Male and female genitals grow from the same embryonic bud
Every human embryo, male or female, starts with the same small outgrowth called the genital tubercle. Male hormones steer it into a penis, and its tip becomes the glans, which is why the glans is the anatomical counterpart of the clitoral glans. Even its name comes from the Latin for acorn.
The glans is the rounded end of the human penis. Internally it is the enlarged cap of the corpus spongiosum, the spongy tissue that surrounds the urethra and keeps it open as a channel, and it sits over the tips of the two larger erectile columns, the corpora cavernosa. On the outside it is lined with mucosal tissue over a dense connective layer, giving it a smooth, glossy surface. In uncircumcised men it is partly or fully covered by the foreskin, which in adults can usually be pulled back.
Several landmarks define it. At the top is a vertical slit, the urinary meatus, through which urine and other fluids leave the body. The rim around its base, the corona, overhangs a groove called the coronal sulcus, behind which the neck of the penis leads to the shaft. On the underside the two sides of the glans meet along a midline septum, and a flexible, well-supplied band called the frenulum links the foreskin to the head, letting it slide back and return.
Its shape and size vary between men. Commonly acorn-like, it can be broader than the shaft, giving a mushroom profile, or narrower and more probe-shaped. During erection increased blood flow enlarges it, yet it stays softer than the rigid shaft, and that cushioning may help absorb impact. Across mammals the glans takes many forms: smooth in some species, spiny, elongated or even split in others.
Why the human glans has its particular form is unresolved. One proposal holds that its ridged shape evolved to displace a rival's semen during mating. That idea sits awkwardly with the mating behaviour of our primate relatives, and the reason remains uncertain. In everyday speech it is simply called the head or tip.
Source: Glans penis
