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Male Sexual Anatomy

External Genitalia

Penis –This executive organ of sexuality is made up of glans, shaft and root. It is traversed by the penile urethra, which serves as a passageway for both urine and semen. The urethra is surrounded by three parallel tubes of erectile tissue which is made up like a sponge with innumerable spaces. When the erectile tissue becomes engorged with blood the penis becomes distended, rigid and erect.
Glans –The glans is the tip of the penis and is covered by the protective fold of skin, known as the foreskin or prepuce. The rite of circumcision – surgical removal of the foreskin-has been practiced by Jews and Moslems and by many other peoples throughout the world. The origin of the operation is related to old ideas that the normal secretions which accumulate under the foreskin if it is not retracted and washed regularly were unhygienic.

In some races the operation is carried out at puberty to signify the boy’s emergence into manhood. Circumcision is rarely indicated on medical grounds although it is still widely practiced in many countries such as Australia. It is not true that the circumcised penis is less sensitive and that the circumcised male is more likely to suffer premature ejaculation; during intercourse the foreskin is retracted and stays this way as long as the penis is in the vagina. n Shaft The shaft of the penis varies in length and diameter, and connects the glans to the root. Some men are very preoccupied with penile size, but there is a good deal of normal variation.

Average penises range in length between seven and eleven cm (three to four-and-a-half ins), in the flaccid state and fourteen to eighteen cm (five to seven-and-a-half ins), in the erect state. This variation in size is not usually related to the size of the man, i.e., small men do not necessarily have small penises and large men do not necessarily have large penises. The fact that a small flaccid penis gets relatively bigger than a large flaccid penis means that the size when erect cannot be gauged by the size when the penis is in a flaccid condition.

Root – The root of the penis is situated where the glans joins the body. It is composed of erectile tissue, continuous with that of the shaft, and is covered by muscles which contract strongly at the time of orgasm and cause the ejaculation of semen from the external opening of the urethra at the tip of the penis.

Scrotum – This is the pouch of skin which hangs down from the root of the penis. It is divided into two compartments, each of which contains a testis. The scrotum has an important part to play in keeping the temperature of the testes constant, slightly below normal body temperature. In cold weather, muscle fibres just below the surface of the scrotal skin contract and make it very wrinkled.

This draws the testes up nearer the body thereby reducing the amount of heat lost. In warmer conditions, the muscles are relaxed, the skin is smoother and the testes hang lower down. It is thought that the temperature of the testes is important in relation to sperm production. If the temperature of the testes becomes too high, for example, if the testes have not descended into the scrotum, or if the man wears too close-fitting underpants, the production of fertile sperm is inhibited.

Testes – The testes, which lie on each side of the scrotum, perform two important functions. They produce sperm and the male hormone testosterone. Testosterone passes directly into the blood stream to exert its action throughout the body. The sperm, which are formed from cells lining a series of tubes, known as the somniferous tubules, then pass down these tubes into collecting tubes, known as the efferent ducts. The ducts then convey them into the epididymis. G Epididymis This is a dilated tube which is loosely attached to the testes from which it receives the efferent ducts. The lowest part of the epididymis is continuous with the vas deferens, a firm cord-like tube, which runs up from the scrotum into the groin and then internally into the pelvic cavity.

Internal Genitalia

Vas deferens – Having started in the scrotum as part of the external genitalia, the vas becomes part of the internal genitalia when it enters the pelvis and joins the prostate gland. As it enters the prostate, it receives the secretions from the separate duct, known as the seminal vesicle. The final ejaculation of semen comprises the sperm from the testes, together with the secretions from the seminal vesicle, prostate and bulbo-urethral glands.

Bulbo-urethral and Prostate glands The pros- ate gland, which is the size of a walnut, surrounds the urethra and is situated just below the bladder.

It contains muscle fibres which contract during sexual activity and squeeze the clear prostatic secretion into the urethra through a number of small ducts. Below the prostate, two pea-sized glands, known as the bulbo-urethral glands, add their secretions to the urethra. Seminal vesicles The two seminal vesicles are situated on either side of the back of the bladder and their ducts pass through the prostate and into the urethra.

It is thought that the secretions of the prostate, seminal vesicles and bulbo-urethral glands play an important part in enhancing sperm motility (their ability to move) and the ability of the sperm to fertilize. In the absence of sexual stimulation, the urethra remains empty except when urine is passed. When sexual stimulation occurs, the penis becomes erect and at the time of male orgasm the prostate muscles contract and squeeze the sperm and glandular secretions into the urethra. The muscles at the root of the penis then contract and the mixture is propelled through the penis and ejaculated through its tip into the vagina.

A cross-section of the testis, showing the somniferous tubules, a mass of convoluted tubes in which the sperm cells are produced. The sperm pass through the efferent ducts to the epididymus.
The sperm travel from the testes to the penis along the vas deferens. The final ejaculation of semen contains sperm cells and secretions from the seminal vesicle, prostate and bulbo-
urethral glands. These secretions are thought to play a part in enhancing sperm motility.