Assertion: giraffe's head | /r/HasProperty | lowered
Facets:
Source sentences:
text: The jugular veins contain several (most commonly seven) valves to prevent blood flowing back into the head from the inferior vena cava and right atrium while the head is lowered.
text: A giraffes circulatory system is also specially modified, because the high pressure needed to pump blood up to its head could cause brain damage when the head is lowered.
text: To compensate for the sudden increase in blood pressure when the head is lowered, the giraffe has very elastic blood vessels and valves in the venous system of the neck.
text: The jugular veins in their necks have one-way valves which prevent excess blood flow to the brain when the head is lowered
text: When the head is lowered, special shunts in the arteries supplying the head restrict blood flow to the brain, diverting it into a web of small blood vessels (the rete mirabile or ‘marvellous net’).
text: Valves in the jugular veins also prevent returning blood from flowing backward while the head is lowered.
text: The neck vessels are equipped with numerous one-way valves that prevent blood from back flowing to the brain when the head is lowered, and muscle fibers surrounding the veins slow the flow of blood when the head is raised again.