Circulation

1
Surfactants prevent alveolar fusing
water layer
thinner surfactant, more surface tension, higher
P
small radius, high P
large radius, lower P
P2x
surfactant layer
thicker surfactant, less surface tension, lower P
P1x
P1x
2
Birds have a unidirectional lung, unlike
mammals. What advantages might this have for O2
extraction?
3
Insect tracheae
Tubes for direct convection of air 1) Diffusion
faster so less convection necessary. 2) Can be
ventilated. 3) Fluid in tips reduce H2O loss. 4)
Pump fluid out if need more O2. 5) Can be used as
gills.
4
Bombyx silkworm breathing via spiracles
Why not leave the spiracles open all of the time?
PH2O
5
THE ANIMAL OF THE DAY (PhArthropoda, GeDysticus)
Trap a bubble of air under their wings. Oxygen
diffuses from the bubble into the tracheae.
What happens to the bubble? If Dysticus is
exposed to an atmosphere of pure O2 and is kept
in O2-saturated water, it drowns. Why?
How could it stay under longer?
Photo Tom Eisner
6
Air v. water for O2

• Air has high pO2 so air breathers are not
  affected by pO2 of air until 70 normal.
• ventilation rate changes little unless pCO2
  increases by a few .
• Water breathers very sensitive to pO2 of blood
  since it is a limiting substance
• will tolerate large pCO2 if pO2 of blood remain
  high (CO2 should easily diffuse away)

7
Vertebrate respiratory mechanisms
Efficiency of O2 extraction
8
Respiration extremes

• Comparative Animal Physiology

9
Ventilation/Perfusion ratios

• Perfusion ventilation blood capacity
• ventilate
  capacity

Air breather, e.g. mammal 5000 ml/min 5200
ml/min 200 ml/L / 210 ml/L Water breather, e.g.
fish 40 ml/min 4 ml/min 7 ml/L / 0.7 ml/L
10
Acclimation to altitude in mammals
Carotid bodies
? Hb affinity
??????????????? ventilation
? CO2
seconds
Bohr
? O2
?? pH)
(left shift)
Medulla chemorec
minutes
offset
1 week
erythropoietin
?????partial??? ventilation
??? HCO3
DPG ? Hb affinity
(norm pH)
days
(right shift)
? RBC
How do birds react?
? Hb
11
Caterpillar lungs
Hemolymph inc. O2 hemocytes are modified by
these tracheal tufts.
60 increase in hemocytes when hypoxic.
Other branches enter hemolymph to make lung.
12
Diving response

• Release stores (Hb, Mb)
• Redirect blood flow to high priority
• Also reduce cardiac output to keep B.P.
• Anaerobiosis
• Short-term only
• Inhibit inspiration
• Shut down lungs (why?)

13
THE ANIMAL OF THE DAY Emperor penguin, (ClAves,
Ge Aptenodytes)
Down keeps warm but Respiratory air sacs?
Reduced blood flow heart rate when submerged
Large blood volume blood has high O2 capacity
Muscles contain a lot of myoglobin. Usual dive
time 1-3 min. max. 15 minutes)
14
Gas secretion

• For air bladder during descent (100s atm).
• O2 secreted by blood via rete mirabile.
• Gas gland makes lactic acid.
• Root effect (fish) -- low pH -gt reduce Hb aff.
• Hb unloads O2 as enters rete low pH.
• Increased ionic concentration red. solubility.
• O2 goes to gas rather than solution.
• Counter-current exchange of CO2 bef. gland.
• Venous blood increase pH to increase Hb aff.
• How fill with N2?

15
Gas secretion

• Surface area of 100 cm2 in volume of droplet.
• 4-25 mm long exchange capillaries (Why?)

(higher)
Slower load!
(lower)