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The Amazing Anatomy and Physiology of the Sexual
and Reproductive Systems

Female          Male          Intersex

The more you know about your body, the better you can take excellent care of yourself, and the more
knowledge you have to share with your lover. The more you know about your lovers’ body, the more
giving you can be. For your health, confidence and pleasure, endow yourself with knowledge.

The Brain and the Spinal Cord

We receive sexual stimulation in two ways: through the brain, and through the spinal cord. During sexual arousal, the spinal cord functions as an immensely sensitive receptor and transmitter of feeling and sensory stimulation, conducting sexual impulses from the entire body to the nervous system and the brain. Nerve impulses travel from the bodies’ erogenous zones to the sensory cortex of the brain, sequentially activating it in over 80 regions.  

Initial arousal stimulates the hippocampus, where memory is located, and the amygdala, which is involved in processing emotions. During intense stimulation and orgasm, the cerebellum, which is responsible for muscular tension, is activated. As orgasm occurs, the hypothalamus excretes hormones, and the nucleus accumbens, the brain’s pleasure center, reaches its activity peak. 

←Two glands located in the brain, the pituitary and hypothalamus

glands, are intrinsic to the endocrine and hormonal systems. These

play a large role in reproduction, the formation of the sexual organs, and sexual

and desire.  

Fantasy is an immensely potent product of

the brain. With it we can create an inner

world of fiery passions and thrilling sensations

through sensory memory and the imagination.

In this inner world we can have many lovers, play many roles, and take prolonged journeys into the erotic.

These functions make the brain our powerhouse sexual organ. The intense sexual activity of the brain is the main reason why some people can have orgasms solely through fantasy and internal stimulation, without physical touch.

The brain is also profoundly influenced by social conditioning, the values and beliefs of our family, friends, and culture. Social conditioning can foster sexual wellbeing by instilling positive messages about sex in the psyche, or it can destroy sexual wellbeing by instilling negative messages.

Positive messages which make us feel good about our body, it's functioning, and our sexual expression allow us to blossom into people who are comfortable with their sexuality. Conversely, negative messages about sex can thwart our sexual wellbeing by instilling shame, guilt, fear, or other harmful attitudes towards sexual feelings and experiences.


Female Sexual and Reproductive Anatomy



Vulva is the inclusive name of all the external female genitalia. Like individual hands or faces, each woman's vulva is unique, beautiful, and expressive. With the exception of the mons and the outer lips, the vulva is covered with permeable mucosal tissue. 

Mons (Mound of Venus)

The mons is the lovely curving circular mound over the pubic bone that is usually overlaid with pubic hair. It has regular epidermal skin rather than the mucosal tissue that covers most of the genitalia. A layer of fat in the mons gives the pubic bone some protection from impact during physical activity.




  1: fallopian tube, 2: bladder, 3: pubic bone,  4: g-spot, 5: clitoris, 6: urethra,
7: vagina, 8: ovary, 9: sigmoid colon, 10: uterus,   11: fornix, 12: cervix, 13: rectum, 14: anus ,

The clitoris is the primary organ in female orgasm. The vast majority of women experience orgasm principally from clitoral stimulation. Made of erectile tissue, the clitoris is the only organ known to exist sheerly for sexual pleasure, serving no other function. It can vary considerably in size, shape and color from individual to individual. 

The head - or glans - of the clitoris is often mistaken for the entire clitoris. But → actually the entire clitoris is a much larger organ; the erectile tissue of the clitoris continues as an internal structure that is around the same size as the male genitalia. Elegantly fashioned, it is made up of interlinked components: glans (head), hood, shaft, crura, and bulbs. 

Clitoral Glans (Head)

The nerve-rich clitoral glans at the tip of the clitoral shaft has twice the nerve endings of any other part of the human body, including the penis. A round or bulbous head about the size of a wild pearl, it nestles under the clitoral hood. The clitoral glans is exquisitely sensitive to stimulation.  

