The plural of centrum; the central or principal part of a vertebra or other anatomical structure.
From Latin 'centrum' (center), derived from Greek 'kentron' (spike, point of a compass). In anatomy, 'centra' refers to the solid central bodies of vertebrae that support the spinal column.
Your spine is basically a stack of donuts with the 'centra' being the solid parts and the holes containing your nerves—if those centra get damaged, that's when you have serious back problems!
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