Vertebra S5

The sacral vertebra S5 (5th sacral vertebra) is the fifth and most caudal vertebra in the sacrum, which is formed by the fusion of five sacral vertebrae. The S5 vertebra is characterized by its smaller size compared to the other sacral vertebrae and its unique anatomical features.

The S5 vertebra typically exhibits inferiorly-projecting cornua and a kidney-shaped inferior body articular surface, which distinguishes it from the coccygeal vertebrae that follow it. The sacral canal, which houses the sacral nerves, narrows significantly at the level of S5 and terminates at the sacral hiatus. The sacral foramina, which allow the passage of the sacral nerves, are present on both the anterior and posterior aspects of the sacrum, with the foramina at the S5 level being the smallest.