Learning Objectives: Circulation in Animals (2/20/09). Compare the different methods of internal transport of body fluids within the context of maintaining homeostasis. Differentiate between open and closed circulatory systems, with examples.
This section begins on p. 994
Average time for a molecule (solute, gas, or water) to move a set distance (L)...
Directly proportional to the distance squared!
Note that the coelom in arthropods is present, but much reduced. Explain why the coelom is relatively large in annelids.
See also p. 995
Compare pressures in arteries, veins, and capillaries.
How is blood flow accomplished in veins?
In which tissues would you expect to find the most capillaries?
Jean Louis Marie Poiseuille (Poiseuille’s Law, ~1838)
Volume flow rate =
in a cylinder
…the concentrated movement of groups of molecules,
How does this affect resistance?
Is this a likely mechanism?
How would this be accomplished?
Volume flow rate =
Label the arrows
to show the net
direction of water
Label the diagram to explain the net direction of this bulk flow.
might change the
rate of filtration or
Do capillaries ever change their porosity?
Name one plasma protein that helps maintain the osmolarity of blood plasma.
(tail end)sinus venosus atrium ventricle truncusarteriosus(head end)
This is the circulatory scheme in bony fish
Which chamber receives blood first?
Most fishes have never solved this “problem”, which is probably why most of them are poikilothermic with relatively low aerobic capacity.
Venous return is facilitated by body movements.
While obviously adequate, this is not a very efficient system. The pressure generated by contraction of the ventricle is almost entirely dissipated when the blood enters the gills.
This group of marine invertebrates has solved the problem by having separate pumps:
* two gill (branchial) hearts to force blood under pressure to the gills
* a systemic heart to force blood under pressure to the rest of the body.
The Squid Hearts
How does this adaptation relate to the lifestyle of cephalopods?
Trace the pathway of a single
red blood cell, beginning at the
What causes the valves in the
heart to close?
What mechanisms enable blood
to be returned to the heart?
Describe the mechanical (physical) events in one cardiac cycle.
What feature of heart muscle is necessary for this coordinated function?
Why are there nerves that innervate the heart?
What chemical messages affect heart action?