How many articulating surfaces are on the equine sacrum?

How many articulating surfaces are on the equine sacrum?

• A. 6
• B. 8
• C. 7
• D. 9

Answer: (B)

Articulating surfaces are the contact facets where bones form joints. The horse’s sacrum is made by fusing five sacral vertebrae. Between each pair of adjacent sacral vertebrae there are articular surfaces, and there are four such boundaries: S1–S2, S2–S3, S3–S4, and S4–S5. Each boundary provides two articular surfaces (left and right facets) on the sacrum that participate in these vertebral joints. So, 4 boundaries × 2 surfaces each = eight articulating surfaces in total on the equine sacrum. This count reflects the vertebral articulations within the sacrum itself, not its connections to the pelvis or tail.

Articulating surfaces are the contact facets where bones form joints. The horse’s sacrum is made by fusing five sacral vertebrae. Between each pair of adjacent sacral vertebrae there are articular surfaces, and there are four such boundaries: S1–S2, S2–S3, S3–S4, and S4–S5. Each boundary provides two articular surfaces (left and right facets) on the sacrum that participate in these vertebral joints. So, 4 boundaries × 2 surfaces each = eight articulating surfaces in total on the equine sacrum. This count reflects the vertebral articulations within the sacrum itself, not its connections to the pelvis or tail.