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)