Sex In Human Loving!

Human Sexuality, Loving, Dating, and Relationships


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The penis is a miraculous organ, an anatomical miracle, that alters size and shape, becomes hard or rigid, soft or flaccid, and still manages to eject semen and urine through a single flexible tube. Is there any other human organ which goes through so many shifts of size and has so many functions?

You may well think the penis is one of the most cunningly designed organs in the human body.

The ingenious design starts on the outside and moves in. How does the skin of the penis cope with such expansion and contraction? For a start, it's thinner, more elastic and looser than any other skin on the body - it needs to be, to cope with thrusting as the penis moves in the vagina (and, some would say, to cope with masturbation!).

The glans is smooth and emerges from the foreskin with exquisite sensitivity - ideal for an organ whose function is to give pleasure and, through that pleasure, cause an ejaculation of reproductive fluid. 

A 1986 study discovered that sensory receptors unique to the penis existed in all parts of the organ - the glans, the coronal ridge, and the frenulum: and recall that all three of these areas have the capacity to expand when a man is aroused, which creates a larger area for erotic sensation.

So the penis is a neural hotspot, one with a concentration of nerves which may even have the power to alter brain function. Although nerve density is greater in the face and the hands, and these areas do in fact have bigger centers in the brain which process their nerve impulses.

Dr. Claire C. Yang, coauthor of "Innervation of the Human Glans Penis" (published in the Journal of Urology), suggests that nerve impulses from the penis are so powerful that they may even alter the brain's function: she says that nervous signals from the penis may enhance the brain's ability to process penile stimulation.

The urethra, the tube through which semen and urine are expelled, runs down the center of the penis, from the meatus - the pee-hole - to the bladder.

Obviously its resting length has to increase, to almost double in some cases, as a man gets an erection - from about three inches to six inches or more.

The urethra is surrounded by the corpus spongiosum, and this bundle of tissue is in turn located under the two corpora cavernosa, which sit above them to the left and right of the midline - and the whole mass is enclosed in the fibrous elastic tissue of the tunica albuginea.

The three corpora fill with blood when a man becomes erect, and the two corpora cavernosa go all the way down the shaft and are connected by ligaments to the pubic bone. (In those misguided men who have penile lengthening surgery, these ligaments are cut so that the penis supposedly drops down and appears longer. Sadly, it is also a lot more wobbly when erect, which is why few doctors are prepared to do this very risky surgery.)

The tunica albuginea, the elastic/fibrous tissue around the corpora is only a millimeter or two thick, and although strong, it's not very flexible.

This means that if the penis is put under undue strain, during masturbation or intercourse, it can break - at least, that's what it sounds like if it happens. In fact the injury is more like a tear than a cracked bone. This mostly happens when the woman is in top: she rides up, he slips out of her vagina, she comes down, she lands on his penis and bends it in a way it was never meant to bend.

Although not common, it's a nasty injury and needs immediate medical help. If the right attention is given, within a few hours, the tunica can be surgically repaired in most cases.

We think of ejaculation and orgasm as being the same process, or at least linked so closely that they are effectively the same. But they are not - they are quite separate, and only ejaculation involves the penis. Of course, orgasm is stimulated by the nerve impulses sent from the penis to the brain; it is the ejaculatory reflex of the brain/spinal column axis which controls ejaculation.

Sperm cells produced by the testes wait in the epididymis for an ejaculation, then travel through the two vas deferens - one from each testicle - to the urethra. (A vasectomy cuts these tubes, and this makes a man sterile.) The seminal vesicles meet the vas deferens just before they emerge into the urethra.

The seminal vesicles are small glands which provide sugar and other nutrients needed by the sperm on their journey to the egg. The prostate gland, a walnut size gland which surrounds the base of the urethra, also contributes some essential chemicals to the semen, so enabling the sperm to live long enough to fertilize the egg.

At the point of emission (which men know and love, as the first sign of an inevitable impending ejaculation, the point of ejaculatory inevitability) semen is ejected into the base of the urethra before ejaculation, and the seminal vesicles and prostate simultaneously contract and add their fluids to the mix.

The resulting semen is ejaculated by a number of contractions of the bulbourethral muscle, which surrounds the urethra.

Email   Leighton Mowbray