What structures pass deep to the extensor retinaculum?

The correct answer highlights that the extensor tendons and the abductor pollicis longus pass deep to the extensor retinaculum. The extensor retinaculum is a fibrous band located on the posterior aspect of the wrist. Its primary function is to hold the extensor tendons in place as they cross the wrist joint, preventing bowstringing during wrist movements.

The extensor tendons responsible for extending the fingers and the thumb, along with the abductor pollicis longus, which specifically assists in thumb abduction, travel beneath this retinaculum. This arrangement allows for efficient movement and stabilization of the wrist and hand during activities that require extension and abduction.

Understanding the anatomy and function of these structures in relation to the retinaculum is crucial for comprehending both normal wrist function and potential clinical issues that can arise, such as tenosynovitis or other tendon-related pathologies in the wrist.