The glans, or glans penis, is the technical term for the sensitive head of the penis. It is sometimes also referred to as the "helmet" or the "bell end" of the penis because of its shape. Anatomically, it extends from the corpus spongiosum, which is spongy tissue within the penis that surrounds the urethra. This spongy tissue cushions the urethra during erection of the penis and prevents it from closing. The corpus spongiosum is surrounded by the corpora cavernosa penis, the erectile tissue that fills with blood when the penis is erect. At the tip of these structures lies the glans, which houses the urethral opening.
Uniquely structured, the glans creates a helmet or mushroom shape because of the corona, the raised edge at the back part of the glans, which often also causes the head of the penis to be larger in circumference than the penile shaft. Sensitivity is heightened in this area as well as in the frenulum, which lies just below it. Behind the corona is a sulcus, or depression, between the corona and the penile shaft. Scientists debate the purpose of this "rim," uncertain as to its exact function, though it might exist simply to increase sexual stimulation in both male and female during intercourse rather than providing any distinct evolutionary advantage.
Skin on the outer layers of the head of the penis is made up of mucocutaneous tissue, similar to the skin on the inside of the mouth, which is extremely sensitive. In uncircumcised males, the foreskin of the penis covers the glans when the penis is flaccid, and the skin on the head of the penis remains moist. The foreskin, also known as the prepuce, also is mucocutaneous tissue and attaches to the penis at the frenulum of prepuce of penis. This attachment point is found on the underside of the penis, where the glans meets the shaft, and is visible in circumcised as well as uncircumcised men.
After circumcision, or the removal of the foreskin, the glans is left exposed and becomes dry and less pliant. Some believe this causes the skin of the glans to thicken and become less sensitive. Others feel removal of the foreskin helps maintain better hygiene for young children and has little effect on the sensitivity of the glans. Circumcision is not medically necessary and usually is performed because of personal or religious preference. Debate continues on whether circumcision has a significant effect on sexual stimulation.