Having said that, if you can get an erection, masturbate and ejaculate, enjoy sex and urinate normally, and you have no infections, phimosis or other problems, then you really don’t have anything to worry about.
Basic anatomy of the uncircumcised penis
Your penis is basically a very specialized roll of flesh with a hollow tube down the middle. This tube, the urethra, is the passage to the outside world for urine and semen. It normally opens as either a small round hole or a long narrow slit on the tip of the glans, although some men have a condition called hypospadias, where the urethra opens somewhere on the underneath of the penile shaft. Often there are two little lips surrounding the end of the urethra on the glans. These lips are full of nerve endings which can provide immense excitement during sexual play.
The glans is the most sensitive part of the penis, as you’d expect, since it leads the way into the vagina during sexual intercourse. Both the coronal ridge of the glans and the frenulum seem to be important in stimulating ejaculation during intercourse.
The frenulum is one of the most sensitive spots on the entire penis, but it is often cut away during circumcision. And Hugh Young, of Intactivism, points out that the foreskin, also removed during circumcision, may actually be more pleasure-sensitive than the glans.
If you want to see some of the unfortunate (and not uncommon) harmful consequences of circumcision, check out the photos here.
Inside the penile shaft, the urethra is surrounded by spongy tissue called the corpus spongiosum. During sexual arousal, a network of small arteries fills the corpus spongiosum with blood. This blood cannot escape because the veins near the base of the penis are constricted by the swelling of the spongy tissue of the corpus spongiosum. In the diagram above you can see that there are two other channels of spongy tissue in the penile shaft, each known as a corpus cavernosum, and these also fill with blood during an erection. As the amount and pressure of blood in the penis increases, an erection begins to develop. If sexual arousal continues, the continuing constriction of the veins traps more blood inside the penis and the erection proceeds to full firmness.
If the penile arteries become blocked by fatty deposits or the veins leak, a man is likely to develop impotence or erectile dysfunction - which means he cannot get an erection or maintain one.
Unfortunately, as a man ages, the blood supply to his penis can decrease because of the increased amounts of fat which are deposited in his penile arteries - and it doesn’t take much to block them, for they are very small in diameter. Such reduced blood flow slowly causes the muscle fibers inside the penis, whose job is to regulate blood flowing through the blood vessels, to degenerate into connective tissue. The greater the amount of connective tissue, the greater the difficulty getting an erection - eventually it will be impossible to get an erection at all. There can also be an apparent reduction in penis size as a man gets older - partly due to this change in tissue structure, and partly due to the amount of fat around his abdomen increasing, so that the base of his penis shaft is less obvious and its apparent size becomes shorter.
Even in a penis with clear arteries, it seems that normal blood flow may not be sufficient to keep the internal tissues healthy, and some doctors have suggested that the function of spontaneous erections during sleep is to ensure good oxygenation of the penis through increased blood flow. In short, it seems that the more erections you have, the healthier your penis will be! It certainly seems logical to me that regular erections are both natural and necessary for ensuring optimum health and maximum size.
The penis goes deep back inside the body, with its “root” reaching back underneath the prostate gland towards the anus. This hidden penile tissue is very sensitive, and stimulating it during sex with fingertip pressure applied either through the scrotum or on the perineum (the area between scrotum and anus) can be very pleasurable.
A lot of men have a penis which shows little or no shaft outside their body when they are not sexually aroused, and it is this hidden part of the penis which can generate a sizeable erection when they become sexually aroused. This is described in greater detail on the size page of this website.
You may have noticed a line along the underside of your penis. This is the “raphe”. As you developed in your mother’s uterus, your penis formed as a tube of flesh which gradually sealed along its length. Normally, the only sign of this process after birth is this thin ridge of skin along the underside of the penis.
The skin of the penis contains muscle fibers which extend from the muscles of the scrotum. These muscle fibres control whether you have a scrotum which hangs loosely, or one which is held tighter against your body. The more active the muscle, the tighter and more crinkly your scrotum appears. Of course, cold water and fear can also cause the muscles to contract, and, as you know, your penis and scrotum will then shrink and appear much smaller.
The length of the foreskin is highly variable, so that in some men there is only partial coverage of the glans, even when the penis is flaccid.
