| Info: Human Organ Systems – Reproductive System (Ovaries, Fallopian Tubes, Uterus, Vagina, Mammary Glands, Testes, Vas Deferens, Seminal Vesicles, Prostate and Penis) Reproductive System 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 chromosomes in humans (n=46) into haploids cells containing only 23 chromosomes. 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 capable of fertilization. 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.
The development of the reproductive system and urinary systems are closely tied in the development of the human foetus. Despite the differences between the adult male and female reproductive system, there are a number of homologous structures shared between them due to their common origins within the foetus. Both organ systems are derived from the intermediate mesoderm. The three main foetal precursors of the reproductive organs are the Wolffian duct, Müllerian ducts, and the gonad. Endocrine hormones are a well known and critical controlling factor in the normal differentiation of the reproductive system. The Wolffian duct forms the epididymis, vas deferens, ductus deferens, ejaculatory duct, and seminal vesicle in the male reproductive system and essentially disappears in the female reproductive system. For the Müllerian Duct this process is reversed as it essentially disappears in the male reproductive system and forms the fallopian tubes, uterus, and vagina in the female system. In both sexes the gonad goes on to form the testes and ovaries, because they are derived from the same undeveloped structure they are considered homologous organs. There are a number of other homologous structures shared between male and female reproductive systems. However, despite the similarity in function of the female fallopian tubes and the male epididymis and vas deferens, they are not homologous but rather analogous structures as they arise from different foetal structures 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. Specific reproductive diseases are often symptoms of other diseases and disorders, or have multiple, or unknown causes making them difficult to classify. