All living things, including humans, reproduce. Since all living things eventually die, new creatures of the same kind must constantly be born to perpetuate a particular species. In the reproductive process, two kinds of sex cells, or gametes, are involved- the male gamete or the sperm and the female gamete or the egg. Both these gametes meet in the female's reproductive system to create a new individual. The male reproductive system is essential to the perpetuation of life. The female is dependent on the male for Fertilization of her egg, even though it is she who carries the offspring through pregnancy and childbirth. So let us see what the male reproductive system comprises of.

The male reproductive system is composed of several distinct organs. It can be easily categorized into internal and external structures.

EXTERNAL STRUCTURE

The external structures of the male reproductive system are those that are located outside of the man’s body. They are:

Penis Scrotum Testicles

PENIS It is the male copulatory organ. It is cylindrical pendant organ located in front of the scrotum. The body of the Penis is cylindrical in shape and consists of three internal chambers. These chambers are made up of special, sponge-like erectile tissue. This tissue contains thousands of large spaces that fill with blood when the man is sexually aroused. As the Penis gets filled 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 size during an erection. The longest part of the penis is the shaft, at the end of which is the head, or glans penis. A loose fold of skin, called the prepuce, or foreskin, covers the glans Penis. Inside the penis, there are tubes that transport semen and urine. SCROTUM The scrotum is the loose pouch-like sac of skin that hangs behind the penis. It contains the testicles (also called Testes), as well as many nerves and Blood vessels. The scrotum has a protective function and acts as a climate control system for the Testes. Before birth, the developing testes descend from the abdomen into the scrotum. Successful descent is essential for fertility as a cooler temperature in the scrotum is necessary for good sperm production and proper testicular functioning. In humans, this location seems important by keeping the testis 2 to 3 degrees below normal body temperature. Special Muscles in the wall of the scrotum, called cremasteric muscles, allow it to contract and relax, moving the testicles closer to the body for warmth and protection or farther away from the body to cool the temperature. TESTES The Testes (testis, singular) are a pair of oval-shaped glands. They measure about 5 cm long and 3 cm in diameter and are suspended in the scrotum. The male gonads, Testes, or testicles, begin their development high in the abdominal cavity, near the kidneys. During the last two months before birth, or shortly after birth, they descend into the scrotum. Most men have two testes. The testes are the main male reproductive organ and are crucial for the normal functioning of the male reproductive system. The testis has two related but separate roles:

Production of sperm; Production of the male sex hormone, testosterone.

A tough, white fibrous connective tissue capsule, the tunica albuginea, surrounds each testis. There are about 250 lobules in each testis. Each lobule contains a number of small, tightly packed, fine tubes called seminiferous tubules in which sperm are produced. Special cells present in these seminiferous tubules, called cells of leydig produce the male sex hormone, testosterone.

INTERNAL STRUCTURE

The internal organs of the male reproductive system include the following:

Epididymis Vas deferens Ejaculatory ducts Urethra Seminal vesicle Prostate gland Bulbourethral glands

EPIDIDYMIS The epididymis is a long, coiled tube that rests on the backside of each testicle. Sperm leave the Testes through a series of efferent ducts that enter the epididymis. Each epididymis is a long (about 6 meters) tube that is tightly coiled. When the sperm leave the Testes, they are immature and incapable of fertilizing ova. They complete their maturation process and become fertile as they move through the epididymis. Mature sperm are stored in the lower portion, or tail, of the epididymis. VAS DEFERENS It is also called ductus deferens. The vas deferens is a long, fibromuscular tube that is continuous with the epididymis. It begins at the bottom (tail) of the epididymis. Just before it reaches the Prostate gland, each ductus deferens enlarges to form an ampulla. Sperms are stored in the proximal portion of the ductus deferens, which is a component of the spermatic cord. The vas deferens transports mature sperm to the Urethra in preparation for ejaculation. During sexual arousal, contractions force the sperm into the vas deferens. EJACULATORY DUCTS These are formed by the fusion of the vas deferens and the seminal vesicles. The ejaculatory ducts empty into the urethra. During ejaculation, semen passes through them. Hence once the sperma are produced, they travel through epididymis, and then through vas deferens, which then joins the seminal vesicles to form the Ejaculatory Duct. 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 expelling (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 VESICLE 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 and helps with the sperms’ motility (ability to move). The fluid of the seminal vesicles makes up most of the volume of a man’s ejaculatory fluid, or ejaculate. PROSTATE GLAND It is a dense structure that is located just below the Urinary bladder. It is about the size of a walnut and encircles the Urethra as it leaves the Urinary bladder. The Prostate gland contributes additional fluid to the ejaculate. Numerous short ducts from the substance of the Prostate gland empty into the prostatic Urethra. The secretions of the prostate are thin, milk colored, and alkaline. 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 The bulbourethral glands are also known as Cowper’s glands. They are pea-sized structures located on the sides of the urethra just below the prostate gland. The bulbourethral glands secrete an alkaline mucus-like fluid. This clear, slippery fluid 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. It also provides some lubrication for the tip of the Penis during intercourse.

The organs of the male reproductive system are specialized for the following functions:

The primary function of the male reproductive system is to produce, maintain and transport sperm in their protective fluid called semen. To discharge sperm within the female reproductive tract To produce and secrete male sex hormone, testosterone.

The entire male reproductive system is dependent on hormones, which are chemicals that stimulate or regulate the activity of cells or organs. The primary hormones involved in the functioning of the male reproductive system are follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone. FSH and LH are produced by the pituitary gland located at the base of the brain. FSH is necessary for sperm production (spermatogenesis), and LH stimulates the production of testosterone, which is necessary to continue the process of spermatogenesis. Testosterone is again plays a very important role. It helps in the development of male characteristics, including muscle mass and strength, fat distribution, bone mass and sex drive.

Cryptorchidism Benign prostatic hypertrophy Cancer of the prostate Prostatitis Epididymitis Testicular cancer Impotence Infertility Inguinal Hernia Hydrocele Premature Ejaculation Hypospadias Epispadias Priapism Phimosis