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Unformatted text preview: i. Arteries- (have thick muscle) move blood away from the heart 1. No valves ii. Arterioles- (have sphincter that help constrict and redirect blood flow-located right before the capillary networks) iii. Capillaries iv. Venules v. Veins-(have thin muscle)- 1. Function move blood back to the heart 2. Structure- veins have valves a. One way valves- forces the blood in a positive direction and prevents from moving back down. i. when get older valves get weaker 1. third more volume every time heart contracts. 3 chamber heart gives way for lungs Amphibians breathe through skin- Atrium# Ventricle# Grasshopper-malphegian tube...
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- Fall '08
- single loop, circuit bc blood, fish lack lung