Male Sexual Anatomy
MALE SEXUAL ANATOMY
MALE EXTERNAL GENITALIA:
Penis & Scrotum
The penis (shaft) and scrotum (balls) are the external sexual organs of men.
The glans is clearly visible in illustration (A) as the head of the penis. The glans is usually covered by the prepuce unless the penis is erect, except in circumcised men, whose foreskin has been surgically removed. The glans is highly sensitive, as is the corona that connects the glans to the shaft of the penis.
The 'crown,' a ridge of flesh demarcating where the head of the penis and the shaft join.
A thin strip of flesh on the underside of the penis that connects the shaft to the head.
A roll of skin which covers the head of the penis. It is rich in nerve endings. Surgical excision (removal) of the foreskin of men is called circumcision.
The opening at the tip of the penis to allow the passage of both urine and semen.
A substance with the texture of cheese secreted by glands on each side of the frenulum in uncircumcised men.
The scrotum is a sac that hangs behind and below the penis, and contains the testes (testicles), the male sexual glands. The scrotum's primary function is to maintain the testes at approximately 34 C, the temperature at which the testes most effectively produce sperm.
MALE INTERNAL GENITALIA
The male sexual glands, the two testes within the scrotum produce sperm and testosterone. Within each testis is a kilometer of ducts called the seminiferous tubules, the organs which generate sperm. Each testicle produces nearly 150 million sperm every 24 hours.
The epididymis is a 'holding pen' where sperm produced by the seminiferous tubules mature. The sperm wait here until ejaculation or nocturnal emission.
The ducts leading from the epididymis to the seminal vesicles. These are the ducts that are cut during the procedure known as vasectomy.
The seminal vesicles produce semen, a fluid that activates and protects the sperm after it has left the penis during ejaculation
Also produces a fluid that makes up the semen. The prostate gland also squeezes shut the urethral duct to the bladder, thus preventing urine from mixing with the semen and disturbing the pH balance required by sperm.
The corpora cavernosa are the two spongy bodies of erectile tissue on either side of the penis which become engorged with blood from arteries in the penis, thus causing erection.
The path through the seminal glands which semen travels during ejaculation.
The Cowper's glands secrete a small amount of pre-ejaculate fluid prior to orgasm. This fluid neutralizes the acidity within the urethra itself.
FREQUENTLY ANSWERED QUESTIONS
What's the average size of the penis? What are the extremes?
According to the book Mandens Krop (which is translated from English, but does not give the original title) the average is 15cm and 90% are between 13 and 18cm.
The records for a fully functional penis are 1.5cm and 30cm.
Is penis size important?
This is probably one of the most frequently asked questions on alt.sex, and that's a shame, because it's really a pointless question. Penis size is important if and only if you think it is. If you have sex with men and you desire a large penis, then penis size is important to you, and only to you. If you feel your penis should be larger, then penis size is important to you, and only to you.
Many women report that too many men are hung up on the size of their penises. The vagina is only eight to thirteen centimeters long, and even a small penis can touch every square centimeter within the vagina.
Can penis size be increased?
Yes. There are two surgical procedures to increase penis size-- the Bihari Procedure, and Fat Injection.
The Bihari Procedure consists of cutting the ligament that secures the base of the penis to the body. This gives between one-half and two inches of increased length to the penis; however, because the penis is no longer anchored to the body an erection no longer points 'up.'
Fat Injection is the process of removing fat from the backs of the thighs and injecting it into the body of the penis to make the penis thicker. Because the body rejects a significant portion of the injection this procedure may need to be repeated several times and each operation carries with it a severe risk of infection.
How do I measure my penis?
According to Harold Reed, M.D., director of the Reed Centre for Ambulatory Urological Surgery in Bay Harbor, Florida, this is the correct way to measure the length of your penis:
First, while standing, get an erection. Okay, now gently angle your, er, equipment down until it is parallel to the floor. Set your ruler against your pubic bone just above the base of the penis, and measure to the tip. Thats how the doctors do it.
