Assertion: giraffe | /r/UsedFor | valve
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text: This would be a problem (involving too high blood pressure) when the giraffe was head-down drinking water, were it not for a unique collection of reinforced artery walls, by-pass and antipooling valves, a web of small blood vessels (the rete mirabile, or ‘marvellous net’)1 and pressure-sensing signals that keep adequate blood flow to the brain at just the right pressure.