Penis Anatomy
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The Human Penis
The penis is a male reproductive organ containing the urethra which is used as a passage way for semen (sexual activity) and urine (excretion). In its flaccid state, the penis is cylindrical in shape and soft. When it is erect caused by sexual arousal and stimulation, the penis elongates and expands due to blood flow in penis tissues. The penis is usually measured in its flaccid and erect state and it reaches its full size during the period of puberty. Right now, there are scientific and natural ways on how men can add size to the human penis.
Parts of the Human Penis
The human penis can be divided into two main parts namely: radix penis and corpus penis.
The radix penis is the root part of the penis which is triradiate in form. In the middle of it is the urethral bulb surrounded on both sides by diverging crura. Bulbocavernosus also surrounds the bulb where each of the crus is covered by ischiocavernosus. This part of the organ is suspended on the pubic arch and attached with the help of the suspensory ligaments. Encircling the root of the penis are the fundiform ligaments. These suspensory ligaments have upper fibers that pass downward from the linea alba and symphysis pubis. This results to a fibrous band which is strong enough to hold the entire penis.
Simply called the body of the penis, the corpus penis is identified extending from the root to the end of the corpora cavernosa penis. The dorsal vein of the penis is located inside the junction on the upper surface of the penis which is described as a shallow groove. On the other hand, the corpus cavernosum urethra is marked by a wider and deeper groove.
During erection, the end of the corpus cavernosum urethra or the glans penis expands and forms the extremity. The neck of the penis overhung by the corona glandis seems to separate the body of the penis to the extremity. The skin covering it is looser to its attachment to the head and can be easily identified with its dark color and thinness. However, this skin is attached to the body extending to the penis root. When the penis becomes flaccid, the body of the penis shrinks and this skin is folded which is referred to as the foreskin or prepuce.
When penis is uncircumcised during adulthood, the prepuce extends continuously from the neck of the penis over the glans or head of the penis. This fold of skin forms a secondary duplication behind the external urethral orifice extending from meatus to the neck, which is referred to as the frenulum. The foreskin or prepuce is not considered as a flap as others call it. It is also wrong that people think of the prepuce as a useless piece of skin.
Structure of the Penis
Basically, the penis has the following structures:
Glans (head of the penis) – this is the pinkish head of the penis similar to the head of a mushroom separated by a neck openly seen with a circumcised penis while covered by prepuce when flaccid in uncircumcised penis. The glans in uncircumcised males is covered with mucosa – a moist tissue which protects it. During circumcision, the head or glans including the neck of the penis is exposed which dries up the mucosa turning into skin.
Corpus Cavernosum – these are two columns of tissue located along the penis sides which accumulates blood during sexual arousal causing erection of the penis.
Corpus Spongiosum – this is a column of tissues which are similar to a sponge located along the penis front and ends at the head of the penis or glans. During erection, it is also filled with blood but keeping the urethra open.
Urethra – this is a tube running through the corpus spongiosum which functions as a passage way of urine for body waste excretion, or semen for sexual activity.
Three columns of tissue actually make up the human penis and these are the two corpora cavernosa and one corpus spongiosum. The two corpora cavernosa lie side by side on the dorsal section while the corpus spongiosum is located between them on the ventral section.
The glans penis looks like a bulb which is located in the end of the corpus spongiosum. This head supports the prepuce while the prepuce protects the head. In circumcision process, the prepuce or the foreskin is removed exposing the head of the penis. On the underside of the penis, you will notice a small foreskin which is similar to the skin under our tongue. This area of the penis is called the frenulum or frenum. The rounded base of the glans attached to the neck of the penis is called corona while the line along the penis underside is referred to as the perineal raphe.
The urethra is not only a part of the penis but it is actually a segment of the urinary tract which runs through the corpus spongiosum. Its opening which looks like a little mouth is called the meatus, which is found on the very tip of the penis head. During ejaculation, semen comes out of the meatus while during urination, urine comes out instead. In the testes, sperm cells are produced which are stored in the epididymis. These sperms are propelled by the vas deferens during ejaculation while fluids coming from seminal vesicles combine with it producing semen.
If the penis is halved laterally, you will see a visible ridge found on the underside or ventral part of the penis. This is what you call the raphe which runs from the meatus across the scrotum to the perineum. Unlike other mammals, the human penis has no erectile bone.
By the event that the man becomes sexually aroused, nerves send stimuli which causes the muscles around penile arteries to relax and accept blood inflow. The sponge-like tissues (corpus spongiosum) traps more blood inside making the penis attain full erection. This is the reason why penis becomes hard, long, thicker, and stiff. In this process, the veins inside the penis become tight so that the blood will not escape out of the penis sustaining the erection needed for sexual intercourse or powerful ejaculation. After a successful ejaculation, the arousal eventually fades which sends signal to the brain and allows the process called detumescence – the blood is allowed to leave the penis tissues which makes the penis return to its flaccid state.
Left: Circumcised penis
Right: Uncircumcised penis
Penis Functions
The penis including the scrotum and the testicles begin to develop at the start of human puberty period. In this process, pubic hair starts to grow around the penis. According to a research, the average penis size of men aged 17 to 19 has no big difference at all. Therefore, penis growth can be complete not later than the age 17.