My penis bends down (or left, or right). Is there something wrong with it?
One-quarter of all penises bend in some direction and some bend downward even when erect. Unless the bend is severe or causes you pain, there is nothing wrong or abnormal about your penis. It should not interfere with sexual intercourse. Some people report that a downward-bending penis is easier to fellate.
In rare cases a condition called Peyrone's Syndrome can arise from childhood diseases. This condition is caused by scarring on one of the two corpora cavernosa within the penis, stunting its effectiveness during erection and causing the penis to bend almost 90 degrees in that direction. If you feel this may be the case, consult a urologist.
What is circumcision and why is it done?
Male circumcision is the surgical removal of the foreskin from the penis. When performed in a hospital, it is usually done shortly after birth by a doctor or midwife. Circumcisions are also given to Jewish boys by a mohel in a ceremony eight days after birth. Some Islamic boys are circumcised when they are older, around age 12. The majority of American boys are circumcised.
Common reasons for circumcision include: religious beliefs; better hygiene, "normal" or "better" appearance, and "his penis should look like his father's."
Common reasons against circumcision include: it is no longer necessary for hygienic reasons; it is a painful, barbaric practice; there is a possibility of infection or surgical error; destruction of sexual tissue reduces sexual sensitivity; "normal" or "better" appearance; and "his penis should look like his father's."
What are blue balls?
Blue Balls is a real condition! The "correct" term for blue balls is epididymitis, which is an inflammation of the epididymis.
In simple terms blue balls occurs when the epididymis get blocked up with sperm that have left the testis but not the penis. The vas deferns are the conduit for the sperm from the testis to the urethra. When they get blocked you get pain. Why blue balls and not "swollen balls," well maybe the connotation is that you balls have the "blues", or maybe its because with all that swelling some of the blood flow is restricted enough to cause some blueing of the area because of pooling blood.
Why is the prostate mentioned so often during discussions of anal sex?
The prostate is about the size of a walnut in a normal man, and is immediately behind the rectal wall about three centimeters inside the anus. It can be felt by placing one finger within the anus and feeling along the anterior wall for a round bulb. For some men, touching or rubbing this spot is extremely pleasurable; a rare few can even orgasm through this technique. Others report that the touch is painful or makes them feel as if they need to urinate.
MALE EXTERNAL SEXUAL ANATOMY
The penis is a man’s reproductive and sex organ. It is formed of three columns of spongy tissue — the corpus spongiosum and two corpora cavernosa — that fill with blood during sexual excitement, causing an erection (“hard on”). The penis extends from the lower portion of the belly. It is made up of a shaft and a glans (also known as the head) and is very sensitive to the touch. A man’s urethra is enclosed in his penis. It carries urine, pre-ejaculate, and semen out of his body.
The shaft looks like a tube. The shaft of the penis is about 1–3 inches long when soft. During an erection, the shaft expands to generally reach 4–6 inches.
The glans is the soft and highly sensitive part of the penis, located at its tip.
Opening of the Urethra
The opening of the urethra is located at the tip of the penis. This is where pre-ejaculate, semen, and urine leave the body.
The foreskin is a retractable tube of skin that covers and protects the head (glans). Some men have had their foreskin removed by circumcision during infancy. Some choose to be circumcised later in life.
The frenulum is where the foreskin attaches to the underside of the penis just below the glans. Usually, a portion of it remains after circumcision.
The scrotum is a sac of skin divided into two parts, enclosing the internal reproductive organs — the testicles.
MALE INTERNAL SEXUAL ANATOMY
The testicles are two ball-like glands inside the scrotum that produce sperm and hormones, including testosterone. Also called testes, the testicles are sensitive to the touch.
The epididymis is the tube in which sperm mature. An epididymis leads from each testicle to each vas deferens. It stores sperm before ejaculation. It is tightly coiled on top of and behind each testicle.
The muscle that automatically brings the testicles closer to the body as temperatures get colder or when the front or inner surface of the thigh is stimulated. The automatic response of the cremaster muscle is called the cremaster reflex. (If only one thigh is stimulated, only the testicle closest to the stimulated thigh is elevated.)
