How many sacral vertebrae are there?

How many sacral vertebrae are there?

• A. 3
• B. 4
• C. 5
• D. 6

Answer: (C)

The sacrum is formed by the fusion of several vertebrae, and in normal adult anatomy there are five of them. These vertebrae, labeled S1 through S5, fuse over time to create a single triangular bone that sits at the base of the spine and connects to the hip bones. Because fusion typically completes by late adolescence or early adulthood, the standard count you should learn is five. If you ever see three, four, or six, those numbers don’t match the usual anatomy, though rare variations like sacralization of L5 or lumbarization of S1 can alter how many segments are recognized in some individuals.

The sacrum is formed by the fusion of several vertebrae, and in normal adult anatomy there are five of them. These vertebrae, labeled S1 through S5, fuse over time to create a single triangular bone that sits at the base of the spine and connects to the hip bones. Because fusion typically completes by late adolescence or early adulthood, the standard count you should learn is five. If you ever see three, four, or six, those numbers don’t match the usual anatomy, though rare variations like sacralization of L5 or lumbarization of S1 can alter how many segments are recognized in some individuals.