The male organ is sexually homologous to that of the female sex organ. This means that both organs have evolved from similar types of tissue. The tissues of the glans penis have the same tissues as the clitoral glans which means that these glanses are homologous. The corpus spongiosum and the vestibular bulbs beneath the labia minora are homologous to each other. This is also true with the scrotum of the male and the labia minora and labia majora of the female. The clitoral hood of the female is homologous to the foreskin. Now since the two halves of are not connected, the raphe is not existent on females.
Erection is another function of the penis wherein the penis becomes stiff and rising during sexual excitement or arousal. Erection uses a physiological mechanism called autonomic dilation of arteries so that ample supply of blood is brought to the erectile tissues of the penis. Erection is an integral part in a sexual intercourse though it might not be needed in other sexual activities.
Different kinds of penises when erect can have different angles although we usually see them pointing upwards. Penises when erect can be seen pointing nearly vertically upwards, nearly vertically downwards, or horizontally straight. These are all normal and this depends with the suspensory ligaments that hold the penis.
Coming from a research study, more than 1,500 males aged 20 to 69 were studied concerning their penis angles during full erection. The following table shows the range of angles from 0 to 180 degrees where 0 degree means vertically upwards and 180 degrees is vertically downwards. The right side of the table shows the per cent of men having such erection angle.
| Male Erection Angles | |
| Angle in degrees |
% of Males |
| 0-30 | 5 |
| 30-60 | 30 |
| 60-85 | 31 |
| 85-95 | 10 |
| 95-120 | 20 |
| 120-180 | 5 |
Ejaculation is another important penile function which is needed in sexual intercourse especially when a couple wants to have a baby. Ejaculation means the ejecting of semen (or ejaculate) out of the penis. This is usually accompanied by orgasm. This is the result of sexual stimulation where the sperm cells are delivered with the aid of muscles and other male reproductive parts. Aside from sexual stimulation, it can also be caused by the prostates especially to people with prostatic disease. Wet dreams or nocturnal emissions are ejaculations during REM or sleep. People who are not able to ejaculate are suffering from a condition called anejaculation.
The two phases of ejaculation are emission and ejaculation proper. The symphatetic nervous system is responsible for the ejaculatory reflex during the emission phase. On the next phase, ejaculatory proper, the spinal reflex is responsible. In this phase, the level of the spinal nerves S2-4 by the pudental nerve.
Decorating the penis is not only a modern trend but it has been practiced by certain cultures for centuries. Men decorate their penis by piercing jewelry and sometimes, it can be the subject of body art or body painting. These practices in altering the genitals are universally elective since it can have a purpose for fashion, aesthetics, or sensitivity increase. Here are some of the known penis alterations:
- Penis piercing – this includes types like Prince Albert, ampallang, dydoe apadravya, and frenum piercing.
- Foreskin restoration.
- Shaft implants
- Sex reassignment – results to being a transsexual wherein the penis is transformed into a neovagina
- Penectomy – surgical removal of the penis
- Subincision – urethra is split along the underside of the man’s penis.
- Circumcision
The glans (head of the penis) is designed to increase the chances for egg fertilization during reproduction. It also creates extra sensation or friction during sexual intercourse and acts as a shock absorber within the vagina. The skin of the glans is sensitive and that is why it is normally protected by the prepuce during birth. But with circumcision, the prepuce is removed revealing the glans permanently. To uncircumcised men, the prepuce retracts as the penis erects to reveal the glans.
Circumcision has become popular worldwide especially in the Western societies although it has been widely practiced by Muslims and Jewish people. Many hygienist preferred circumcision since they believe that the penis is easier to keep clean when the foreskin or prepuce is removed. Because of the better hygiene that circumcision brings, many parents and doctors practice and recommend circumcision for males. But people who does not believe in circumcision have also equally kept themselves in proper hygiene having uncircumcised penis.
Today’s modern way of circumcision, there are some old rules in the process are still being followed. For example, the amount of foreskin to be eliminated must be estimated first. By opening the prepuce via the preputial orifice, the glans will be checked if normal because it will be revealed. To continue the process, the preputial epithelium referred to as the foreskin inner lining is separated from its glans attachment. A device called the dorsal slit will be placed to stop the penis blood flow and prevent erection. When everything is ready then the foreskin will be removed.
Anatomical Surgeries for Penis
In September 2005, a penis allotransplant has become successful to a 44-year old man wherein the blockage of his urethra was opened in order for him to urinate. The surgery was done at a military hospital in China and the penis damage was caused by an accident. But two weeks later after the penis surgery, it was reversed due to psychological and marital issues caused by it.
Bioengineered penises have been developed and were successfully implanted on rabbits by researchers Everli, Yoo, Chen, and Atala in 2009. The research was considered successful because the animals with transplanted penises have attained erection and copulate. Ten out of twelve of the rabbits have ejaculated. This study will further lead to artificial penises that can be conducted through phalloplasty in the future.
WORKS CITED