A vas deferens is a long, narrow tube that carries sperm from the epididymis to the seminal vesicles during ejaculation. There are two of them — one connected to each epididymis.
The prostate gland produces a fluid that helps sperm move through a man’s reproductive tract. The prostate gland is about the size of a walnut or golf ball. The prostate is sensitive to pressure and to the touch — “the male G-spot.”
The Cowper’s glands are beneath the prostate and attach to the urethra. They produce a fluid — pre-ejaculate or pre-cum — that prepares the urethra for ejaculation. Pre-ejaculate reduces friction in the urethra, making it easier for semen to pass through. Cowper’s glands are also called bulbourethral glands.
Seminal vesicles are two small organs that produce seminal fluid. The seminal vesicles are located below the bladder.
The urethra is a tube that empties the bladder and carries urine, pre-ejaculate, and semen to the urethral opening.
OTHER PARTS THAT ARE SEXUAL
When it comes to sex, women and men are more alike than they are different. In many ways, for example, the brain can be said to be our most important sex organ. The brain controls our sexual responses, releases sex hormones, and it is where all our sex fantasies, and sexual identities live. This is just as true for women as it is for men.
Skin is the largest organ of the body. It carries a network of highly sensitive nerves all over our bodies, so that any body part may be stimulated for sexual arousal. In this way, too, our skin is our biggest sex organ. This also is just as true for men as it is for women.
Any part of the body that is sensitive to sensual touch — whether or not it is part of our sex anatomy — is called an “erogenous zone.” For both women and men, this may include our breasts and nipples, our anuses, the backs of our necks, our lips, our mouths and tongues, the smalls of our backs, our fingers and toes, the palms of our hands, the soles of the feet, the lobes of our ears, our inner thighs, etc. Some of these may be erogenous zones for many of us.
The scrotum is a sac-like organ made of skin and muscles that houses the testes. It is located inferior to the penis in the pubic region. The scrotum is made up of 2 side-by-side pouches with a testis located in each pouch. The smooth muscles that make up the scrotum allow it to regulate the distance between the testes and the rest of the body. When the testes become too warm to support spermatogenesis, the scrotum relaxes to move the testes away from the body’s heat. Conversely, the scrotum contracts to move the testes closer to the body’s core heat when temperatures drop below the ideal range for spermatogenesis.
The 2 testes, also known as testicles, are the male gonads responsible for the production of sperm and testosterone. The testes are ellipsoid glandular organs around 1.5 to 2 inches long and an inch in diameter. Each testis is found inside its own pouch on one side of the scrotum and is connected to the abdomen by a spermatic cord and cremaster muscle. The cremaster muscles contract and relax along with the scrotum to regulate the temperature of the testes. The inside of the testes is divided into small compartments known as lobules. Each lobule contains a section of seminiferous tubule lined with epithelial cells. These epithelial cells contain many stem cells that divide and form sperm cells through the process of spermatogenesis.
The epididymis is a sperm storage area that wraps around the superior and posterior edge of the testes. The epididymis is made up of several feet of long, thin tubules that are tightly coiled into a small mass. Sperm produced in the testes moves into the epididymis to mature before being passed on through the male reproductive organs. The length of the epididymis delays the release of the sperm and allows them time to mature.
Spermatic Cords and Ductus Deferens
Within the scrotum, a pair of spermatic cords connects the testes to the abdominal cavity. The spermatic cords contain the ductus deferens along with nerves, veins, arteries, and lymphatic vessels that support the function of the testes.
The ductus deferens, also known as the vas deferens, is a muscular tube that carries sperm superiorly from the epididymis into the abdominal cavity to the ejaculatory duct. The ductus deferens is wider in diameter than the epididymis and uses its internal space to store mature sperm. The smooth muscles of the walls of the ductus deferens are used to move sperm towards the ejaculatory duct through peristalsis.
