SexEdNotes   ~   Male Anatomy


In these Anatomy sections, new terms or the names of new body parts will have Leading Caps to emphasize to the reader their significance. Be sure you know what each term or part is as you read through the material.


Secondary Sexual Characteristics - Male:

In most cases, a male human and a female human can be separately identified by the appearance of their genitalia, which are their primary sexual characteristics. However, as the youthful human matures sexually with age, after completing their puberty stage, they can usually be identified by their Secondary sexual characteristics, which are minor characteristics that help to identify a body as a male or a female. Some men may share female characteristics, and the opposite is also true. Typical male secondary characteristics are:

FACIAL HAIR - Generally females do not have facial hair... at least enough to form a mustache or beard. As females age, they do tend to have a little bit of facial hair, but that can be due to her lower levels of estrogen hormone and higher levels of testosterone, brought on by conditions such as menopause. Males from some races have very light beards or no facial hair at all.

BROADER SHOULDERS - This can be exaggerated even more if they do exercises that build their upper-body muscles more than normal. Woman can also over-develop their muscles that tend to give them a more 'masculine' looking body shape.

NARROWER HIPS - The male pelvis is usually more narrow than a female's pelvis. If the male is not overweight he will often have minimal hip dimensions.

DEEPER VOICE - Obviously this is not visible in the images, but males will often have a deeper, lower toned voice than a female.

GREATER DEVELOPMENT OF SKELETAL MUSCLES - The average male will usually have stronger, larger and more defined skeletal muscles. There are some women that develop larger muscles, from exercise and training. Extreme increases  in muscle size over short periods of time may require using steroids or male hormones, but that is not recommended.

MINIMAL DEVELOPMENT OF THE BREASTS - Males generally will not produce milk in their breasts, but can be induced through serious effort. If Anabolic Steroids are used to develop muscles, they often will develop males' breasts.

You can see in the following images that some men show each of these characteristics, more or less than the next man.




The male sexual organs consist of the genitals, which make up the external organs, and the various internal organs that are unseen. Technically referred to as the Pudendum, the term Genitalia comes from 'genit- 'which means "pertaining to organs of reproduction", and consist of the penis and the scrotum.

External Reproductive Organs

Male and female genitalia are genetically different but anatomically the same until the eighth week of fetal development en utero.

The penis has two purposes. First, inside the penis, running the length of the penis, just inside the under-side surface, is the urethra, a tube a little smaller in diameter than a common wooden pencil. That urethra carries the man's urine from his bladder out to the tip or meatus of his penis. There is a valve at the base of the penis that controls the flow of urine.

The second purpose of the penis is to deliver sperm (from the testicles) and semen (from the prostate gland and the seminal vesicles) into the woman's vagina. Together the two fluids are referred to as 'ejaculate'. The semen keeps the sperm alive until it can reach the woman's fallopian tubes where it may meet up with one of her eggs and result in conception which leads to a pregnancy. For the penis to enter the woman's vagina it usually has to become larger and more firm. This change in the penis is referred to as an erection. When the penis is not erect, it is what is referred to as being flaccid.

The penis contains three long cylinders of spongy, erectile tissue that contains blood, and when the man's brain signals a need for an erection it signals valves at the base of the penis that allow the blood to leave the penis to close. That causes blood pressure to build inside those three cylinders (two called corpus cavernosa near the top side and one that surrounds the urethra called corpus spongiosum), which causes the cylinders to become longer, wider, and more firm. That results in the penis doing the same, making it become larger and more firm. This gives the penis the rigidity to slip into the vagina.

These are three views of the same penis going from the flaccid or un-erect stage to the semi-erect stage and then to the fully erect stage. In the semi-erect stage it is gaining length but not yet under enough pressure to lift it and provide rigidity. As you can see, it has become longer when erect. Any penis that is functioning properly will show the same process.

You may also notice that this male has used a razor to remove some of his pubic hair. This is done by choice, for a number of reasons.

