Anatomy of the penis

There are two types of erectile tissue in the penis, namely the corpora cavernosa and the corpus spongiosum. During sexual arousal, blood fills these spaces (it's analogous to a Reebok pump shoe) and causes erection.

The cone-shaped glans penis at the distal end of the penis is an extension of the corpus spongiosum. The glans penis is covered by a loose fold of skin called the prepuce or foreskin. Circumcision is the surgical removal of the foreskin, usually done for religious reasons.

penis: the male urinary and copulatory organ, comprising a root, shaft, and at the extremity, glans penis and foreskin [from Latin, penis, or tail]. The shaft or body of the penis consists of two parallel cylindrical bodies, the corpora cavernosa, and beneath them, surrounding the urethra, the corpus spongiosum. The penis in the male is the homologue of the clitoris in the female.

Dictionary of Sexology Project: Main Index

PENIS is an acronym for Proton Enhanced Nuclear Induction Spectroscopy.

In layman's terms this is a method of determining which light wavelengths a given substance will absorb, or what wavelengths it emits. This is useful in determining the exact makeup of a substance.

The story behind this acronym is that the editors of a scientific journal back in the 1970s did not like a certain scientists idea on something or another (rejecting his paper). So a few months later he submitted a wonderful paper on Proton Enhanced Nuclear Induction Spectroscopy, and he referred to it by its acronym PENIS throughout the entire paper (they still published it). The article appeared in the Journal of Magnetic Resonance (probably not a lot of subscribers to that one), in 1974, and was written by T Merrick.

What's it like to have a penis?

This question was posed in another node, so I shall do my objective best to answer it. Keep in mind, as it was rightly pointed out in the originating writeup, that having had a penis all my life makes this kinda difficult to be 100% objective, but I shall certainly do my best to try.

One of the first things that should be made clear about having a penis is that it can be a very annoying thing sometimes. Peeing with an erection, shifting, sweating, sensitivity, itching... that whole jock itch thing is not the big joke people might expect. Imagine your foot itching really, really bad, but not being able to publicly scratch it for fear of offending someone's societal mores- or your own. I mean, blatantly itching one's member is not exactly something that can be done in the open without someone noticing. Men, if they're smart, learn over the years how to be as surreptitious about this activity as possible because, while women are loathe to wave their soiled panties in the air, men are just as reluctant to have everyone and their dog know that jock itch is an "issue" at any given moment. Another thing about jock itch is that it is not permanent. The best way to avoid it, as with any other kind of itching, is to keep one's undershorts clean as well as the affected area.

I'm sure that many women have made the mistake of thinking that it is the penis which lends many men a certain measure of empowerment. This is a falsehood; it's not the penis itself which empowers us, but it is the idea of it. It is a visual affirmation of our maleness (aside from angular physiological geometries and muscular definition), it is the thing which gives life to the womb and it is often a status symbol (if size isn't an issue to women, it most certainly is to most men, whether they admit it or not). Yes, penis envy exists just as much as breast envy. But, as with women's breasts, there are limits to the matter of jealousy. A man whose member is significatly larger than "necessary" is not as lucky as you would think. For starters, any women such an individual encounters sexually are hopefully endowed with patience, endurance and perhaps just a little humor. Any man who is actually interested in making a woman feel physically uncomfortable while having sex, due solely to the size of his penis, is missing the whole point of sex, isn't he? I mean, sex is supposed to feel good for both (or more) parties involved. And therein lies the greatest reason men feel empowered by their penises... used properly, a penis can be capable of inspiring massive amounts of pleasure in one area while the hands are free to pleasure other areas as well. At the base level, men more often than not feel empowered by their penises because of the convenience it offers them during sex. Plus, there's the whole writing-your-name-in-the-snow thing, which is a feat I have yet to hear a woman claim. When I meet a woman who can reliably prove to me that she can write her name in the snow while urinating, I will stand up, walk out of the room and demand a refund on that thing between my legs.