The seminal vesicles are a pair of lumpy exocrine glands that store and produce some of the liquid portion of semen. The seminal vesicles are about 2 inches in length and located posterior to the urinary bladder and anterior to the rectum. The liquid produced by the seminal vesicles contains proteins and mucus and has an alkaline pH to help sperm survive in the acidic environment of the vagina. The liquid also contains fructose to feed sperm cells so that they survive long enough to fertilize the oocyte.
The ductus deferens passes through the prostate and joins with the urethra at a structure known as the ejaculatory duct. The ejaculatory duct contains the ducts from the seminal vesicles as well. During ejaculation, the ejaculatory duct opens and expels sperm and the secretions from the seminal vesicles into the urethra.
Semen passes from the ejaculatory duct to the exterior of the body via the urethra, an 8 to 10 inch long muscular tube. The urethra passes through the prostate and ends at theexternal urethral orifice located at the tip of the penis. Urine exiting the body from the urinary bladder also passes through the urethra.
The prostate is a walnut-sized exocrine gland that borders the inferior end of the urinary bladder and surrounds the urethra. The prostate produces a large portion of the fluid that makes up semen. This fluid is milky white in color and contains enzymes, proteins, and other chemicals to support and protect sperm during ejaculation. The prostate also contains smooth muscle tissue that can constrict to prevent the flow of urine or semen.
The Cowper’s glands, also known as the bulbourethral glands, are a pair of pea-sized exocrine glands located inferior to the prostate and anterior to the anus. The Cowper’s glands secrete a thin alkaline fluid into the urethra that lubricates the urethra and neutralizes acid from urine remaining in the urethra after urination. This fluid enters the urethra during sexual arousal prior to ejaculation to prepare the urethra for the flow of semen.
The penis is the male external sexual organ located superior to the scrotum and inferior to the umbilicus. The penis is roughly cylindrical in shape and contains the urethra and the external opening of the urethra. Large pockets of erectile tissue in the penis allow it to fill with blood and become erect. The erection of the penis causes it to increase in size and become turgid. The function of the penis is to deliver semen into the vagina during sexual intercourse. In addition to its reproductive function, the penis also allows for the excretion of urine through the urethra to the exterior of the body.
Semen is the fluid produced by males for sexual reproduction and is ejaculated out of the body during sexual intercourse. Semen contains sperm, the male reproductive gametes, along with a number of chemicals suspended in a liquid medium. The chemical composition of semen gives it a thick, sticky consistency and a slightly alkaline pH. These traits help semen to support reproduction by helping sperm to remain within the vagina after intercourse and to neutralize the acidic environment of the vagina. In healthy adult males, semen contains around 100 million sperm cells per milliliter. These sperm cells fertilize oocytes inside the female fallopian tubes.
Spermatogenesis is the process of producing sperm and takes place in the testes and epididymis of adult males. Prior to puberty, there is no spermatogenesis due to the lack of hormonal triggers. At puberty, spermatogenesis begins when luteinizing hormone (LH) and follicle stimulating hormone (FSH) are produced. LH triggers the production of testosterone by the testes while FSH triggers the maturation of germ cells. Testosterone stimulates stem cells in the testes known as spermatogonium to undergo the process of developing into spermatocytes. Each diploid spermatocyte goes through the process of meiosis I and splits into 2 haploid secondary spermatocytes. The secondary spermatocytes go through meiosis II to form 4 haploid spermatid cells. The spermatid cells then go through a process known as spermiogenesis where they grow a flagellum and develop the structures of the sperm head. After spermiogenesis, the cell is finally a sperm cell, or spermatozoa. The spermatozoa are released into the epididymis where they complete their maturation and become able to move on their own.
Fertilization is the process by which a sperm combines with an oocyte, or egg cell, to produce a fertilized zygote. The sperm released during ejaculation must first swim through the vagina and uterus and into the fallopian tubes where they may find an oocyte. After encountering the oocyte, sperm next have to penetrate the outer corona radiata and zona pellucida layers of the oocyte. Sperm contain enzymes in the acrosome region of the head that allow them to penetrate these layers. After penetrating the interior of the oocyte, the nuclei of these haploid cells fuse to form a diploid cell known as a zygote. The zygote cell begins cell division to form an embryo.
