In-depth analysis of the mysteries of male sexual development and function: A scientific guide from puberty to orgasm

The Mysteries of Sexuality

1. Sexual Development

Normal male development is divided into five stages. Stage 1, 5-9 years old: Testes are small, less than 2.5 cm in diameter; penis and scrotum are infantile; secondary sexual characteristics are not obvious. Stage 2, 9-11 years old: Testes enlarge to 2.5-3.2 cm; penis enlarges; short, fine, light-colored pubic hair grows at the base of the penis and pubic area; scrotal skin is thin and reddish. Stage 3, 11-14 years old: Testes enlarge to over 3.3-4 cm; height increases dramatically; penis enlarges significantly, first in length, then in thickness; scrotum enlarges; by age 12, height, weight, and shoulder width reach their peak; pelvis and chest circumference increase; pubic hair becomes thicker, longer, stiffer, and darker. The fourth stage, from 14 to 16 years old, involves the testes increasing in diameter to 4.1-4.5 cm, the penis becoming larger and thicker, the scrotum enlarging and darkening in color, the first nocturnal emission occurring, lasting 3-4 years, pubic hair becoming more widespread, extending to the groin and upper pubic bone, the Adam's apple enlarging, the voice deepening, and the beginning of axillary hair growth. The fifth stage, after 17 years old, involves the testes, scrotum, and penis resembling those of an adult, approaching maturity, with pubic hair exhibiting a male-dominated diamond shape, and muscle and bone development becoming robust, resulting in a strong male physique.

2. Libido

Libido has two aspects: First, it refers to the desire to obtain physical and mental pleasure through conscious or unconscious sexual activity, a combination of love and lust, a unity of spirit and flesh; second, it refers to the desire to engage in sexual intercourse. Sexual desire is sexual arousal initiated by stimulation at a specific time, place, and with a specific object. When sexual desire reaches a certain level, it can cause penile erection or vaginal lubrication; it is a human instinct. Once sexual maturity is reached (around 13 years old on average in modern times), an urgent need for sexual satisfaction arises. Suppressing this desire leads to anxiety, tension, and boredom; while satisfying sexual desire brings pleasure and relaxation. Sexual desire is divided into two types: the desire for contact and the desire for ejaculation. The desire for contact refers to the desire for skin-to-skin contact between men and women. Sexually mature men and women touch each other's sensitive areas to achieve sexual satisfaction. The desire for ejaculation refers to the male's desire to obtain sexual pleasure through ejaculation. A man's semen is normally stored in the seminal vesicles. When intercourse is about to reach orgasm, the seminal vesicles reflexively contract, ejaculating the semen out of the body, thus fully releasing sexual energy and obtaining sexual pleasure. Sexual desire is usually aroused by sensory stimulation. Men are aroused by visual stimuli such as female breasts, sex films, and erotic literature; while women are more easily aroused by tactile stimulation, such as touching erogenous zones. Sexual desire is the prelude to sexual function or behavior; normal sexual function requires the initiation and maintenance of sexual desire. Everyone's sexual desire varies greatly, and even within the same person, the strength of sexual desire can differ.

3. Sexual Impulse

Sexual impulse is the human desire or impulse for sexual behavior. The generation of sexual impulse requires motivation. The motivation for human sexual impulse comes from three sources: instinct, hormones, and sexual release factors. Instinct refers to the natural ability of animals to preserve themselves and their species. Sexual behavior is a primary way to preserve the species. Although it is an instinct, in humans, it is also controlled by the limbic system and hypothalamus of the brain. The limbic system controls sexual behavior. The limbic system is connected to the brain and adjacent to the hypothalamus. The transmission of sexual impulses and the issuance of sexual commands are both directed, coordinated, and communicated by the limbic system. For example, when the brain generates sexual desire, it transmits this information to the hypothalamus and limbic system, which then instruct the external genitalia via the spinal cord, causing changes in the external genitalia. If sexual activity occurs at this time, the stimulation from the sexual activity is transmitted to the brain, resulting in pleasure. If the brain deems the sexual impulse inappropriate at its onset, it can directly inhibit the limbic system and hypothalamus, thus suppressing the sexual impulse. This fully demonstrates that reason, education, and civilization can completely control immoral sexual behavior. Most forms of sexual impulse depend on gonadal activity, including the exocrine (sperm, egg) and endocrine (hormones, etc.) secretions of the gonads. The gonads refer to the testes and ovaries. The male gonads (testes) function to develop boys into typical men. Therefore, we can say that sexual impulse originates entirely from the testes and ovaries. For humans, among the various factors driving sexual motivation, the brain plays a commanding role. Influenced by reason, experience, and culture, the brain should be able to control sexual impulses, ensuring that sexual behavior conforms to civilized, legal, and moral norms.

