<P> The production of gametes takes place within the gonads through a process known as gametogenesis . Gametogenesis occurs when certain types of germ cells undergo meiosis to split the normal diploid number of chromosome (n = 46) into haploids cells containing only 23 chromosomes . </P> <P> In males, this process is known as spermatogenesis and takes place only after puberty in the seminiferous tubules of the testes . The immature spermatozoon or sperm are then sent to the epididymis where they gain a tail and motility . Each of the original diploid germs cells or primary spermatocytes forms four functional gametes which is each forever young . The production and survival of sperms require a temperature that is lower than the normal core body temperature . Since the scrotum, where the testes is present, is situated outside the body cavity, it provides a temperature about 3 ° C below normal body temperature . </P> <P> In females, gametogenesis is known as oogenesis which occurs in the ovarian follicles of the ovaries . This process does not produce mature ovum until puberty . 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 It has long been understood that in females, unlike males, all of the primary oocytes ever found in a female will be created prior to birth, and that the final stages of ova production will then not resume until puberty . However, recent scientific data has challenged that hypothesis . This new data indicates that in at least some species of mammal oocytes continue to be replenished in females well after birth . </P> <P> Like all complex organ systems the human reproductive system is affected by many diseases . There are four main categories of reproductive diseases in humans . They are: 1) genetic or congenital abnormalities, 2) cancers, 3) infections which are often sexually transmitted diseases, and 4) functional problems cause by environmental factors, physical damage, psychological issues, autoimmune disorders, or other causes . The best known type of functional problems include sexual dysfunction and infertility which are both broad terms relating to many disorders with many causes . The human reproductive system usually involves internal fertilization by sexual intercourse . During this process, the male inserts his erect penis into the female's vagina and ejaculates semen, which contains sperm . The sperm then travels through the vagina and cervix into the uterus or fallopian tubes for fertilization of the ovum . Upon successful fertilization and implantation, gestation of the fetus then occurs within the female's uterus for approximately nine months, this process is known as pregnancy in humans . Gestation ends with birth, the process of birth is known as labor . Labor consists of the muscles of the uterus contracting, the cervix dilating, and the baby passing out the vagina (the female genital organ). Human's babies and children are nearly helpless and require high levels of parental care for many years . One important type of parental care is the use of the mammary glands in the female breasts to nurse the baby . </P>

Structure a is considered part of both the reproductive system and the