Heft: do not discount the feeling of it or the sense of awareness it can inspire in a man. When a man stands up and feels his cock shift slightly in one direction or another, he is suddenly and acutely aware of the fact that is, indeed, male. Don't be fooled- regardless of a man's intellect, I would swear that we sometimes forget our genders. Actually feeling that thing down there moving as it is wont to do is a gentle reminder and, sometimes, it can be quiet pleasurable. Remember: the male genital area is extremely sensitive. The slightest sensation can be felt like a thunderclap, under the right circumstances.

There is a supposed fact that men think of sex an average of every seven seconds. Women's genitalia are concealed and secreted away; a man's is not. Because of this protrusion at our groins, which is sensitive and reactionary, is it any wonder that we think of sex so often with such an insistent reminder? I am sure that there are many groups out there who would have you mentally associate the "natural" male tendency towards aggression and sex, but the simple fact of the matter is that we think of sex so often because we can't really hide our sexual organs except by cosmetic or fabicated means (by this I mean clothing). Believe me, it can be very distracting. I have, on countless occasions, been involved in engrossing conversations with members of the female half of our species and felt at a crossroads simply because something down there twitched unexpectedly- and the twitching wasn't necessarily inspired by her. It often was caused by crossing or uncrossing my legs, walking, being bumped... in short, physical stimulation that had absolutely nothing to do with her, but caused a physical and mental response which resulted in carnal thoughts- if only briefly.

A penis, like anything else on a human body, is like a snowflake: no two are exactly alike. This is a truism that I'm sure goes without saying except that it is a setup for a very important issue: appearances can be deceiving. What I mean is, the way a man looks has almost nothing to do with the shape of his penis. That old yarn about a man's hands and feet or his nose having a direct correlation with the size of his penis is utter nonsense, a myth. The surest way to find out what a man's size/girth is like is to, well, see for yourself and stop trying to second-guess genetics. And that is what is at the heart of the matter, where size is concerned. As with everything else in life, that wonderful gambling game we call genetics makes it a crap-shoot. A man's size is based purely on luck (or not, depending on your perspective). His hands have nothing to do with it, nor do his feet or his nose. Furthermore, it is extremely unlikely that a man can improve the size of his penis through mechanical means, barring cosmetic surgery. This means that giving your husband/boyfriend a penis enlargement system (pump) is about as pointless as him sending away to Mazatlan for the oft-fabled Spanish Fly- both are moot and can actually cause more harm than good. Even cosmetic surgery, as with any sort of "elective" surgery, has its pitfalls and should be considered with the utmost care. After all, it's not the size of the sword.....

Here's an interesting issue: to nip the tip or not? What purpose does the hood of a man's uncircumcised penis have? Well, to be perfectly blunt, none in this day and age, but it's nature is to keep the penis' only opening protected from various forms of bateria and general foreign matter. In many ways, the "excess" skin on an uncircumcise penis has the exact same function as the hood which covers the clitoris on a woman's genitalia. What does this mean, exactly? Nothing much except that a man who has not been modified (as such) will have to make certain that he keeps the head of his penis clean. This involves (usually) gently pulling the skin away from the glans (head) and washing with soapy water. For a man who has been circumcised, he has nothing to really worry about as far as cleanliness is concerned- as long as he bathes regularly. The reason circumcision was instituted, far back in the past (far longer than I can probably count, though a Jew might be able to shed more practical light on when it was started), had everything to do with cleanliness and general health. At the time, humankind hadn't developed running water and plumbing systems. Baths, when they could be taken, were generally had at public bath houses or in rivers/creek beds. I don't know if you've given it much thought, but both such places can tend to be very unsanitary locales. Men were dying in large numbers from gonorrhoea and syphilis, and probably early forms of hepatitis as well, and it was deduced that many of these men had been infected while bathing. The excess skin of the male penis would inadvertantly retain certain microbes, which could find their way into the ureter and thereby infect with fantastic ease. Someone eventually realized that it was possible to "snip" off this bit of skin and make it easier for men to keep their genitals clean and, hopefully, avoid infection. Over time this very practical and medically sound concept managed to get some pseudo-religious traditions attached to it and then having your son's bris became all the rage. Fact is, due to our advancements in personal hygiene, circumcision is not exactly necessary, but it is some minor convenience- one less thing (pun intended) to pay extra attention to when showering. Can a man get circumcised later in life? Certainly, though it hurts like a four-alarm bitch and the healing process takes longer, but it doesn't diminish a man's sexual prowess any- nor does doing so improve it.

