The Penis

The penis is the male organ of copulation. Its average dimensions length and diameter in flaccid and erect states are intentionally omitted as size conscious males will immediately measure themselves and feel inadequate if they happen to be smaller than the average size. The penis consists of three cylinders of erectile tissue, the two CORPORA CAVERNOSA which lie adjacent to each other and a third mass, the CORPUS SPONGIOSUM which lies beneath them. The corpus spongiosum contains the urethra. and is enlarged to form the tip or GLANS PENIS. At the root of the penis, the two corpora cavernosa are attached to the pelvic bones. All the three cylinders are enclosed in a fibrous covering, which is surrounded by the skin of the penis. Nature has partitioned off the cavernous cylinders into innumerable small compartments cavernous spaces like tiny cubicles in a modern office.

Erection of the penis

This entirely reflex vascular phenomenon is brought about in a very simple yet ingenious way. Let us see how this marvel of nature takes place. Each cavernous space resembles a small rubber balloon containing blood, not air. The arteries bring oxygenated blood to the penis, whilst the veins return the blood to the heart. Normally the small arteries entering the rubber balloons (cavernous spaces) remain partially contracted to limit the amount of blood to the penis. But when they dilate for erection, the balloons are filled with blood and get inflated. The veins have valves which prevent the blood from leaving the penis. Just as when air is pumped into a tube, the outer wall of the tyre prevents the tube from over distending and makes it hard, similarly the cavernous spaces fill up with blood and make the penis hard and erect with the fibrous covering acting like the outer wall of the tyre.

Nerve supply of the penis

The penis is richly supplied with nerves which control the blood vessels. It is necessary that you should be familiar with the working of the nervous system before learning about the nerve supply of the penis and how it produces a normal erection and how an imbalance of the nervous mechanism can result in sexual inadequacy.

The vast, uncharted and unknown kingdom of the human body (you probably know more about your car than your body!) is ruled and regulated by two ministers: the External Affairs Minister the Central Nervous System (CNS), which responds and regulates the body to the external environment, and the Home Minister the Autonomic Nervous System (ANS), which looks after law and order in your body, that is, taking care of all the vital functions like regulating heart rate, circulation, digestion and glandular secretions, and, last but very important, erection of the penis and the mechanism of ejaculation.

CENTRAL NERVOUS SYSTEM: The CNS consists of the brain and the spinal cord which have an intimate dual connection through the nerves with the rest of the body and particularly with the genital organs. The brain receives sensory signals and transmits messages to the muscles, for appropriate action. The sensory signals initially play a very important role in sexual arousal.

AUTONOMIC NERVOUS SYSTEM: The ANS is outside the control of the will, and regulates your internal environment. It is also responsible for producing erection or the penis and ejaculation. It functions quietly day after day, whether you are awake or asleep. Normally you are not conscious of your heart beats or the digestion going on in your alimentary tract. The ANS maintains law and order in your body through its own intelligence agencies. Every organ is under its surveillance. The moment it misbehaves (for example, indigestion or a heart attack), it is promptly reported to the boss the central nervous system, for the necessary corrective action. For instance, when an individual suffers from a heart attack, the pain in the chest alerts the CNS to take appropriate action take a sedative or lie in bed or consult a doctor.

The ANS consists of two components, the sympathetic and the parasympathetic.

THE SYMPATHETIC NERVOUS SYSTEM is the accelerator of the human engine, like the accelerator of a car. It is concerned with the instantaneous preparation of the body for defense against external threats. The caveman or the wild beast, when attacked, had two alternatives, depending upon the type of threat visualized by the thinking brain. The animal or man may decide that it is better to run away (he who runs away lives to fight another day), or he may decide to fight it out and perhaps be killed. This is called the FIGHT OR FLIGHT RESPONSE. The body, when mobilized by the sympathetic nervous system, resembles a boxing champion ready for a fight. The muscles become tense and alerted, the heart beats faster to supply more blood to the muscles and the brain, and the breathing becomes more rapid to supply increased oxygen to the blood. (Extra glucose is burnt by the muscles to produce extra energy to fight the opponent or run away). The overheated body combustion is cooled down by excessive sweating.

Modern man stimulates the sympathetic nerve to produce stress. During the stress of a life and death situation, obviously the mechanism of sex is kept in abeyance, as the man has either to fight or run away. It is fitting, therefore, that the sympathetic nerve which produces stress is also responsible for contracting the small arteries in the penis, resulting in blood returning to the body and loss of erection. The sympathetic nerve is also the motor nerve for producing ejaculation.

THE PARASYMPATHETIC NERVOUS SYSTEM brings the body back to its normal relaxed condition and restores vital energy. It is like the brake of a car that brings to a halt the accelerating automobile the human engine. The accelerator and brake of a car are under the conscious control of the driver but, unfortunately, in human beings the autonomic nervous system is not under our conscious control.

