The foreskin serves three functions: 1. Protective 2. Sensory 3. Sexual
In most cases, the foreskin is stilled fused to the gland penis at birth and will gradually seperate from the gland penis over a variable period of time over the first few years. During the diaper period, the foreskin help to protect gland penis from abrasion with diaper and prevent from contamination with feces. After that period, foreskin keeps the gland penis soft and moist and protects it from trauma and injury.
Inner foreskin and frenulum is pink color part in picture diagram are particularly sensitive and contribute to sexual pleasure. Rich of nerve ending there enhance sexual pleasure and control.
Inner foreskin is mucosa, like the lining of the mouth, which is thinner and different texture and color than skin that cover penile shaft. Frenulum is a particularly sensitive narrow membrane that runs down the ventral groove of the glands and attaches to the inner foreskin.
The ridge band is the interface between inner foreskin or mucosa and the shaft skin. It often “puckers” pass foreword tip of the glands. The band contains smooth muscle fibers, which have elactic property that allow foreskin to be retracted. The ridged band is sensitivity equivalent to that of the lips.
Foreskin provides ample loose skin for the penis to occupy when erect. It is a movable skin sheath for the penis during intercourse, reducing friction and reducing need to use artificial lubricants, and allowing the gland and foreskin to naturally stimulate each other. Warren and Bigelow described some of the physiological functions of the foreskin in sexual activity in British Journal of Sexual Medicine, Sept/Oct 1994.