I won't go into describing the actual sensation of an orgasm or even urination- I leave that to more prolific, if more risqué, writers. Since I have never been a woman, I find it difficult, at best, to even form a comparison or simile. All I can say on the topic is that it feels really damn good to have an orgasm and, sometimes, just as good to take a piss- I don't know exactly why this is, but I suspect it has something to do with all of our sexual nerve endings being located in the same exact place where both fluids exit our bodies. Hrm... perhaps I can give the whole why-does-urinating-feel-good-to-a-man question an interesting corrollary.... From what I hear, women enjoy feeling warm, wet kisses on their clitorises, yes? I'm sure most if not all of you women have experienced the sensation of having warm water trickle over the clitoris while showering. Question: did it feel really damn good? If so, that's probably a close approximation to what a man feels when he's urinating, only times ten because the fluid is 1) body-temp and 2) prolonged. Beyond that, I'm at a loss for words to describe it. An orgasm is right up there with trying to describe snow to a man who has never seen it and likely never will: impossible to convey with words.

If anyone else has some reliable anecdote for what it's like to have a penis (a practical anecdote!), then please don't hesitate to contribute. Like I said earlier, they're like snowflakes: no two are exactly alike. One man's perspective could be drastically different from another's. I hope this was informative enough to allow the female members of our species at least a glimpse into what it's like to have one of these things. Sometimes its an inconvenience, but it's also pretty damn interesting and even, yes, fun. After all, sometimes they're fun to point at and giggle- perhaps even laugh out loud at the strange, cylindrical thing dangling between our legs. That they can cause so much trouble and still prove useful is nothing short of amazing to me, but there ya go.

The penis is an organ of the male reproductive system, serving to deposit sperm into the female body, enabling internal fertilization. Of course, this is essentially the definition of any intromittent organ, and it is not universally agreed which intromittent organs should be called penises – I tend to limit the term to the organs of amniotes, in which the development of organs capable of internal fertilization was an important step in vertebrate development, enabling reproduction outside of a water environment. Ultimately, this is a somewhat anthropocentric definition, encompassing those organs most similar in structure and origin to the human penis, but it will have to do for now. Even with this limited definition, there is significant variation in penis structure and appearance between species, from the familiar and relatively straightforward human penis to the corkscrew penis of ducks and pigs to the dual hemipene of reptiles and the similar structures of marsupials.

At its most basic, the penis is a tube of some length, made rigid by bone, blood, or some combination of the two, which places sperm inside the female, where it fertilizes eggs which are then laid or gestated inside the female. In most mammals, like humans, the penis places sperm in the vagina, which then migrates to the uterus to fertilize eggs. However, in some mammals, like horses, sperm is deposited directly into the uterus, which partially accounts for the reputed length of that species’ penises. Some species’ penises go further than this and perform additional functions to encourage reproduction. The penis and sexual practices of humans and other primates (ideally) stimulate the vagina and clitoris and induce orgasm in the female, which creates muscular contractions and repositions the cervix, both of which appear to make it more likely for sperm to enter the uterus, and from there, fertilize an egg. Looking at two other animals familiar to humans, the male cat has a barbed penis which rakes the vagina during withdrawal, a process that is believed to help incite ovulation, and a section of the canine penis, the bulbus glandis, near the base, swells while in the vagina and prevents full disengagement for up to an hour after ejaculation, ensuring completion of coitus, sealing the male dog’s semen inside the bitch, and preventing her from mating with competitors, at least for a while.

The Human Penis

The external appearance of the penis is that of a fleshy tube emerging from the crotch near the bottom of the pubis and forward of the testicles. When flaccid, the penis usually hangs downwards, although being bound in underwear or clothes may place it in another position. When erect, the penis grows larger in width and girth, becoming closer to horizontal to the body, though some penises may tend to lean or curve upwards or to one side.

