The reproductive system in male consists of the following organs: a pair of testes, a pair of epididymis, a pair of vasa deferentia, urethra, penis and accessory glands.

Testes

Testes are the male gonads. In an adult male, each testis is approximately 4-5 cm long and about 12 g in weight. Testes are extra-abdominal, that is, present outside the abdomen in a pouch made up of skin and connective tissue called scrotal sac or scrotum that hangs in the region between the legs.

The scrotum acts as a thermoregulator. It helps in maintaining the temperature of testes at about 2-3°C lower than the body temperature. This temperature is suitable for the development of sperms.

Epididymis

It is a long highly coiled tube which remains attached to the testis and lies within the scrotal sac. Epididymis stores spermatozoa (sperms) and serves as a passage for their transport from the testis.

Vas deferens (sperm duct)

Each epididymis continues as vas deferens. It enters the abdominal cavity, passes over the urinary bladder and joins the duct of seminal vesicle to form the ejaculatory duct. The ejaculatory duct opens into the urethra.

Urethra

The urethra in males is about 15-20 cm long and is differentiated into three parts - an anterior prostatic part which passes through the prostate gland; a middle membranous part; and a posterior penile part which passes through the copulatory organ, the penis. Urethra functions as a passage for both semen and urine.

Penis

Penis is a cylindrical, spongy, muscular and a highly vascular (supplied with blood vessels) copulatory organ in males. The urethra runs through it centrally and serves as a common passage for urine and semen. During sexual excitement, the spongy tissue gets filled-up with blood, making it erect and stiff.

Externally, the penis is covered by skin. The tip of the penis is soft and highly sensitive. It is called glans penis. It is covered by a loose fold of skin called prepuce which can be retracted.

Accessory Glands

The accessory glands include seminal vesicles, prostate glands and Cowper’s glands.

Seminal vesicles

A pair of seminal vesicles are present at the base of the urinary bladder. The seminal vesicles store sperms that descend from the testis and secrete seminal fluid. The seminal fluid is a viscous fluid which provides nourishment to the sperms. This secretion forms about 40-80 percent of the ejaculate (semen thrown out of the penis).

Prostate gland

Prostrate gland surrounds the first part of the urethra. It secretes an alkaline fluid which is discharged into the urethra. This fluid keeps the sperms alive and helps them to swim vigorously. Secretion of prostrate gland forms about 5-30 percent of the ejaculate.

Cowper’s glands or Bulbo-urethral glands

These are paired glands that lie below the prostate gland and join the urethra at a short distance from that of the prostate gland. Cowper’s glands secrete a white, viscous, alkaline secretion resembling mucous which acts as a lubricant.

Spermatozoa and Semen

The process of formation of sperms is termed Spermatogenesis. The spermatozoa are male gametes produced by the testes. Structurally, human sperm has three main parts - head, neck and tail. The tip of a sperm is covered by a cap-like structure, acrosome, which helps the sperm to penetrate inside the egg during fertilization.

Spermatozoa are immotile when stored in the epididymis but get activated and motile by the secretions from the accessory reproductive glands in males. The secretions of various accessory glands along with sperms form the semen. The sperms are released in millions. In one ejaculation about 200,000,000 (2 × 108) sperms are discharged. Sperms when introduced into the vagina of the female move with the speed of 2 mm/minute in side the body of the female.