Structure and Erection Mechanism of the Male External Genitalia (Pension)
male external genitalia penis
The male genitalia are divided into internal and external genitalia. The internal genitalia include the gonads (testes), ducts (epididymis, vas deferens, ejaculatory ducts, seminal vesicle), and accessory glands (seminal glands, prostate gland, bulbourethral glands). The external genitalia include the penis, foreskin, scrotum, etc.
The penis is the organ for male sexual intercourse, and therefore the most important external genitalia for men.
The penis is a spongy, cylindrical structure, divided into three parts: the glans, the shaft, and the root. The posterior part of the shaft is the root, attached to the pubic arch. The middle part is the shaft, and the swollen anterior portion of the shaft is the glans, which resembles a turtle's head, hence its common name. The glans is richly supplied with nerve endings and is highly sensitive to sexual stimulation. The tip of the glans contains the external urethral orifice. The slightly tapering portion behind the glans is the neck.
The penis consists of two corpora cavernosa and one corpus spongiosum, all covered by fascia and skin. The corpora cavernosa are cylindrical bodies tapering to points at both ends, arranged closely side-by-side on the dorsal side of the penis. Their anterior ends are embedded in the depressions on the underside of the glans penis, while their posterior ends, called the crura, separate and attach to the pubic arch. The corpus spongiosum is also cylindrical, located ventrally on the ventral side of the corpora cavernosa. Its anterior bulge forms the glans penis, and its posterior end, also enlarged and called the bulbourethral corpus, lies between the two crura. The urethra passes through the entire length of the corpus spongiosum.
Both the corpora cavernosa and the corpus spongiosum are composed of numerous trabeculae and cavities. These cavities are filled with blood and connected to blood vessels. When these cavities are filled with blood, the penis becomes thicker and harder, resulting in an erection. The three corpora cavernosa are covered by the penile fascia and skin. The penile skin is thin and soft, with loose, elastic subcutaneous tissue. The skin forms a ring-shaped fold at the neck of the penis, called the foreskin. The opening formed by the free edge of the foreskin is called the foreskin orifice. The fold of skin connecting the foreskin to the external urethral orifice on the midline of the ventral side of the glans penis is called the frenulum. Children's foreskins are generally longer; as they grow older, the foreskin gradually retracts, and the foreskin orifice gradually widens. If an adult's foreskin covers the glans penis but can be retracted to expose the glans, it is called phimosis. If the foreskin orifice is too small and cannot be retracted to expose the glans, it is called paraphimosis.
The length and girth of the penis vary greatly from person to person. Even for the same individual, its size can differ significantly depending on their mental state and environment. It's worth noting that penis length and girth are not necessarily proportional to body size. Some tall individuals may have smaller penises than shorter individuals, which is perfectly normal.
Some young men mistakenly believe their penis is too small and worry that they won't be able to bring their partners pleasure during sex, thus affecting the harmony and satisfaction of their sex life. Others mistakenly believe their penis is too large and worry that they will experience sexual difficulties after marriage, causing their wives pain and harm. In fact, these worries are completely unfounded and unnecessary.
Here, I'd like to introduce a very interesting phenomenon: When the penis is flaccid, the size difference between individuals can be significant, but when the penis is erect, these size differences become very small. In other words, a smaller penis when flaccid grows a larger proportion when erect, while a larger penis grows a smaller proportion. This self-adjustment makes the length of penises of different sizes almost the same when erect, compensating for the original difference. Sexual intercourse takes place in an erect state, and the self-adjustment of the penis after erection successfully compensates for individual differences in body and penis size, allowing most couples to adapt well to each other and achieve maximum pleasure and satisfaction in their sex life.
The penis, as the male sexual organ, becomes erect during sexual arousal. Penile erection is a neural reflex controlled by higher centers in the brain. Various sexual stimuli, such as physical appearance, language, and touch, are transmitted to the cerebral cortex via nerves. After comprehensive analysis, these stimuli arouse sexual desire, exciting the sexual control center and sending nerve signals. These signals are then transmitted to the erectile nerves that control penile erection. When this excitement reaches the penis, numerous small arteries connected to the corpora cavernosa dilate, drastically increasing blood flow. The corpora cavernosa swell with blood, causing the penis to approximately double in size and become erect. After sexual intercourse ends or sexual desire subsides, the penile arteries constrict, reducing blood flow, while small veins open, causing the accumulated blood to drain rapidly. The penis then quickly becomes flaccid.
Penile erection is a manifestation of sexual arousal. However, erections can sometimes occur without sexual stimulation. For example, when there is too much urine in the bladder, a nerve reflex can trigger an erection.