The parasympathetic nerves bring about rest, relaxation and recuperation. They are the nerves of pleasure, erection and copulation. The parasympathetic fibres originate in the second and third sacral vertebrae of the spinal cord to form a single nerve on each side called the NERVIERIGENTES. Stimulation of the nervierigentes leads to dilation of arterioles (minute arteries) and filling up of the cavernous spaces with blood, producing erection of the penis.

The penis receives a double nerve supply from the spinal nerves as well as from the autonomic nervous system. The spinal supply conveys the sensations of touch, pain and heat from the skin of the penis to the sensory centre in the brain (thalamus). The pleasant sensations produced by arousal and erection of your penis when your partner caresses your organ are conveyed by the spinal nerves to the brain via the spinal cord. If brief, while stimulation of the parasympathetic (nervierigentes) causes erection, stimulation of the sympathetic nerves (hypogastric) causes ejaculation and subsequent loss of erection, due to contraction of the arterioles and decrease in the blood supply to the penis.

Nervous mechanism of ejaculation

The process of ejaculation is a highly complex mechanism more intricate than erection involving not only the accessory sexual organs (epididymis, ductus deferens, seminal vesicles and prostate), but also the pelvic muscles to propel the semen into the vagina. The sympathetic nerve, where stimulation causes stress and loss of erection, is also responsible for ejaculation.

Let us analyze the complicated Process of ejaculation. Imagine that Explorer XY is on the launching pad ready for a voyage to the planet Venus the vagina of your partner. The countdown now begins... Explorer XY is launched into (her) space. As it zooms to and fro it becomes a beehive of activity, sending innumerable messages to the control tower (the brain) from the vagina the resistance offered by it, the humidity and the temperature. If we now imagine a situation where due to metal fatigue or a short circuit, the rocket blows up, similarly ejaculation is an explosive end to intercourse, a means of propelling the semen into the vagina. The process of ejaculation begins by contractions of the muscular coat of the epididymis, ductus deferens, seminal vesicles and the prostate to propel the semen into the prostatic part of the urethra. The internal urethral orifice is sealed off to prevent voiding of urine or flowing of the semen into the urinary bladder. Powerful contractions of the prostate aided by the pelvic muscles expel the semen into the vagina in six to eight strong squirts. Erection soon dies down and the penis is limp and lifeless for some time and then the process starts all over again.

The male organs of reproduction consist of the two testes suspended by the spermatic cord in the scrotum a wrinkled skin pouch. The testes produce the spermatozoa the male seeds of life, and testosterone the male hormone. The union of a spermatozoon and an ovum starts a new life. The epididymis is a pair of long convoluted tubes connecting each testis to the ductus deferens, which is a continuation of the epididymis. Both the epididymis and the ductus deferens act as a storehouse for sperms. The ductus deferens carry the sperms from the scrotum via the groin into the pelvic cavity where it eventually joins the duct of the seminal vesicles to form the ejaculatory duct. The seminal vesicles are two small pouches located between the urinary bladder and the rectum. They provide additives to the semen like fructose, amino acids and vitamins the semen now becomes vitaminised! The lower end of the seminal vesicles unite with the ductus deferens on each side to form the short ejaculatory ducts one on each side opening into the urethra which serves the dual function of evacuating the urine or the semen. The bulbourethral glands are two small glands, situated on either side of the uretlfra below the prostate gland. Each has a duct which pours its viscid secretion into the urethra to provide lubrication of the penis during intercourse.

The penis is the male organ of sexual expression. It consists of three hollow cylinders of erectile tissue, with the urethra traversing through one of them. All the three cylinders are enclosed in a fibrous covering from which various partitions divide the cylinders into innumerable spaces containing blood. The penis is richly supplied with arteries and veins.

Erection of the penis is produced in an ingenious way. Normally the tiny arteries entering the cavernous spaces are partially contracted to limit the amount of blood to the penis. However, when they dilate for erection, the balloons are filled with blood and get inflated. The veins have valves which prevent the blood from leaving the penis. Just as when air is pumped into a tube, the outer wall of the tyre prevents the tube from over distending and makes it hard, similarly the cavernous spaces fill up with blood and make the penis hard and erect with the fibrous covering acting like the outer wall of the tyre.

The penis is governed by the autonomic nervous system which is not under your conscious control. You can therefore never 'will' an erection. Erection just happens when you are sexually turned on. The parasympathetic nerve from sacral 2 and 3 (nervierigentes) is responsible for erection. The sympathetic nerve is responsible for loss of erection and also for producing ejaculation a complicated process where on receiving signals from the nervous system, the accessory organs of reproduction penetrate the seminal vesicles and the ductus deferens contract, aided by the pelvic muscles, to produce ejaculation. The semen is squirted into the vagina in six to eight strong jets. After ejaculation the erection soon dies down till the sexual batteries are recharged once again.