Usually, when a penis is of longer than average length when flaccid (not erect), it will not increase in size the percent of increase in length as a shorter penis. A smaller penis will increase a greater percentage of length and width). This penis in these pictures is shorter than the average penis when flaccid, but the average depth of a vagina is about 3 1/2 inches so when this penis is erect it is capable of placing the ejaculate at the deeper end of the vagina, where it has very little difficulty finding the opening to the uterus and starting the journey to the egg.

When the male brain determines there is no longer a need to maintain the erection, it will signal the valves at the base of the penis to dilate or open, allowing the blood in the penis to move through without restriction and that allows the erectile tissues to return to their smaller, less rigid (or flaccid) condition.

When a penis becomes erect, it may be straight as this one is, or it may be curved upward, downward, to the left or to the right. All are normal conditions. They also may be straight but point upward, forward, or downward. All are natural.

A penis will become erect because of sexual stimulation, but will also become erect due to physical stimulation such as touch or temperature changes or physical rubbing of clothing, etc. It also will become erect with a full bladder. Erections can occur during sleep due to a sexually stimulating dream or it can occur during REM portion of sleep.  Most young males will awake in the morning with an erection but urinating will usually cause the erection to subside. A concern of any young man is that the penis may seem to have its own brain and become erect for some unknown reason and they literally have no control over it. That is normal. If their erection lasts longer than four hours without being sexually stimulated, they are warned to seek medical attention immediately . Many causes for this exist, including the use of legal drugs such as Viagra, illicit drugs, or injuries to the penis. This is a condition referred to as Priapism, and can be serious as well as painful, and can cause permanent damage.

An erection can go from flaccid to fully erect (turgid) in less than a minute. In young teens/adults it may occur inside of fifteen seconds. Erections occur in males of any age... infant to aged. Ultrasound has observed male fetuses having an erection while en utero after the second trimester. Some degree of erection will usually accompany an ejaculation.

Phallic growth occurs during the weeks nine through 37 of fetal development, and continues throughout youth and puberty, when it reaches maximum development. The corresponding tissue in the female is the clitoris. Hormones and DNA determine during fetal development whether that tissue will develop to be a clitoris or a penis. Sometimes girls are born with extra long clitorises, and boys may be born with extremely short penises. We are not always All Male or All Female... sometimes we may approach the borderline between them. I'm sure you are acquainted with some women that are extremely masculine or some males that are extremely effeminate. We are all different, remember.

The tissue that forms the Labia Minora on a female is the same as the tissue that closes in on the lower side of the penis, forming closure over the urethra that runs the full length inside the penis. If the closure does not become complete, it forms a Spodia, which essentially is a malformed meatus or opening of the penis. Urine may direct up or down upon exit rather than straight ahead. This is usually corrected during the first year or two of life by plastic surgery. It is suspected to pass genetically but only shows up every other generation... grandfather to grandson basically, through the father,

Back in the thirties and forties a man/wife team made up the Kinsey Institute and they did some very deep studies about our sexuality and our bodies. They determined that the average length of the flaccid penis is four inches. When erect the average is six inches. Ninety percent of all men are between five and seven inches long when erect.

One concern people have about 'pornography' is that they use actors with exceptionally developed features such as breasts and penises. It is a concern of many that young people viewing these films will get the idea that "everyone" has penises that are a foot long or "everyone" has breasts that are size 45 GGG. Some people are concerned that 'normal' young people will see those extreme cases and assume that because the actor's penis is that large or the actress's breasts are that large and their own is/are smaller, they (the observers) are not normal, or they are somehow unfit. Even the images you see here are usually exceptional in many ways, but that is because it is not easy to find internet images that are not a little special. Many 'normal' people would never post their image because they may feel they are not 'good enough' to be seen.

In actuality it is estimated that there are less than 1,000 men with a penis over twelve inches in length. The longest penis of record is... ten feet. But... rest easy. It is on a sperm whale. The record length for a human is said to be 14 1/2 inches in length. Just rest assured... the average vagina is 3 1/2 inches deep., and even the smallest penis can still produce children.

As most men get older, they will find it is usually more difficult to become erect. Medications that they are taking for high blood pressure or high cholesterol or any number of maladies that come with age can be the reason they have difficulty to become erect. Remember, alcohol consumption can also kill the ability to perform sexually. This is what is referred to on TV as ED or Erectile Dysfunction, and they sell little blue pills that often will help facilitate erections. If those don't help, they can implant small cylinders in the penis where the erectile tissue is located and a small pump located in the scrotum allows them the manually make the penis become erect.

