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In this case, however, it's going
from one big tube to many, many small tubes.
So, the
total cross-sectional area is much bigger. Also, the
resistance is
greaterfrom the friction
of rubbing against the walls.
c.
Blood flow through the tissues
When the oxygenated blood is gathered back together, the
pressure is still low. Circulation is slow and is helped
along by squeezing from the contraction of the swimming
muscles.
2.
Amphibians42.3 There is an
evolutionary trend towards the creation of 2 separate
loops; one for the deoxygenated blood and one for the
oxygenated blood.
Q.
What's the advantage of 2 loops?
- No drop in blood pressure
between heart and tissues
In
amphibians, there are 2 atria to take in blood, but only one
ventricle to pump it out.
Q.
What's the problem with this scheme?
- Mixing decreases the
amount of O2carried
to tissues and also makes gas
exchange less efficient (because the concentration
differences are less)
Solution
- a ridge inside ventricle reduces mixing
3.
Birds and mammals42.4 Birds
and mammals have developed 2 ventricles that completely
separate
O2-rich
and O2-poor
blood.
Q.What
are the advantages to 2 separate loops?
(a) No mixing, better
delivery of O2 to tissues
(b) better gas exchange in
lung (greater concentration difference)
(c) systemic and pulmonary
circuits can operate at different pressure
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