**Question:** Structure crossing the dorsal surface of ischial spine are A/E:

A. Sacral spinous process
B. Sacral promontory
C. Sacrococcygeal ligament
D. Coccygeal arch

**Core Concept:** The ischial spine is a bony projection on either side of the ischium, one of the three parts of the pelvic bone. The dorsal surface of the ischial spine is where various structures pass over it.

**Why the Correct Answer is Right:** The correct answer, D, refers to the coccygeal arch, which is a bony arch formed by the fused coccygeal vertebrae. This structure crosses the dorsal surface of the ischial spine.

**Why Each Wrong Option is Incorrect:**

A. Sacral spinous process is a bony projection located on the dorsal surface of the sacrum, not the ischial spine.
B. The sacral promontory is an area between the sacrum and coccyx, not a structure crossing the ischial spine.
C. The sacrococcygeal ligament connects the ischial spine to the coccyx, not a structure crossing the ischial spine.

**Why the Correct Answer is Right:** The coccygeal arch is the correct answer because it represents the fused coccygeal vertebrae that form a bony arch on the dorsal surface of the ischial spine. This structure is crucial in understanding the anatomy of the pelvic region and the lower back.

**Clinical Pearl:** The ischial spine anatomy is essential for understanding conditions like coccydynia, a type of pain originating from the coccyx. Understanding the correct answer helps in diagnosing and treating such conditions appropriately.

**Correct Answer:** D. Coccygeal arch