The penis cannot be enlarged by creams, exercises, vacuum pumps, hypnosis, etc. Some increase is possible by plastic surgery, by cutting supporting muscles, but an extremely high percentage of these cases are failing, causing serious disfigurement and sometimes even worse than that. Do not be led by the 'hype' that is given about Penile Size. It usually is not women that are 'turned-on' to excessive penile size.

In the image above, notice that the Glans Penis is shrouded with skin. You can only see the very end or tip of the glans. This is an example of an un-circumcised penis. This is the way all males are born. Often times a decision is made to remove the skin covering the glans penis. That skin is known as the prepuce or the foreskin. The procedure to remove the foreskin is called "Circumcision". When the procedure is performed as a Jewish faith ceremony it is done on the eighth day of life and is referred to as B'rit Milah or a Bris. Other cultures do it around the age of fourteen as a ritualistic passing into adulthood. If i is done for other than religious or cultural reasons, it is usally done the first few days of life.

The image on the right is a penis that has been circumcised. Notice the "Circ. Scar" is where the foreskin was once attached. Look back a couple of images at the large image with the parts of the penis spelled out. Notice the rough-looking skin just behind the glans penis? That is actually a scar from where the foreskin was removed surgically, most likely when that male was very young. Parents in the United States usually decide to have the surgery done at a very early age today, if they are going to do it at all. Many leave the foreskin in place.

There are legitimate reasons to remove it and reasons to leave it intact. Left intact is the natural choice, but without proper hygiene practices, smegma (waxy substance) and bacteria can build up under the foreskin to cause inflammation as well as be passed to their sexual partner during sexual contact. Some prefer the appearance of the penis when the foreskin is removed, , but some thought is given to whether the glans tip is rendered somewhat less sensitive when left exposed. Some religious faiths have specific reasons to have it removed. If a parent is uncertain, they can always leave it and allow the boy to make his own decision at a later date. It can always be removed, but it is very difficult to replace it should they wish it to be restored.

If a boy retains his foreskin, he should be taught to retract it past the glans (when it is mature enough to do so) and clean the area well when bathing or showering.

About one third of the males in the world have been circumcised. It is frequently done to  members of the Jewish and Muslim religions and young males in Egypt, Africa, and parts of the world where AIDS are prevalent and personal cleanliness is lacking. It is less frequently done in Europe and Asia than in the United States, where it varies by race and by location, as indicated by Child Trends Data Bank http://www.childtrends.org/?indicators=infant-male-circumcision


"In 2008, the latest data available, white male infants were somewhat more likely than their black counterparts to have been circumcised (63 versus 58 percent, respectively)." 

"Male infants born in the Midwest were about two times more likely than those born in the West to have been circumcised in 2010 (71 versus 40 percent, respectively). That same year, 66 percent of male infants born in the Northeast, and 58 percent of male infants born in the South, were circumcised."

When circumcision is done, the foreskin is surgically removed from the penis. The ring below the glans penis in the picture above is part of the scar from that surgery.  On the image above right, where it is pointed out by the term "Frenulum", the foreskin was attached up closer to the glans. That is actually the most sensitive spot on most males. The skin that is removed is often used by surgeons in making skin grafts over serious wounds.

The glans penis is usually more sensitive than the rest of the penis (with the exception of the frenulum on the circumcised penis) because it contains many more nerve endings per square centimeter than most other skin on the body. The glans receives the most stimulation during coitus (the insertion of the penis into the vagina), and it facilitates a quick orgasm causing the deposition (ejaculation) of sperm into the vagina.

