A reservoir or tank for storing water, or a fluid-filled cavity or sac in the body.
From Latin 'cisterna,' derived from 'cista' (box or chest), referring to a storage container. In anatomy, the term adopted this name because it resembles a reservoir or holding chamber.
Your brain has tiny cisternae (plural) that hold cerebrospinal fluid—they're like the water balloons protecting your brain and spinal cord from bumps and jolts.
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