Clitoral Hood (Prepuce)

The clitoral hood is a protective foreskin that partially covers the clitoral glans and connects with the fourchette and labia minor. The hood can be manually retracted so that the clitoral head can be directly stimulated. Movement of the attached labium and fourchette can cause the clitoral hood to rub against the clitoral glans pleasurably. 

Clitoral Shaft

The clitoral shaft is a firm cylinder-like tube full of spongy tissue which engorges with blood and becomes erect when erotically stimulated. You can feel it very distinctly with your hand if you touch your clitoral head and then follow the connected shaft back towards the mons; this part of the shaft can be seen externally. The rest of the shaft continues inside the internal structure of the sexual system. 

Crura (Crus)

The Crura, or Crus, is made of erectile tissue which extends like two slender legs or tendrils from the clitoral shaft down through the lips of the labia minora. They are highly sensitive to stimulation felt through the labia and connected areas. 

Clitoral Bulbs

The clitoral or vestibular bulbs lie beneath the labia minor and surround the vaginal opening. They engorge and expand during sexual arousal, providing pleasure when receiving stimulation from activity in the vaginal opening or lower vaginal canal. 


Smegma is a natural accumulation of vaginal secretions that form into a white paste, found under the vaginal hood around the base of the clitoral head, and sometimes in the labial folds. It begins as Sebum, a fluid the body creates to lubricate the clitoris. When it is left to thicken, it becomes Smegma. 

Smegma is a medium for excess bacterial growth which can become infected,

and when it builds up it can become a binding adheson that prevents movement between the clitoral hood and the clitorice (ouch!). To prevent this, it should be cleaned off on a regular basis. Open the folds of the labia and gently retract the clitoral hood to wash with mild, unscented soap and water. Don’t use harsh or perfumed soap. 

Labia Majora (Outer Labia)

The labia majora are the fleshy “outer lips” of the vulva.  Varying greatly in size from body to body, the labia majora is covered by regular epidermal skin rather than mucosal tissue. The labia majoras’ beautiful colors deepen when it engorges with blood during sexual stimulation. 

Labia Minora (Inner Labia)

The labia minora, or the “inner lips”, are located to the inside of the labia majora, in a pattern similar to the inner petals of a flower, through which the “legs” of the sensitive crura run. They are made of permeable mucous membrane, contain sebaceous glands, and are chock full of nerve endings that communicate touch and sensation.  

The lips of the labia minor play a beneficial role in helping to keep bacteria out of the vestibule. They are directly attached to the clitoral hood at the fourchette, and movement of the lips can cause varying degrees of pleasurable stimulation to the clitoris. Contrary to  myth, this indirect form of clitoral stimulation often does not result in orgasm. 

Labia minora vary a great deal in size, shape and color. They can be pink, violet, red, brown, salmon, lilac, crimson, purple, ebony, peach, or all of the above at once in a gorgeous symphony of color. Getting to know and appreciate the special beauty of your genitals is one of the great pleasures of anatomical self-knowledge!

It's not unusual for one side of the labium to be shaped differently than the other, or to be longer. This lovely asymmetry is part of the character makes each woman’s’ genitals unique and distinctive. 

The Vestibule (Inner Rectangle)

The vestibule is the area between the labia minor that houses and connects the clitoris, urethra and the vaginal opening. 


The fourchette is the place where the lips of the labia  come together at the base of the labia. 


The urethra is located beneath the clitoris. It contains a tube which runs from the bladder to a small aperture called the urethral opening through which urine passes.

The relatively shallow female urethra is susceptible to bacterial infection during sex, and it’s a good habit to urinate after sex to help cleanse the urethral tube. Drinking pure cranberry juice can also help keep the urethral tract healthy. 

Skene’s Glands

Right inside the urinary opening and on the upper wall of the vaginal canal are the paraurethral glands, or Skene’s glands. These are the female equivalent of the male prostate gland. The Skene’s glands drain into the urethra. 


The vagina is the passage from the external female genitalia to the internal reproductive system. The vaginal opening, the entrance to the vaginal canal, is located below the urethra. Most of the sensitive nerves in the canal are located in the first third of the tract. 

