, or a combination
advantage of countercurrent blood and water flow
maintain a larger difference in PO2 so more gas is transferred
is the flow rate of water across gills higher than blood?
yes, but O2 content of blood is higher in fish
insect tracheal systems
air filled tubes - spiracles that are closed or open
insect tracheal system flow
spiracles –> trachea –> tracheoles –> fluid in tips for O2 diffusion into flight muscles –> fluid dispersed
diving insect O2 supply
air trapped in layers or body hair
from water
pO2 in air next to body is 100mmHg vs. pO2 of H2O is 150mmHg –> diffusion
