The frenulum (Latin: frenulum preputii; Japanese medical term: 包皮小帯 / 陰茎小帯) is a thin V-shaped fold of tissue connecting the ventral surface of the glans to the inner foreskin. Widely known in Japanese by the colloquial urasuji (“underside ridge”), it is treated as one of the most sensitive regions of the penis.

Anatomical structure

The frenulum arises on the ventral side of the glans, just below and lateral to the urethral opening, running as a slender fold that draws the foreskin downward and connects to the inner preputial lamina. Its length varies between individuals; when short (frenulum breve), the foreskin is pulled excessively taut and can produce pain or bleeding during intercourse.

Histologically the frenular skin is thin, with a shallow dermis and an abundance of fine-touch receptors such as Merkel discs and Meissner corpuscles. This high density of mechanoreceptors is the neuroanatomical basis for the common report that stimulation of the frenulum produces especially strong pleasure. Across the whole penis, the glans, frenulum, and coronal sulcus form the region of highest nerve density, and together they carry the bulk of sexual stimulation.

High-sensitivity erogenous function

For many men the frenulum is among the most sensitive of erogenous zones, responding strongly to even light tongue contact or fingertip friction. The technique of concentrating tongue stimulation on the frenulum during fellatio is known in Japanese as urasuji-zeme and is widely practised as a means of rapidly building toward ejaculation. Because of this sensitivity, stimulation that is too intense or too sudden may register as ticklishness or overstimulation rather than pleasure, so the strength and pace of contact must be adjusted to the individual.

Relation to the foreskin

When the foreskin covers the glans (phimosis), the frenulum is not easily accessible from the outside in the resting state. Circumcision (annular excision) fully exposes the frenulum at the skin surface. Some men report that the frenulum “disappeared” or that sensitivity changed after surgery, but whether the frenulum is itself excised depends on the technique. Some circumcision procedures explicitly advertise frenulum preservation to address patients concerned about postoperative sensitivity.

Injury and tearing risk

Because it is a thin structure, the frenulum is prone to injury (tearing, microfissures). Vigorous friction during intercourse, especially with insufficient lubrication, readily produces fissures. A frenular tear causes sharp pain and minor bleeding; most heal spontaneously, but repeated tearing can lead to scarring and reduced sensitivity. With frenulum breve, the fold is too short for the foreskin to retract fully, producing constant tension and pain. The surgical treatment, frenuloplasty, lengthens or reconstructs the frenulum and resolves the symptoms; it is a short procedure under local anaesthesia with little long-term impact on sexual function.

Care notes

The frenular region concentrates sebaceous (Tyson’s) glands, and in unclean conditions smegma accumulates readily, so hygiene is the basis of preventing frenular problems. Minor abrasions after intercourse are not rare, and the area can become an entry route for infection, including sexually transmitted infections, which warrants attention.

Related terms

• Penis
• Foreskin
• Phimosis
• Erection