The structure which passes superficial to the flexor retinaculum
Structures passing over the flexor retinaculum: 

Ulnar nerve and vessels through the Guyon's canal (volar carpal ligament).
Palmar cutaneous branch of ulnar nerve (supply skin over hypothenar muscles).
Palmaris Longus.
Palmar cutaneous branch of median nerve (supply skin over the thenar muscles).
Superficial palmar branch of the radial artery.
Median nerve
Flexor digitorum superficialis
Ulnar nerve
Flexor digitorum profundus