In horses, which structure is likely to be affected by a palmar nerve block?

A palmar nerve block primarily targets the nerves that supply the structures in the palmar region of the horse's foot and lower limb. The correct answer pertains to the bulbs of the heel, which are innervated by the palmar nerves. This region includes structures such as the digital cushion and the bulbs themselves, making them sensitive to nerve blocks that affect this area.

In practice, a palmar nerve block is particularly useful in alleviating pain associated with various conditions in the hoof and surrounding tissues, enabling veterinarians to diagnose issues more effectively. By blocking sensation in the bulbs of the heel, the horse may show reduced signs of discomfort when weight-bearing.

The other options represent structures that may not be directly influenced by a palmar nerve block. For instance, the distal interphalangeal joint, P3 (third phalanx), and the navicular bone are typically associated with different nerves or require more comprehensive nerve blocks to achieve anesthesia in those areas. Thus, the focus on the bulbs of the heel aligns with the specific targeting of the palmar nerve block in clinical practice.