The vaginal canal is a curving, muscular passage from the vaginal opening to its top, or fornix. It's shaped like a shallow backward C curving back and up from the vaginal opening. The vaginal canal is remarkably elastic, especially during a woman's fertile years when it can expand many times its normal size during childbirth to allow the passage of a baby. Despite this seeming superpower, the vaginal walls are made of delicate mucosal tissue that is susceptible to tearing with rough treatment. Sufficient muscular relaxation, lubrication, and sensitive movement during vaginal penetration are essential to prevent this. 

The vagina has a natural defense system, including an acidic pH balance, resident bacteria that fight off infection, and a self-cleansing function that expels discharge regularly. This cleansing discharge changes color and consistency; pre and post menstrual discharge may be slightly brown, while during ovulation it becomes more mucosal.  

During post-puberty sexual stimulation, the vagina produces a clear or watery lubrication, secreted from the Bartholin’s glands and sweat glands, that protects the vaginal tissue and increases sexual pleasure by reducing friction.  

These secretions signify that the vagina is functioning in a healthy and normal fashion.  “Feminine hygiene” products and douching interfere with this vital process, and can cause dryness, tearing and irritation to the vaginal tissue.  

Inside the vaginal canal you can feel various skin textures and protrusions from intersecting organs. For example, you can feel the spongy G-spot, the bump of the cervix, and at the top of the vaginal canal, the fornix. In some women, varying degrees of a hymen may be felt right inside the vaginal opening. 

The muscles of the vagina are strong, active, and expressive. They can clutch, hold and bear down on an object forcefully, and can propel an object or stream of water quite some distance. But like any other muscles, the vaginal muscles can also lose their strength and tone. They are subject to stretching, tearing, and desensitization through childbirth, sexual assault, or with age or neglect. Exercising the vaginal muscles, along with the connected supportive pubococcygeal (PC) muscles, is as important to the health of your  reproductive organs as regular aerobic exercise is to your heart muscle. 

The inactive vagina can also become shrunken or closed. In some cases, adhesions may build up inside the vagina, causing blockage. This is more likely to occur in women after menopause when the bodies hormonal output decreases, or in women who forgo any vaginal penetration for an extended period. To avoid this, it's a good idea to insert your fingers or a dildo into your vaginal canal on a regular basis to keep the vagina open, toned and elastic. Make sure to use plenty of warm lubrication.

Bartholin’s Glands

The Bartholin's glands are just inside the vaginal opening. They secrete a lubrication that helps prevent friction and tearing during sexual activity in the vaginal canal, contributing significantly to both sexual pleasure and to the health of the vaginal walls.   


The fornix is located at the top of the vaginal canal. During sexual stimulation and orgasm the fornix “tents” upward as the uterus contracts, expanding the vaginal canal.

Women who have had a hysterectomy no longer experience this “tenting” effect because the uterus has been removed. This can feel a bit different, but it does not diminish the pleasure or intensity of orgasm.


The G-spot, or Grafenberg Spot, is an area located roughly two inches inside and in the front wall of the vaginal canal. It is distinguished by it's sensitivity and unique spongy texture/feel. Response to G-spot stimulation varies considerably: for some women it is highly pleasurable, while for others it yields little sensation, or is actually uncomfortable.

Finding the G-spot can take a little exploration. You can locate it through manual stimulation and gentle pressure on the G-spot region. Many women associate G-spot pleasure and orgasm with prolonged and relaxed sexual activity and and report G-spot orgasms to be very intense. On occasion, G-spot orgasm can be accompanied by the release of fluid. The quantity of this fluid can vary, from a teaspoon up to a quart.  


The hymen is a thin, opaque membrane just inside the vaginal canal that stretches over the vaginal opening. Some women are born without a hymen, and others are born with a rare condition in which it is entirely sealed. Most hymens are somewhere in between, with a number of perforations called hymenal orifices. Below are examples of hymenal orifice variations:

Hymenal Pain

The hymen does not contain nerve endings, but sometimes women experience pain and/or bleeding during initial vaginal penetration caused by pressure on the parts of the vaginal opening that the hymen is attached to, and by hymenal micro-tearing or stretching. 

