A small proportion of the sperm pass through the cervix into the uterus and then into the fallopian tubes for fertilization of the ovum.

During labor, the uterine muscles contract, and the cervix dilates typically over a period of hours, allowing the infant to pass from the uterus through the vagina.

[3] The vagina meets the outside at the vulva, which is made up of the labia, clitoris and vestibule;[4] during intercourse this area is lubricated by mucus secreted by the Bartholin's glands.

The lining of the uterus, called the endometrium, and unfertilized ova are shed each cycle through the process of menstruation.

These are produced in the testicles, which are housed in the temperature-regulating scrotum; immature sperm then travel to the epididymides for development and storage.

The final category are those used for copulation and deposition of the sperm within the female; these include the penis, urethra, and vas deferens.

[3] Major secondary sexual characteristics include a larger, more muscular stature, deepened voice, facial and body hair, broad shoulders, and the development of an Adam's apple.

This hormone is also responsible for the development of physical characteristics in men, such as facial hair and a deep voice.

Endocrine hormones are a well-known and critical controlling factor in the normal differentiation of the reproductive system.

In both sexes, the gonads go on to form the testes and ovaries; because they are derived from the same undeveloped structure, they are considered homologous organs.

Each of the original diploid germ cells or primary spermatocytes forms four functional gametes, each forever young.

In contrast with males, each of the original diploid germ cells or primary oocytes will form only one mature ovum, and three polar bodies which are not capable of fertilization.

[12] In male germ cells and spermatozoa, and also in female oocytes, special DNA repair mechanism are present that function to maintain the integrity of the genomes that are to be passed on to progeny.