Zy­gapoph­ysis: growths, yokes and joints

The Weekend Australian - Travel - - Health -

What are they? The bones in our spine (ver­te­brae) have growths that stick out and join to other ver­te­brae above and be­low. Th­ese growths are called zy­gapophy­ses — the sin­gu­lar is zy­gapoph­ysis. Why the name? Be­cause they link ver­te­brae, they are named af­ter the Greek word zy­gon , mean­ing yoke. The rest of the name comes from apo , mean­ing from, and ph­ysis , which means growth. What do they do? They pro­tect the spine by mak­ing it more stable. Each zy­gapoph­ysis locks onto the ad­ja­cent ver­te­bra at a facet joint, of which ver­te­brae typ­i­cally have four. Th­ese joints are po­si­tioned at each level in the spine to en­sure the ver­te­brae ro­tate just as much as needed, and also don’t slip for­ward over each other. For ex­am­ple, be­cause we need to turn our head, they al­low much more ro­ta­tion in the bones in our neck than in the lower back.

Il­lus­tra­tion: Nathalie Gar­cia

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