Circulatory System Design

1. Open circulatory systems

a. Heart, blood vessels, and blood sinuses (homocoel)
b. Low pressure (5 - 10 mm Hg), low flow system
c. Distribution of blood is not well regulated
d. Typical invertebrate system

2. Closed circulatory systems

a. Blood combined within vessels |
b. High pressure (100 - 250 mm Hg), high resistance system
c. Elastic walls help sustain high pressure between heart - beats
d. Distribution of blood is well regulated
e. Typical vertebrate system (Exceptions: Cephalopods)

Functional Morphology of the Vertebrate Heart

• Structure of the heart varies in different vertebrates.
• Comparative analysis produces insight into the relationship between heart structure and function.
• The pulmonary (respiratory) circulation of birds and mammals are maintained by much lower pressures than in the systemic circulation since they have a series of heart chambers in parallel.
• Left side of the heart ejects blood into the systemic circuit.
• Right side ejects blood into the pulmonary circulation.

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