As we said before, the frenulum is one of the most sensitive parts of the penis, but it is often removed during circumcision, along with the foreskin. There’s a picture below of what the frenulum looks like on an uncircumcised man with his foreskin retracted. The foreskin is tethered to the shaft of the penis by the frenulum, which stops it retracting too far and causes it to move forward again after it has been pulled backwards.
The outer surface of the foreskin is skin, but the inner surface is a sensitive mucous membrane that contains sebaceous glands which lubricate and protect the glans from friction. Because circumcision removes these lubricating glands, many circumcised men complain that their glans tissue is too sensitive as it rubs against their clothing. Generally, the foreskin is much larger than you might think - it can be up to ninety square centimeters in area in an adult man. Considering how many more nerve cells the foreskin has compared to the glans, one might guess that circumcision destroys a great deal of a man’s sexual sensitivity.
Finally, the ridged bands on the inner surface of the foreskin near the tip merge with the frenulum and have the highest number of nerve endings of any part of the foreskin. These nerve endings are of a type sensitive to changes in pressure and tension, and are thought to play a part in stimulating and controlling orgasm and ejaculation during intercourse.
One interesting question is whether or not hypospadias can have an impact on sexual functioning. This is a condition where the foreskin may be incompletely formed, leaving a hooded appearance with an incomplete circumference of the foreskin around the glans. The frenulum is usually missing - which may or may not affect a man’s sexual pleasure - but the question for most men is really one of appearance and sexual functioning. I have only come across one man with hypospadias who reported that he had delayed ejaculation. After using a treatment for retarded ejaculation he reported that his sexual function was normal - he ejaculated within five minutes - after previously not being able to ejaculate at all. I assume this was caused buy the psychological impact of the hypospadias and increased confidence resulting from treatment.
The process of erection
How the foreskin works
www.the-penis.com/anatomy-circumcision.html
The erectile mechanism of the penis
Summary of Normal Male Erectile Function
A normal erection is the result of a rather complex process. The penis has three separate tubes that become engorged with arterial blood during arousal. Erotic fantasies or sensory inputs such as the touch, scent, sound or sight of a partner are channeled into the control center in the brain. The aroused brain sends signals down the spinal column to the penile nerves (which may also be stimulated directly by manual stimulation - masturbation, fellatio, or intercourse). The nerve impulses trigger an event involving muscle tissue and blood vessels in the two large erectile cylinders, the corpora cavernosa (singular: corpus cavernosa).There are arteries and spaces called sinusoids within these cylinders, and smooth muscle tissue surrounds the arteries and spaces. Normally, the smooth muscle tissue keeps both arteries and spaces constricted, but the nerve impulses send a primary messenger called nitric oxide (NO). This molecule tells the smooth muscle tissue to relax, which allows more arterial blood to flow into the penis and the capacity of the penis to dramatically increase in volume. Meanwhile, veins that normally drain blood from the penis are flattened by the expanding volume of blood into the erection chambers. The arterial blood is thus trapped, making the penis very hard and very erect. Continued stimulation keeps the process going and maintains the erection.
Now, here is a more complex description:
Anatomy of the Penis
The penis is composed of three erectile cylinders. A pair of spongy cylinders (the corpora cavernosa) are located side-by-side on top. They join in the midline for about 70 pecent of their length - that part of the penis that extends from the body - and continue separately behind the pubic bone where they are anchored to the underside of the pelvic bony structure, the ischiopubic ramus. Thus, about 30 percent of the penis is buried in the pelvis behind the pubic bone. This bony anchor is very important for normal penile function. Where the corpora cavernosa merge at about the level of the pubic bone, the midline surface between the two cylinders forms an incomplete septum. This is important in that it allows blood to pass freely from one corporal body to another.A single corpus spongiosum is located below the junction of the two corpora cavernosa. This simple tube encloses the urethra and at its tip forms the glans penis, commonly referred to as the “head” of the penis. The urethra extends from the bladder to the tip of the glans penis.
The spongy erectile tissue within the three cylinders consists of a mass of smooth muscle, often referred to as trabecular smooth muscle, within which is embedded a network of endothelial lined vascular spaces called sinusoids or lacunar spaces.
Surrounding each of the corpora cavernosa is the tunica albuginea, a dense, multi-layered, collagenous sheath that gives the penis flexibility, rigidity and tissue strength. During an erection, one layer of the tunica albuginea stretches lengthways, which allows the penis to become longer, and the other layer stretches crossways, which allows the penis to become thicker. The third cylinder, the corpus spongiosum, is outside the tunica albuginea and does not become rigid. In addition, all three cylinders are covered by a second, less-dense sheath called Buck’s fascia.