The Scrotum hangs behind and below the penis. It contains the man's two Testes, their individual Epididymis and Spermatic Cord, upon which each testis is supported, and contains blood vessels and nerves going to the testis and the Vas Deferens which carries the Sperm from one Epididymis to one Seminal Vesicle. As you can see in the image above the surface of the scrotum is very irregular. It has the amazing ability to expand and contract automatically to allow the testes to move further from the man's body to allow air to cool the testes, which should remain several degrees cooler than normal body temperature to be able to produce sperm at normal amounts. Or they may be brought closer to the body to be warmed. On the surface you can see the raphe', which is somewhat of a scar that is natural. During development of the male fetus in the uterus, the two sides of the scrotum come together and bond, forming the scrotum. If this person were to have developed as a female, the two sides of skin would not have joined together and they would have formed the Labia Minora (vaginal lips).

Early signs of puberty in a boy can be an enlarging scrotum, a darkening of its color, and more deeply wrinkled surface, and this may occur between the age of nine and fifteen years old.

Usually, the scrotum is lightly covered with pubic hair after puberty. The surface will contain sebaceous glands that secrete a material called Sebum and it has a musky odor. This sebum emits pheromones which can be sometimes detected sub-consciously by other individuals.

It is believed that on a right-handed man his left testicle will hang lower than his right one, and vice versa.

Internal Reproductive Organs

The Testes (tess - tees) or Testicles (or male Gonads) are contained within the scrotum, and produce Testosterone, the male growth hormone, produced from before they are born until death, and it is responsible for the male developing his Male Secondary Sexual Characteristics mentioned above.

One Testis (tess - tee) is approximately 1 1/2 to 2 inches long by one inch in diameter, and weigh 10 to 15 grams or 3/4 ounce in weight... about the size of a jumbo-sized olive. Their volume is 16 to 27 ml or about 5 teaspoons. Their size changes when sexually excited, but physical size has no correlation to the quantity or the quality of sperm they produce. To determine the stage of sexual development a male has reached, a doctor can measure the size of the testes with an Orchidometer. In Greek, Orchis means testicle.

They also produce Spermatozoa (Sperm), from the onset of puberty until death. Sperm is the male sex cell which contains a copy of the male's DNA and must reach the woman's egg and penetrate it before Conception can occur. Each Testes contains about 250 Seminiferous Tubules (which together would reach over 1,000 feet in length) where sperm is formed and matured. About 200 million sperm cells are manufactured every day. Each cell requires 70 days to mature and if they are not released by then they die and are absorbed back into the body. More are generated constantly. A man will never "run out of sperm" unless something mal-functions in his body. The oldest father of record was 92 years old when he fathered a child.

The scrotum controls the Testes' temperature because they must remain 3 to 4 degrees F. cooler than the abdomen for Sperm production to occur. Tight-fitting, vinyl, or non-venting pants can build up heat and reduce men's sperm count. Men trying to produce extra sperm to father a child may need to wear special undergarments that actually cool their scrotum slightly. Temperatures lower than several degrees below body temperature will not produce greater amounts of sperm.

When the male child is developing en utero, their Gonads develop way up inside his abdomen, about where a woman's Gonads (Ovaries) develop. Shortly after birth they descend down a passageway into the scrotum. If both Testes do not come completely into the scrotum, it is called an undecended-testes (Cryptorchidism), and it should be corrected immediately or it will be too warm and may become sterile and will never produce Sperm. It will also increase their risk of Testicular Cancer.

An Orchidectomy is another name for castration, and involves the surgical removal of the Testicle(s). One Testicle can provide enough Sperm and Testosterone if the other is lost. Eunuchs are males that are/were castrated before sexual maturity and are/were used to guard the harems of nobility. They are/were sterile (could not produce sperm) and have a feminine voice and a lack of facial hair. The noblemen may not have known that the eunuchs were able to be sexually active. Since they are/were sterile, no children are born by the harem except those of the King or Nobleman that 'owned' the harem. This was done (they claim it is no longer being done) to young male soprano singers to prevent the voice from changing deeper (caused by testosterone during puberty). A law passed in California in (1902) required male mental institution patients to be castrated to prevent masturbation, which was said to cause the insanity that brought them to be in the institution in the first place.

Testicles are extremely sensitive to pressure. The corresponding tissue in the female is the Ovary, the female Gonad.

Now and then a male's Testes are half Ovary, half Testicle.

