Three types of blood vessels arteries move blood away

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Unformatted text preview: a closed loop made up of blood vessels. • 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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