Biology 2672a: Comparative Animal Physiology Circulation.
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Biology 2672a: Comparative Animal
Physiology
Circulation
Why have a circulatory system?Diffusion sucks!Moves oxygen and
nutrients to cellsRemoves CO2 and waste
products from cells
How do I know it’s a circulatory system?PumpFluidVessels or spaces
Primitive circulatory systems
Open systems have all the characteristics of a circulatory system
The vessels in open systems can be quite elaborate…
Fig 24.24
Open Circulatory SystemsLow pressureRelatively inefficientCan’t keep interstitial fluids and
blood separateDon’t allow impressive athletic
feats
But what about insects? Insect flight muscle has the
highest work output in living organisms
Oxygen delivery (via the tracheal system) is decoupled from the fluid circulatory system
Box 23.3
Closed Circulatory System
From Heart
To Heart
Fig 24.11
Flow Rate through a system
Q = ΔPR
P2P1
ΔP=P1-P2Equation 24.3
Flow rate
Difference in pressure between the entry and exit to the system
Resistance in the system
Flow Rate
Flow rate can be determined by Pressure at the start of the system Pressure loss in the system Resistance in the system
Pressure is proportional to both flow rate and resistance
Q = ΔPR
Resistance in a system
R = 8 L ηπ r4
resistance length
viscosity
radius
Lr
Resistance
Longer systems have more resistance
More viscosity = higher resistance
Resistance is proportional to the 4th power of the radius of the tube A small change in tube diameter
= a huge change in resistance
R = 8 L ηπ r4
A teleost heart
Fig. 24.14b
Fish circulatory system
Heart
GillsBodyHead
Fig. 24.14a
What does this mean physiologically?
Heart
GillsBodyHead
Counter this with relatively large variation in heart size and performance
5 kPa
3 kPa
Heart oxygen demand may be a limiting factor in teleosts
Heart
GillsBodyHead
High performance fish heartsDeoxygenated blood perfusing
spongy myocardium is a limiting factor for fish
Salmonids, Tuna, Sharks have a ‘hybrid heart’.
Fig. 24.3c
(Most) Fishes Breathing Air
Electric Eel - Mouth
Plecostomus - Gut
Bowfin – Swim bladder Fig. 23.15
(Most) Fishes breathing airNo change to heart designAir breathing organs usually in
parallel with body tissuesDirect mixing of oxygenated and
deoxygenated blood Ensures adequate O2 for the heart(?)
Frog heart
Moyes & Schulte Fig. 9.15b
Frog circulation
Moyes & Schulte Fig. 9.11c
Selective distribution of oxygenated and deoxygenated blood
Cephalopod MolluscsRadiated 200 MyaHave a closed, divided
circulatory system
Fig. 24.20a
Oxygenated blood in heart
Oxygen delivery to octopus heart muscle
Fig. 23.3d
Octopus circulationTwo branchial hearts, one
systemicGills are in series with the
tissuesAllows oxygenated blood to be
pumped at higher rate through systemic tissues.
Circulation in mammals and birds
Fig. 24.10a
An untwisted mammalian circulatory system
Fig. 24.10b
End of material for mid-term
exam
Reading for ThursdayRegulation of Circulation
Pp 611-641 (continued)
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