Occasionally the hymen is completely or virtually sealed. This seal can cause a great deal of pain during vaginal penetration, and it may even entirely prevent penetration. Do not force a penis or pleasure object into a vagina with a sealed hymen! As with any intense or persistent pain, bring it to the attention of your doctor. It’s a very simple medical procedure to remove a sealed hymen. 

The Myth of Hymenal Virginity

It is not accurate to associate the presence of pain or bleeding from a ruptured hymen with virginity. Many women are born with little or no hymen, and the hymen itself generally wears away during puberty. 


The cervix is the passageway to the uterus. It connects with the vagina about three-fourths of the way up the vaginal canal. You can feel it with your finger as a small protruding dimple, and see it in a mirror by using a speculum to open the vaginal canal.  

Become familiar with the feel and look of this important place. If you use a diaphragm, contraceptive cup or sponge, you will need to know exactly where the cervix is so that you can place these protective barriers accurately over it, and can make sure that they remain in place during sex. 

Pain can result if the thrusting of a penis, dildo, finger or other object impacts too forcefully against the cervix. The experience of any pain is a message from your body telling you to stop and change what you're doing! Sex should never be painful. Try a different position, or shallower thrusting. 

Remember, any persistent genital pain should be brought to your doctors’ attention. 

Os (External Orifice of the Uterus)


The os is the tiny opening of the cervix. Os is Latin for mouth. The astounding os will dilate from the size of a pin prick to the size of a babies’ body during labor and birth.

Uterus (Womb)

The uterus, or womb, is the muscular organ that houses and nourishes a fertilized egg through prenatal development during the nine months of pregnancy. Shaped like an upside down pear, it’s about three inches long and two inches wide, but will expand many times this size during pregnancy to accommodate embryonic growth. It’s made of an elastic outer muscle called the myometrium, and has a remarkable inner lining called the endometrium, or endometrial lining.  

Every month during the menstrual cycle the ovaries prepare for conception by producing the hormone progesterone, which causes the endometrial lining to increase into a thick substance ideally suited to nourish the developmental needs of a fertilized egg. If conception does not occur, progesterone levels drop, causing the endometrium, along with the unfertilized ovulated egg, to shed. This shedding is the secretory phase of the menstrual cycle, or the menstrual period.  


The two grape-sized ovaries are located on either side of the uterus near the openings of the fallopian tubes. They are attached on one end to an ovarian ligament, and the uterus on the other end. 

The ovaries contain ovum, or unfertilized eggs, each of which is wrapped in a thin follicle of tissue and which produce the hormones estrogen, progesterone, and testosterone. (Estrogen is also produced by fat tissue, and testosterone is also produced by adrenal glands). The approximately 200,000 eggs stored in each ovary are present at birth; no more eggs are produced during a woman’s lifetime. 

Each month during the menstrual cycle, one or more ovum is developed inside its special ovarian follicle, or pouch, and then released during ovulation. Eggs are typically released once a month and one at a time, but sometimes more than one egg may be released, and women may ovulate more than once during a menstrual cycle.

The estrogen and progesterone secreted by the ovaries help maintain healthy organ function by keeping the sexual organs flexible and viable and the vaginal wall elastic and full. During the monthly fertility cycle, progestin causes the nutrient-rich endometrial lining of the uterus to build up in preparation for pregnancy. Estrogen and progesterone also influence the development of embryonic female or male sex characteristics. Testosterone is an important hormone in creating both female and male sexual desire.  

Fallopian Tubes (Oviducts)

The fallopian tubes, or oviducts, are the conduit through which ovarian eggs travel from the ovaries to the uterus. When the ovaries releases an egg, delicate little tendril-like structures called fimbrae at the opening of the fallopian tubes grasp it and sweep the egg into the tubes, where tiny hair-like structures called cilia help propel the egg down to the uterus.   

Pubococcygeal Muscles (PC Muscles)

The PC muscles surround and integrally support the vagina and help hold the uterus in place.  They are crucial to the wellbeing of the sexual and reproductive system in multiple ways.  