When a male fetus is developing en utero, his Testes are developing up in his abdomen, in the place where a female's Ovaries develop (and remain). Before birth the boy's Testes start working their way down to his Scrotum, and sometime shortly before or after he is born his Testes descend into his Scrotum. If they do not descend, they are referred to as 'undescended Testes' and must be brought down by the doctor. If they are not, they will remain in his body, be held at too high of a temperature, and cause problems. He will likely be sterile and his risk of testicular cancer are high.

The Epididymis is located inside the Scrotum, on the back side of each Testicle. It runs the full length of the Testis and contains twenty feet of tightly coiled tubing where the Sperm matures after coming from the Testes. It adds to the Sperm and together makes up about ten percent of the Ejaculate that comes from the Penis when the man reaches Orgasm.

The Spermatic Cord that connects from the body to the Epididymis contains three arteries, multiple veins, lymphatic vessels, nerves and the Vas Deferens for each Testis. It physically supports the Testis and is equally sensitive to pressure as the Testes. If the Testis is flipped or twisted or strangulated, the circulation can be closed off, causing great pain and will cause the death of the Testis. This is often the result of aggressive activity such as contact sports. It may require a doctor to straighten it out. This is one of the reasons young men playing aggressive contact sports are required to wear an athletic supporter, which is also known as a "Jock Strap'. It protects the Testes from moving around a lot, possibly flipping and twisting the Spermatic Cords. Sometimes a "Cup" may also be inserted inside the athletic supporter, to cover over the Penis and the Scrotum, protecting them somewhat from a direct blow from a foot or knee. An athletic supporter will also prevent a larger Penis from slipping out of the leg opening of the shorts sports players wear.

The Vas Deferens is twenty inches long each and connects from each Epididymis inside the Scrotum to a Seminal Vesicle in the pelvis to carry sperm through an inside diameter the size of a human hair. Sperm is seventy days old when it reaches the Seminal Vesicles, and it waits at the Vesicles to be Ejaculated. If this tube or duct is surgically severed inside the Scrotum, it can be cauterized and tied back upon itself to prevent Sperm from leaving the Scrotum during Ejaculation. This procedure is referred to as a Vasectomy and is a means of Sterilizing a male. It is also a simple and quick method of birth-control. A Vasectomy has been reversed, but should be be considered to be permanent.

The Seminal Vesicles produce a heavy, white fluid that is called Semen that carries fructose to keep the Sperm alive while the Sperm is traveling to the woman's Egg. The Semen is alkaline to counter the acidity of the woman's Vagina. The Seminal Vesicles produce about 60 to 70 percent of the Ejaculate that leaves the Penis.

The Prostate Gland is about one inch thick by 1 1/2 inches across... about the size of a walnut. It is between the Urethra in the Penis and the Bowel in the Anus, and can be reached by a doctor's gloved finger, placed in the Anus when he/she does a Prostate Examination, which should be done annually after the age of 40, for changes which could indicate Prostate Cancer. This gland produces an alkaline fluid that is rich in zinc and magnesium and makes up 20 to 30 percent of the Ejaculate. Contraction of the gland is what propels Ejaculate from the Penis during Orgasm, which may be propelled from the Penis a distance from zero to 24 inches, or more.

The Prostate Gland has the Urethra and the Vas Deferens pass through it and it acts as a valve, allowing only one of those vessels to be open at any one time to the Penis. This prevents Urine from flowing during an Orgasm. When a male wakens to a strong Erection and they need to urinate it can be difficult as the Prostate Gland is keeping the Urethra closed because an Erection tells the gland that possibly sexual Coitus is on the way.

The corresponding tissue in the female is in dispute. Some feel there is no corresponding tissue in the female to the Prostate Gland but many feel the vestigial Prostate tissue in a male is similar to what makes up the "G-Spot" that is found in many women.

The Bulbourethral Glands (or Cowper's Glands) provide a small amount of a mucus-like fluid used to lubricate the Urethra before Ejaculation. It may be seen as a small drop of fluid coming from the Urethra shortly before Ejaculation. It has a "street terminology" of "pre-cum", and may contain some Sperm and can cause pregnancy. The corresponding tissue in the female is the Bartholin's Gland.