Frenulum.

Frenulum.
Occasionally, a persistent frenulum and retention of the attachment between visceral and parietal layers of the inner lamina of the prepuce occurs. The frenulum is a band of tissue that extends from the ventral tip of the glans penis to the prepuce. Separation of the penis from the sheath normally begins at 1 month of age in the bull, and ends with complete separation by 8 months. When the frenulum persists there is usually a blood vessel present in the center of the tissue band comprising the frenulum. Persistence of the frenulum causes curvature of the extended penis.

Larsen RE (2001)