When the vaginal muscles hold or grasp a penis or pleasure object, these muscles play a large part in the action. Keeping them healthy and toned enhances sexual sensation. 

The PC muscles also contribute to safeguarding the internal placement of the uterus and the reproductive organs. If these muscles grow weak or lax, the uterus can eventually slip out of place and into the vaginal canal, causing complications that may require corrective surgery, including hysterectomy. Keeping these muscles strong helps avert this serious health risk. 

The easiest way to locate the PC muscles is by squeezing them to stop your urine stream. Practice a pattern of stopping your urine flow and then releasing it repeatedly, until you have a clear feel for the muscles you’re using. 

You can also find the PC muscles by gently inserting a lubricated finger into your vaginal canal, and using the same muscles that you would use to stop your urine flow to gasp your finger.  

Once you’ve located your PC muscles, practice tightening and releasing these muscles on a regular basis at varied paces, working and strengthening them to a vibrant tone.  Do fifty repetitions at a moderate pace, then fifty medium contractions, and then fifty fast contractions. Make these repetitions part of your daily routine while you brush your teeth, sit on the bus, or eat breakfast. 

Vaginal “barbells” or weights designed to fit the natural curve of the vagina and build strength and tone in the PC muscles are also available from your gynecologist, and at good sex aid stores. Good Vibrations, Smitten Kitten, A Woman’s Touch, and Betty Dodson have kegel exercise equipment for women online. See Sex Education Resources.


The perineum is the stretch of skin between the vagina and the anus. It is seamed by the Raphe. 

AnusThe anus is the opening to the rectum. Lots of nerve-endings cluster at the anus, making it very sensitive to stimulation. 


Beyond the anus is the rectum, a long tube which extends from the intestines. Digested food, or excrement, is expelled from the body through the rectum. A strong muscle column called the sphincter rings the beginning of the rectal passageway. This protective muscle band helps prevent fecal matter from involuntarily escaping the rectum. 

The rectum is made of porous, relatively thin mucosal tissue.  It does not have the elasticity or self-lubricating facility of the vagina, which makes it quite susceptible to tearing during anal/rectal penetration. A specialized “anal lubricant” should be used during rectal penetration that is thick enough to lubricate and buffer the fragile rectal tissue, and care should be taken not to thrust roughly into the rectum. Tearing of the rectum may create sepsis, a very dangerous contamination of fecal matter in the internal system, and it also greatly increases the risk of STI infection. 


Chest wall
 2. Pectoralis muscles

 3. Lobules
 4. Nipple
 5. Areola
 6. Milk duct
 7. Fatty tissue
 8. Skin

The breast and especially the nipples are full of sensitive nerve endings, and many women find them  to be an intense erogenous zone. They come in a variety of sizes and shapes, depending on the amount of glandular tissue, mammary gland (milk-glands) and/or lobules, connective tissue, and fatty tissue in them, as well as hormones present in the body and individual body structure.

The breasts are attached to the pectoral muscles and the rib cage by ligaments. They contain no muscle themselves. Between the ligaments are pockets of fat containing mammary glands which lead to lactiferous ducts, or milk ducts. The milk ducts are located behind the areola, the dark area of skin that surrounds the nipple. The nipples are connected to milk ducts by small openings which allow an infant to access the milk ducts. The areola also contains the Montgomery glands, which are sometimes visible in the appearance of little concentric bumps around the edge of the areola.


Male Sexual and Reproductive Anatomy


The Mons is the slightly curved area above the penis which is covered by pubic hair. 



Penile glans (head)                                    Glans with foreskin

Coronal Ridge                                             Frenelum 




The scrotum is a soft, protective sack that contains the testes and the epididymis. It is located behind the penis. Individual scrotums vary in length, color, and texture. Like women’s labia, one side often hangs down lower than the other (commonly the left), creating distinctive and beautiful designs that differ with every man’s unique body.  

Testicles (Testes)

The testicles are two almond-sized organs contained within the protective sack of the scrotum. They are primarily responsible for producing testosterone in men. During puberty, hormonal signals cause the seminiferous tubules inside of the testicles to begin producing sperm.  