The purpose of the organs of the male reproductive system is to perform the following functions:
- To produce, maintain, and transport sperm (the male reproductive cells) and protective fluid (semen)
- To discharge sperm within the female reproductive tract during sex
- To produce and secrete male sex hormones responsible for maintaining the male reproductive system
Unlike the female reproductive system, most of the male reproductive system is located outside of the body. These external structures include the penis, scrotum, and testicles.
Penis: This is the male organ used in sexual intercourse. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped part at the end of the penis. The glans, also called the head of the penis, is covered with a loose layer of skin called foreskin. This skin is sometimes removed in a procedure called circumcision. The opening of the urethra, the tube that transports semen and urine, is at the tip of the penis. The glans of the penis also contains a number of sensitive nerve endings.
The body of the penis is cylindrical in shape and consists of three circular shaped chambers. These chambers are made up of special, sponge-like tissue. This tissue contains thousands of large spaces that fill with blood when the man is sexually aroused. As the penis fills with blood, it becomes rigid and erect, which allows for penetration during sexual intercourse. The skin of the penis is loose and elastic to accommodate changes in penis size during an erection.
Semen, which contains sperm (reproductive cells), is expelled (ejaculated) through the end of the penis when the man reaches sexual climax (orgasm). When the penis is erect, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.
Scrotum: This is the loose pouch-like sac of skin that hangs behind and below the penis. It contains the testicles (also called testes), as well as many nerves and blood vessels. The scrotum acts as a "climate control system" for the testes. For normal sperm development, the testes must be at a temperature slightly cooler than body temperature. Special muscles in the wall of the scrotum allow it to contract and relax, moving the testicles closer to the body for warmth or farther away from the body to cool the temperature.
Testicles (testes): These are oval organs about the size of large olives that lie in the scrotum, secured at either end by a structure called the spermatic cord. Most men have two testes. The testes are responsible for making testosterone, the primary male sex hormone, and for generating sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubes are responsible for producing sperm cells.
The internal organs of the male reproductive system, also called accessory organs, include the following:
Epididymis: The epididymis is a long, coiled tube that rests on the backside of each testicle. It transports and stores sperm cells that are produced in the testes. It also is the job of the epididymis to bring the sperm to maturity, since the sperm that emerge from the testes are immature and incapable of fertilization. During sexual arousal, contractions force the sperm into the vas deferens.
Vas deferens: The vas deferens is a long, muscular tube that travels from the epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports mature sperm to the urethra, the tube that carries urine or sperm to outside of the body, in preparation for ejaculation.
Ejaculatory ducts: These are formed by the fusion of the vas deferens and the seminal vesicles (see below). The ejaculatory ducts empty into the urethra.
Urethra: The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of ejaculating semen when the man reaches orgasm. When the penis is erect during sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.
Seminal vesicles: The seminal vesicles are sac-like pouches that attach to the vas deferens near the base of the bladder. The seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move. The fluid of the seminal vesicles makes up most of the volume of a man's ejaculatory fluid, or ejaculate.
Prostate gland: The prostate gland is a walnut-sized structure that is located below the urinary bladder in front of the rectum. The prostate gland contributes additional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. The urethra, which carries the ejaculate to be expelled during orgasm, runs through the center of the prostate gland.
Bulbourethral glands: Also called Cowper's glands, these are pea-sized structures located on the sides of the urethra just below the prostate gland. These glands produce a clear, slippery fluid that empties directly into the urethra. This fluid serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra.
Follicle-stimulating hormone is necessary for sperm production (spermatogenesis), and luteinizing hormone stimulates the production of testosterone, which is also needed to make sperm. Testosterone is responsible for the development of male characteristics, including muscle mass and strength, fat distribution, bone mass, facial hairgrowth, voice change, and sex drive.