Penile Blood Supply
Blood supply to the penis originates from the right and left internal arteries. These arteries are branches of the major blood supply to the pelvis and in turn branch into the deep penile artery that supplies the corpora cavernosa through small vessels known as Helisine arteries or arterioles. In the flaccid state, the small arterioles are contracted and restrict the arterial inflow into the lacunar spaces. In the erect state, relaxation of the small Helisine arteries allows a rapid increase in blood inflow and exposure of the lacunar spaces (sinusoids) to systemic blood pressure. Another branch of the penile artery, the dorsal artery, supplies the glans and the penile skin. The third branch, the bulbourethral artery, supplies the corpus spongiosum.The most important feature of the venous drainage system is that the tunica albuginea a network of veins, the sinusoidal venules from the lacunar spaces, drains the erectile cylinders when the penis is flaccid. These subtunical venules merge to form emissary venules that exit through the tunica albuginea and pass into the larger venous system, both deep and near the surface. During erection, this network is compressed and stretched by trabecular smooth muscle relaxation. The flow of blood in is strong, the flow out of blood is weak, and the result is an erection.
Neurophysiology of Penile Erection
An erection (tumescence) is a neurovascular event, meaning that both the nervous and the circulatory systems are involved. Recent research has identified specific spots in the brain as the integration centers for sexual drive and sexual arousal, perhaps triggered by psychological factors such as erotic fantasies or expectations. Sensory factors such as audiovisual stimulation also have input through these same brain centers. The brain then controls the penis through two kinds of nerves, autonomic and somatic.Autonomic nerves are not controlled by the individual and are “automatic” in their timing and function. There are two types: parasympathetic and sympathetic. The parasympathetic nerve fibers originate from the sacral spinal cord, at levels 2, 3 and 4 (S2-4). The sacral parasympathetic input initiates erections. The sympathetic nerves meanwhile originate from the eleventh and twelfth thoracic levels of the spinal segments, as well as the first and second lumbar spinal segments. This thoracolumbar sympathetic pathway controls detumescence and orgasm. In other words, parasympathetic autonomic nerves get it up; sympathetic autonomic nerves let it down and keep it down. As we shall see, complex chemical interactions are involved in this process, which is where Viagra comes into play.
Somatic nerves control sensory and motor functions of the body. Sensory receptors on the glans penis and the penile skin lead to sensory nerves that converge to form the primary dorsal nerve of the penis; this becomes the pudendal nerve which courses up to the sacral segments S2, 3,4.
As noted above, during an erection the penis is transformed from a venous to an arterial organ. Blood flow into the penis is controlled by three neurotransmitter systems: adrenergic nerve fibers; cholinergic nerve fibers; and nonadrenergic-noncholoinergic (NANC) fibers that release nitric oxide (NO). The exact nerve-chemical processes are very complex.
Expressed in its simplest terms, in the body, certain smooth muscle cells (those muscles we cannot control, as opposed to skeletal muscles) respond to chemical signals released by different nerves. In the penis, these chemicals normally keep the penile erectile tissue in the flaccid condition by keeping the smooth muscle cells contracted. But when the conscious or unconscious brain begins to be sexually stimulated, other chemicals are manufactured, which react with the penile erectile tissue (primarily smooth muscle cells) to set up the sequence of events that leads to an erection.
Thus, a series of coordinated vascular events, controlled by autonomic nerves, leads to an erection: relaxation of the smooth muscle in the sinusoids in the corpus cavernosum; increased arterial inflow; and occlusion of the venous drainage from within the erectile spaces. In addition to the vascular components of an erection, there are skeletal-muscular components as well, which are controlled by the somatic (sensory and motor) nerves. These skeletal components play a role in the rigid erection phase.
You can see the interplay of all these actions in the following summary of the phases of erection:
FLACCID PHASE: When the penis is resting, the trabecular smooth muscle within the corpus cavernosum is contracted and arterial blood inflow is minimal, while venous outflow is quite rapid. The blood pressure in the intracorporal space is therefore low, about 4-6 mm of Hg.