The testes are slightly cooler in temperature than the rest of the body, in order to provide a comfortable environment for sperm. During sex, physical exertion, cold, or duress, the testes draw in close to the body.



Sperm are the male reproductive cells that contain one half of the chromosomes and genetic material that form an individual during conception. The male reproductive system is intricately fashioned to conduct sperm into the female reproductive system, where it can fertilize an egg and initiate conception. The total volume of sperm in each ejaculation ranges from 120,000,000 to 600,000,000. Men begin producing sperm at puberty. As men age they gradually produce less sperm, but will continue some sperm production for their entire lives. 

Semen (Ejaculate)

To form semen, or ejaculate fluid, the prostate gland, seminal vesicles, vas deferens and the Cowper’s gland release fluids which blend together with sperm.  The resulting semen is composed of about 2 to 5% sperm, 30% prostate fluid, and a 65% mixture of fluid from the Cowper’s glands, the vas deferens, and the seminal vesicles. 

Semen is propelled from the penile opening during ejaculation by muscular contractions. When ejaculation occurs inside or near the vagina, this energetic ejection helps carry sperm into the female reproductive system. 


The epididymis is a tube-like structure in back of each testicle. After initial production in the testicles, the sperm move into the epididymis where they will either be expelled during ejaculation, or stored for up to six weeks before dissipating.  

Vas Deferens

The vas deferens is made of two long tube-like structures about 20 inches in length which are connected to the epididymis on one end and to the ejaculatory duct on the other. During ejaculation, muscular contractions and the movements of cilia (small hair-like structures) help sperm to travel from the epididymis through one of the vas deferens to the ejaculatory ducts, where the sperm collect prior to being expelled in ejaculate fluid. 

Ejaculatory Ducts

The two ejaculatory ducts are formed by the union of the vas deferens with the duct of the seminal vesicles. They pass through the prostate and open into the urethra. The ejaculatory ducts cause the reflex action of ejaculation. 

Seminal Vesicles

Located between the urethra and the vas deferens at the ejaculatory duct, the seminal vesicles are two small sacs that produce an alkaline fluid which helps neutralize the acidic environment of the vagina, and contain a fructose substance that nourishes sperm.  

Spermatic Cord

The spermatic cord is a bundle of nerves and blood vessels that serve the testicles, the vas deferens, and the epididymis. 

Cowper’s Glands (Bulbourethral Glans)

The Cowper’s glands are two pea-sized glands located at the base of the penis. When sexually stimulated, they secrete an alkaline fluid which helps protect sperm during ejaculation by neutralizing any urethric acid left in the urethral tube, because sperm does not thrive in an acidic environment. It also helps neutralize the acidic environment of the vaginal canal. During ejaculation, fluid from the Cowper’s glands contributes about 5% of semen’s fluid content. 

The Cowper’s glands sometimes release pre-ejaculate fluid that contains small amounts of sperm. This is why any penile - vaginal contact or insertion may cause pregnancy, even without erection or ejaculation.  

Prostate Gland (“Male G-Spot”)

The prostate gland is a chestnut-shaped gland about one and a half inches around. It surrounds a small part of the urethra, below the bladder.  During ejaculation the prostate secretes about 30% of seminal fluid volume. The seminal vesicles also secrete an important fluid into the urethra at the prostate. 

The prostate is sometimes called the “male G-spot” because many men find stimulation of the prostrate intensely pleasurable. It is easiest to feel by gently inserting a well lubricated finger into your rectum and feeling for this chestnut-shaped organ through the front of the rectal passage.  

 Is My Penis Too Curved?

Most penises' have a natural curve to them in one direction or another. Unless this curve is extreme and causes discomfort or pain during sex, it’s nothing to worry about; in fact it may be useful during vaginal-penile sex, because the vagina also curves, and a curved penis fits more naturally to the shape of the vaginal canal.


