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Unformatted text preview: a closed loop made up of
• Three types of blood vessels:
• Arteries move blood away from the heart. Arteries divide into smaller arterioles.
• Veins carry blood toward the heart. Small venules join to become veins.
• The smallest blood vessels are capillaries. It is in the capillary bed that materials such as gases and
nutrients are exchanged.
• The two-chambered heart in fish moves the blood, but does not separate oxygenated from deoxygenated
blood. The three-chambered heart in amphibians and reptiles creates some separation of the blood (the
crocodile in particular has a partially-chambered ventricle). The four-chambered heart in mammals keeps
oxygenated and deoxygenated blood completely separate. This makes oxygen exchange more efficient and
allows for the high oxygen needs of heterotherms (“warm-blooded” animals).
• The heart beat consists of two contractions: the atria contract together, then the ventricles.
• When measuring blood pressure, the systolic pressure is pressure when the heart is contracted. The
diastolic pressure is the pressure when the heart is relaxed.
• The sy...
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- Winter '09