The skin on the shaft of the penis is softer than surrounding skin and may be slightly different in coloration. As the skin on the shaft must accommodate the penis' full erect size, when flaccid or semiflaccid it may seem wrinkly or loose. The veins running under the surface of the shaft are sometimes visible and/or prominent, varying with the individual. The shaft contains a higher density of nerve endings than normal skin and is accordingly more sensitive, and stimulation of the shaft may cause erection, which will be discussed later. At the end of the penis is the glans, or "head", which is made of a different kind of tissue from the majority of the shaft, with an exterior that is differently textured and has an even higher nerve density and thus sensitivity. The glans is often said to look like a helmet, at its longest on the top of the penis and curving around on either side to its shortest on the underside. At the tip of the glans is the meatus, a small hole which is the external opening of the urethra; this is where urine and semen are expelled from the penis. When flaccid, the glans is covered to some degree by the foreskin, an extension of the skin that covers the shaft but, again, with higher nerve density, considered to be almost as sensitive or more so than the glans. The foreskin can be drawn back to expose the glans, and when erect, the glans emerges from the foreskin. It is a regular practice among some cultures to surgically remove the foreskin, often shortly after birth; this procedure is called circumcision.

In most embryos with XY chromosomes, the glans develops out of the genital tubercle and the shaft from the genital folds around the 8th week of gestation, in response to male hormones produced by the embryonic testes. In females, these structures would instead go on to become the clitoris and the labia minora, respectively. Average penis length at date of birth is around 1.15 to 1.75 inches, and genetically male or nonstandard babies with penises of less than .6 inches in length and .3 in width are often declared female on birth certificates. The penis grows larger with age, most dramatically during puberty, and by adulthood, though the results of individual reports vary, the average penis length appears to be about 6.1 inches when erect. Flaccid length shows more variation and little correspondence to erect length, but seems to average around 3.9 inches.

When you get down to it, there are more or less three things of note that the penis does - erection, ejaculation, and urination.

Erection can be brought on by a variety of causes, mental and physical, voluntary and involuntary, the most obvious of which is stimulation of the penis. The bulk of the shaft of the penis consists of the corpus cavernosa, two side-by-side cylinders of spongy tissue. When erection occurs, the blood vessels feeding the corpus cavernosa dilate, allowing more blood into the penis, flooding into the corpus cavernosa and filling the holes in the tissue, known as "sinuses". The veins which would drain blood from the penis simultaneously constrict and are pressed against by the swelling corpus cavernosa, decreasing the rate at which blood leaves and trapping it in the penis. As the penis fills with blood, it expands, first in length and then in girth, and the pressure of the blood within makes it stiff.

Ejaculation under normal conditions takes place as part of orgasm, which in turn is usually caused by stimulation of the penis, meaning that the penis is typically erect for ejaculation. Much of ejaculation takes place "upstream" of the penis, with sperm produced by the testes, seminal fluid from the seminal ducts and vesicles and prostatic fluid from the prostate mixed together and propelled onward by contractions of the genital tracts. The penis does its part, along with the perineum, by rhythmically contracting the smooth muscle along the penile urethra, which runs through the penis along the underside, projecting the semen out of the meatus. The initial few contractions occur at roughly .8 second intervals, but later contractions occur at longer intervals and with less force. Depending on the man, ejaculate may be initially be propelled with enough force to travel several feet, or may exit the penis with a relatively low velocity. After ejaculation the blood in the penis begins to drain and the penis shrinks, and the man enters the refractory period, in which erection is difficult and orgasm impossible.

As with all mammals, male humans urinate through the penis. The walls of the bladder contract and the sphincter surrounding the urethra relaxes, forcing urine through the urethra and out of the body through the meatus. Because of the positioning and anatomy of the penis, a male's urine stream while standing will project outwards from the body, and men may use their hands to aim their penises and direct the flow. During urination, sphincters inside the body contract to close off the connection between the reproductive tract and the urethra to prevent urine from traveling in the wrong direction or being mixed with ejaculatory fluids; likewise the connection to the bladder is sealed off during ejaculation.

Pe"nis (?), n. [L.] Anat.

The male member, or organ of generation.


© Webster 1913.

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