Which BL point lies at the level of the lower border of the spinous process of the fourth thoracic vertebra (T4)?

• A. BL 43
• B. BL 41
• C. BL 42
• D. BL 44

Answer: (A)

The Bladder channel on the back follows the spine with points tied to thoracic vertebral levels. The point positioned at the lower border of the spinous process of a given vertebra sits at that vertebral level. In this region, the bladder point located at the level of the lower border of the spinous process of the fourth thoracic vertebra corresponds to the point known as BL 43. So, BL 43 sits at T4, about 0.5–1 cun lateral to the midline on the back.

This is why it’s the best answer: it aligns exactly with the T4 level. The nearby points lie at neighboring levels (slightly above or below), so they would not be at the lower border of T4.