run the length of the penis shaft.
Next comes a key chemical reaction. When arteries dilate anywhere in your body—whether in your cheeks when you blush, your gut when you eat, or your genitals when aroused—they release nitric oxide. b In the penis, this very special molecule (not to be confused with nitrous oxide, your dentist’s laughing gas, or nitrogen dioxide, the air pollutant) signals the smooth muscles to relax even further. More blood rushes in. By this point, the penis is crowded with liquid, and the increased volume compresses nearby veins, blocking their blood from flowing back out again. The chamber becomes tenser and tenser with trapped liquid, assisted by other structures that tighten and constrict. Pressure soars inside the fleshy tube. Most erections reach an internal pressure of one hundred millimeters of mercury—comparable to that which a boa constrictor might use to suffocate its prey.
To protect the organ from rupturing under this intense force, a complex net of collagen fibers surrounds the outside of the penis, under the skin. As Kelly describes, the collagen strands are arranged in deeply folded, alternating perpendicular layers along the length of the penis. This allows them to pleat open efficiently when the erection is under way. Not only does this collagen “skeleton” strengthen the erection, it gives the structure a resistance to bending that engineers call “flexural stiffness.”(Kelly says it’s a trick shared by pufferfish, whose expandable skin also contains highly crimped, alternating strands of collagen.) When the penis is not being used for copulating or mating displays, the erective construction has the added benefit of folding away for neat storage. Being able to stow your penis provides more than simple convenience.A study on certain fish that cannot retract their reproductive organs—because they’re modified, permanently stiffened anal fins—showed that males with longer ones suffered higher rates of predation than those with organs that were less obviously on display.
When the erection is complete, and stimulation has reached what doctors poetically if vaguely describe as the “point of no return,” a spinal cord reflex causes a sudden burst of muscle contractions throughout the genital area, starting with the neck of the bladder. In rippling chains of contractions fueled by massive outflow from the sympathetic nervous system, the muscles around the testes and scrotum tense, followed by those of the epididymis, vas deferens, seminal vesicles, prostate gland, urethra, penis, and anal sphincter. The rapid clamping and unclamping of these muscles, at intervals less than a second apart, spurts semen out of the urethra. A few slower spasms may follow that initial explosion of muscle activity. This sequence has been preserved across a wide spectrum of mammalian species.
The comparative study of ejaculation has focused mostly on primates and rodents.But all male mammals descend from shared ancestral ejaculators. The penises of mammals from narwhals to marmosets to kangaroos propel semen in nearly identical ways.And the ejaculation of a male human today even shares basic physiology with reptiles, amphibians, and sharks and rays. Ejaculation isn’t new. In fact, the human seminal propulsion system has ancient origins. This makes it not only intriguing but plausible that the human male’s experience of ejaculation may be shared by other animals. With the mechanics being so similar, the question is, do other animals experience the intense pleasure that drives so many men to such good and bad behavior?
The experience of orgasm is not only legendary but also measurable.Electroencephalograms show brain-wave shifts, including an increase in slow-frequency theta waves, which are associated with deep relaxation.Many men describe a feeling of euphoria intriguingly similar to what heroin users describe experiencing when they plunge a needle intoa blood vessel and discharge the
Next comes a key chemical reaction. When arteries dilate anywhere in your body—whether in your cheeks when you blush, your gut when you eat, or your genitals when aroused—they release nitric oxide. b In the penis, this very special molecule (not to be confused with nitrous oxide, your dentist’s laughing gas, or nitrogen dioxide, the air pollutant) signals the smooth muscles to relax even further. More blood rushes in. By this point, the penis is crowded with liquid, and the increased volume compresses nearby veins, blocking their blood from flowing back out again. The chamber becomes tenser and tenser with trapped liquid, assisted by other structures that tighten and constrict. Pressure soars inside the fleshy tube. Most erections reach an internal pressure of one hundred millimeters of mercury—comparable to that which a boa constrictor might use to suffocate its prey.
To protect the organ from rupturing under this intense force, a complex net of collagen fibers surrounds the outside of the penis, under the skin. As Kelly describes, the collagen strands are arranged in deeply folded, alternating perpendicular layers along the length of the penis. This allows them to pleat open efficiently when the erection is under way. Not only does this collagen “skeleton” strengthen the erection, it gives the structure a resistance to bending that engineers call “flexural stiffness.”(Kelly says it’s a trick shared by pufferfish, whose expandable skin also contains highly crimped, alternating strands of collagen.) When the penis is not being used for copulating or mating displays, the erective construction has the added benefit of folding away for neat storage. Being able to stow your penis provides more than simple convenience.A study on certain fish that cannot retract their reproductive organs—because they’re modified, permanently stiffened anal fins—showed that males with longer ones suffered higher rates of predation than those with organs that were less obviously on display.
When the erection is complete, and stimulation has reached what doctors poetically if vaguely describe as the “point of no return,” a spinal cord reflex causes a sudden burst of muscle contractions throughout the genital area, starting with the neck of the bladder. In rippling chains of contractions fueled by massive outflow from the sympathetic nervous system, the muscles around the testes and scrotum tense, followed by those of the epididymis, vas deferens, seminal vesicles, prostate gland, urethra, penis, and anal sphincter. The rapid clamping and unclamping of these muscles, at intervals less than a second apart, spurts semen out of the urethra. A few slower spasms may follow that initial explosion of muscle activity. This sequence has been preserved across a wide spectrum of mammalian species.
The comparative study of ejaculation has focused mostly on primates and rodents.But all male mammals descend from shared ancestral ejaculators. The penises of mammals from narwhals to marmosets to kangaroos propel semen in nearly identical ways.And the ejaculation of a male human today even shares basic physiology with reptiles, amphibians, and sharks and rays. Ejaculation isn’t new. In fact, the human seminal propulsion system has ancient origins. This makes it not only intriguing but plausible that the human male’s experience of ejaculation may be shared by other animals. With the mechanics being so similar, the question is, do other animals experience the intense pleasure that drives so many men to such good and bad behavior?
The experience of orgasm is not only legendary but also measurable.Electroencephalograms show brain-wave shifts, including an increase in slow-frequency theta waves, which are associated with deep relaxation.Many men describe a feeling of euphoria intriguingly similar to what heroin users describe experiencing when they plunge a needle intoa blood vessel and discharge the
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