See Body Image 


The penis varies widely in size, shape, coloration, and texture from individual to individual. A wondrous organ that plays a key role in pleasure, intimacy, and the creation of life, it's made from the interdependent workings of an intricate inner structure that include the urethral meatus, penile glans, foreskin, Tysons glands, coronal ridge, frenulum, raphe, and shaft. 

Urethral Meatus (Penile Opening)

The urethral meatus is the opening of the urethral tube at the tip of the penis through which semen and urine pass.  

Penile Glans (Head)

The penile glans or head forms a smooth, bulbous shape at the top of the penile shaft. Chock-full of nerve endings, it is extremely sensitive to stimulation. The glans is filled with spongy tissue that engorges with blood during sexual arousal, darkening its color and enlarging it.  


In uncircumcised men the penile glans is covered by a protective foreskin that retracts during erection. The foreskin protects the penile gland from rubbing and irritation during its resting, or non-aroused state, which helps maintain its tactile sensitivity. It is attached to the penis in two ways: at the very base of the penis, and all along

its length by the frenar band, which extends from the frenulum and runs in a long loop within the foreskin.  

Tysons Glands and Smegma

The foreskin contains the Tysons glands which secrete a fluid that, together with prostate fluid and shed skin cells, forms a thick, white substance called Smegma that builds up under the foreskin. Because Smegma is an ideal medium for bacterial growth, the foreskin should be gently retracted and any Smegma cleaned off with mild, unscented soap and water on a regular basis.  

Coronal Ridge (Corona)

The coronal ridge is the elegant crown, or ridge of tissue, around the head of the penis. It is full of highly sensitive nerve endings and spongy tissue that engorges with blood, expanding during sexual stimulation.  

Frenulum/ Frenum

The frenulum is a patch of skin located on the bottom side of the penis.  Like the coronal ridge and penile glans, it is highly sensitive to touch. 


The Raphe is a ridge or seam in the skin, made of gonadal tissue, which runs along the bottom of the penis and intersects the scrotum. 

Penile Shaft

The penile shaft is primarily made up of three parts: the corpus spongiosum, the corpus cavernosa, and the urethral tube. 

Corpus Spongiosum

The corpus spongiosum is one of three cylindrical shafts that run the length of the penile shaft. Located on the bottom of the penis, the corpus spongiosum is filled with spongy tissue and small blood vessels that engorge with blood during erection. A thin membrane holds the blood inside the cylinder and contributes to the rigidity of the penis during erection. The urethra runs through the center of this cylinder, the passageway for semen and urine. 

Corpus Cavernosa

The corpus cavernosa is made of two cylinders located next to each other, on top of the penis. Like the corpus spongiosum, they are full of many small blood vessels and spongy tissue which swell as they fill with blood during sexual stimulation, and a thin membrane that holds the blood inside these cylinders during arousal, implementing penile erection. 

Urethra (Urethral Tube)

The urethra is tube that runs the length of the corpus spongiosum. It connects to the bladder and the male reproductive system, secreting urine, pre-ejaculate fluid, and semen. During ejaculation, a muscular valve called the urinary sphincter located at the opening of the bladder closes, preventing urine from being released into the urethra and mixing with seminal fluid.  


The perineum is the smooth stretch of skin between the scrotum and anus. 


The anus is the entrance to the rectum. Lots of nerve-endings cluster at the anus, making it very sensitive to stimulation. 


Beyond the anal opening is the rectum or rectal passage, which is connected to the intestines. It is the passage through which excrement is expelled from the body. A strong muscle called the sphincter rings the beginning of the rectal passageway and keeps the anus closed to prevent fecal matter from escaping the rectum, unless a bowel movement is occurring. 

The rectum is made of very porous, relatively thin mucosal tissue and does not have the elasticity or self-lubricating facility of the vagina, making it susceptible to tearing during rectal penetration. A special lubricant should be used during rectal penetration which is thick enough to lubricate and buffer the fragile rectal tissue, and care should be taken not to thrust roughly into the rectum. Tearing may create sepsis, a dangerous

contamination of fecal matter released into the body, and tearing also greatly increases the risk of STI infection. Be gentle during rectal sexual play. 