4. Sexual Function

Sexual function includes three aspects: reproductive function, sexual behavior function, and sexual sensation function. Healthy sexual function refers to a state of good physiological activity, psychological and behavioral responses, and social adaptability related to sex. This good state not only brings pleasure to the individual but also brings peace to social life. American medical psychologist Levin believed that normal sexual function should mean that during intercourse, the nervous systems of both men and women can smoothly and harmoniously complete each stage of sexual response, and that their mental activity can focus on the completion of sexual behavior without any other thoughts. Normal male sexual function includes processes such as sexual arousal, penile erection, intercourse, ejaculation, and de-excitement. The process of female sexual activity is not as obviously varied as that of male sexual activity. When stimulation is received by the erogenous zones, it reaches the sexual center in the cerebral cortex via nerves, stimulating excitement. This excitement is then transmitted downwards through nerves to the sexual center in the spinal cord, gradually entering the excitement phase. This is manifested as: breast and external genitalia becoming engorged and enlarged; increased vaginal secretions, lubricating the vagina and vulva; the lower third of the vagina narrowing due to engorgement, "gripping" the penis; and when sexual stimulation accumulates to a certain level, the muscles of the vagina, perineum, and anus rhythmically contract, reaching a pleasurable climax, which then gradually subsides.

5. Orgasm

An orgasm is an extremely comfortable and pleasurable feeling that occurs after sexual arousal and duration have reached a certain level, resulting from the sufficient accumulation of sexual stimulation. It lasts only a few seconds to a dozen seconds. This feeling is a sign of the fulfillment of sexual desire; only those who frequently experience orgasm can maintain sexual desire. Before orgasm, the man's penis thrusts rapidly inside the vagina, the vagina "gripping" the penis, stimulating it. Afterwards, the man experiences a premonition of ejaculation, which then occurs. At this time, the ejaculatory ducts, seminal vesicles, prostate, and urethral muscles contract rhythmically, causing semen to first collect in the posterior urethra. Then, the prostate, perineal muscles, and penile shaft contract rhythmically together, ejecting the semen from the urethra. Each ejaculation consists of 7-8 spurts, with the first 3-4 spurts containing a higher sperm count, and the latter 3-4 spurts containing a lower sperm count. Ejaculation lasts only a few seconds, but it is a process beyond the man's control. During ejaculation, the man experiences pleasure from stimulation of the glans penis and a sense of psychological comfort and satisfaction. At this point, the man's physiological and psychological euphoria reaches its peak, and he achieves sexual release and satisfaction.

Male orgasm is a fundamental human need, as it is generally accompanied by ejaculation. Only through sperm release can an egg be infused with life-giving energy. During orgasm, men experience a profoundly pleasurable moment, both physically and mentally. Throughout history, people have used poetic language such as "exquisite," "beautiful," "ecstatic," and "indescribable" to express this "supersensory" experience. In contrast, female orgasm is more complex. Scientific tests have shown that both men and women exhibit theta brainwaves with a frequency of 6-7 Hz during orgasm. In men, these waves are extremely brief, occurring only at the moment of ejaculation, while in women, they are present for a longer period. Although the physiological mechanisms of orgasm are not yet fully understood, experts believe that while the outward manifestations of orgasm are strong muscle contractions and a feeling of comfort in the sexual organs and throughout the body, the essence of the entire response may lie deep within the brain—a cerebral experience, a psychological phenomenon related to physiology.

The causes are complex, including biological factors, psychological developmental disorders, and sociological reasons.