INITIAL FILLING PHASE: The parasympathetic nerve stimulation now relaxes the smooth muscle of the small arteries and arterioles resulting in a four to tenfold increase of arterial flow into the penis. Simply put, the penis is rapidly filling up with blood. The increased blood volume in the sinusoids initiates the venous occlusion process due to the stretching of the small veins below the tunica albuginea surface. In this initial filling phase there is very little change in pressure within the two corpora cavernosa.
TUMESCENCE PHASE: In this phase the volume of blood progressively increases and the pressure begins to increase inside each corpus cavernosum. The clamping down of the small veins below the tunica albuginea continues as the pressure increases. As the overall pressure builds up inside the erectile cylinders, the arterial inflow begins to diminish.
FULL ERECTION PHASE: In this phase the trabecular smooth muscle is fully relaxed and the corpus cavernosum is full with newly infused arterial blood. The arterial inflow is now minimal. The penis is rigid. The venous occlusion mechanism is in full force with no venous drainage. The pressure inside the corpus cavernosum is equal to the average arterial pressure, about 100 mm of Hg.
RIGID ERECTION PHASE: During this phase the pressure inside the corpora cavernosa may temporarily increase to several hundred mm of Hg due to contraction of the pelvic floor muscle outside the penis (ischiocavernosus muscle). Arterial inflow is still zero. The somatic penile nerves, primarily in the engorged, supersensitive glans penis, contribute to the sacral nerves to stimulate the pudendal motor nerve which is responsible for contraction of both the ischiocavernosus and bulbocavernosus muscles. A rhythmic contraction of the latter muscle is necessary for ejaculation.
DETUMESCENCE PHASE: Sympathetic (adrenergic) stimulation causes contraction of the trabecular smooth muscle. Very rapidly the venous outflow is re-established. The penis then returns to the flaccid phase.
Keep in mind that the major elements of the erection process are occurring in the two erectile cylinders, the corpora cavernosa. During erection, blood flow certainly also increases to the corpus spongiosum tissue around the urethra and to the glans penis. However, the absence of any tunica albuginea in the covering of the glans penis and the presence of only a very thin tunica covering over the corpus spongiosum means there is no significant venous occlusion. Without the thick tunica covering against which the blood veins of the corpora cavernosa are flattened, there is little increased pressure in the glans and in the third penile cylinder. But, during the rigid erection phase, contraction of the ischiocavernosus muscle and bulbocavernosus muscle do compress the spongiosum and penile veins and result in a measurable change in warmth and tone in the head of the penis.
Nerve/Chemical Interaction With Erectile Tissue
Adrenergic nerves constrict penile blood vessel and corpora cavernosum smooth muscle via alpha-1 adrenoreceptors. Norepinephrine is the neurotransmitter. Blood vessel and smooth muscle relaxation are controlled by cholinergic (with acetylcholine as a neurotransmitter from parasympathetic nerves) and nonadrenergic-noncholinergic (NANC) fibers. Some of the NANC fibers may contain vasoactive intestinal polypeptide. Vasodilation of the penile vascular structures, from primarily cavernous smooth muscle relaxation, following activation of cholinergic and NANC fibers is mediated by nitric oxide and its second messenger cyclic guanosin monophosphate (CGMP).
Second-messenger molecules like cGMP function at the molecular level inside the cell in which they reside, in this case the smooth muscle of the corpora cavernosum. We now see that the NANC neurotransmitter nitric oxide (NO) is critical in producing smooth muscle relaxation and penile erection. NO production (synthesis) results from activation of neurogenic and to a small degree, endothelial NO synthase. Once NO diffuses into the smooth muscle cell, it binds to an enzyme guanylyl cyclase. This causes an increase in guanylyl cyclase activity, resulting in cyclic GMP (cGMP) production or synthesis. This intracellular second messenger then carries out the final step in relaxing smooth muscle, reducing the level of intracellular calcium by binding to cGMP-dependent protein kinases, cGMP-dependent ion channels, and cGMP-regulated phosphodiesterases. The overall amount of intracellular cGMP, is controlled by and regulated by the activity of the phosphodiesterase 5, which helps convert cGMP back to GMR Several other forms of phophodiesterase (PDE) have been identified in penile tissue (types 2, 3, 4 and 5); however, PDE 5 is the predominant phosphodiesterase in human corpus cavernosum and human corpus cavernosa smooth muscle. It also is apparently located just in human penile tissue. Viagra functions to block PDE 5. This allows cGMP levels to remain high and continue their function as a smooth muscle relaxant that potentiates and maintains the penile erection.