Rectal penetration is often particularly pleasurable to men because the highly sensitive prostate gland can be stimulated through the rectum.  

Pubococcygeal Muscles (PC Muscles)

The PC muscles surround and integrally support the genitals.  They are crucial to the wellbeing of the sexual and reproductive system in multiple ways. If they grow weak or lax, hernia may occur, causing complications that may require corrective surgery. Keeping these muscles strong helps avert this serious health risk. It also enhances sexual pleasure. 

The simplest way to locate the PC muscles is to squeeze them by stopping your stream of urine. Practice a pattern of stopping the flow and then releasing it over and over until you have a clear sense of the muscles you’re using to achieve this. Then you can practice tightening and releasing these muscles on a regular basis anytime, at different paces, working and strengthening them to a vibrant tone. Try doing fifty repetitions at a moderate pace, then a medium pace, then fast. Incorporate this practice into a daily routine while you brush your teeth, sit on the bus, or eat breakfast. 

Intersex Sexual and Reproductive Systems

Some people are born with a combination of female and male sexual and reproductive anatomy and physiology. This is a normal variation in the human chromosomal structure. They may identify with one sex to varying degrees, or with both sexes. They may opt not identify with the concept of gender at all, but choose simply to see themself as the unique human being they are. Any of these perceptions are completely valid.


Intersex genitalia

Breast development in Klinefelter's Syndrome

Neck development in Turner's Syndrome
Individuals medically classified as intersex are called hermaphrodites - people born with a full set of both female and male sex organs. People born as full hermaphrodites often have difficulty with fertility, although there are exceptions. 

Other intersex people are born with varying degrees of mixed sex chromosomal and hormonal variations.

 Examples of Chromosomal Variations: 

Klinefelter's Syndrome

Men with Klinefelter's syndrome have 47 chromosomes rather than 46, with a double XX sex chromosome. This gives them the chromosomal pattern 47XXY. Approximately one in every 400 to 700 men has some degree of Klinefelter's syndrome.  

Frequently men with Klinefelter's show no outward evidence of its effects, but in some cases Klinefelter's can have a pronounced effect on sexual development, causing small testicles, growth of breast tissue, and sparse beard growth. Men with Klinefelter’s may produce less testosterone than other men, and will probably not produce sperm.  

For young men at puberty whose appearance is impacted by Klinefelter's in a manner that makes them uncomfortable, testosterone injections may be an option. These shots can help "masculinize” appearances by increasing body hair and other male sex traits, as well as increasing sexual interest and erectile ability. Testosterone injections will not make the testicles produce sperm. 

Turner's Syndrome

Women with Turner's syndrome have 45 chromosomes, rather than 46. The absent chromosome is one of the female X sex chromosomes, giving them the chromosomal pattern45X or 45X0. About one in every 2500 women have Turner's syndrome.

Women with Turner's syndrome frequently lack one or both ovaries, or have only streaks of ovarian tissue, and can rarely produce eggs or female hormones. Without ovaries or eggs, pregnancy is not possible. Women with Turner's also may not develop breasts, or begin their menstrual cycle, unless they take the hormones estrogen and progestin. Many, but not all, are of short stature, and some may have defects of the heart, kidney, or ears that require medical attention.

Speck Syndrome

Men with Speck syndrome have an extra Y chromosome, giving them the chromosomal pattern 47XYY. Some men with Speck syndrome have low sperm production and, more rarely, malformation of the testicles, but many are fertile. Physical findings also indicate that some men with Speck syndrome may be taller than average. 

AIS and 5ARD

AIS (Androgen Insensitivity Syndrome) and 5ARD (five-alpha-reductase deficiency) occur when a 46XY person’s body does not respond to androgens, the hormones responsible for “masculinizing” sex traits. 

There are two types of AIS: Complete AIS (CASI) and Partial AIS (PAIS). People with CIAS do not respond to androgens at all. They often have testes with external female genitals. People with PIAS respond partially to androgens, in varying degrees. They have testes and a range of body types, and genitals that may differ in look and function from the typical XX or XY genitals.      

See Intersex for more insight and information. 

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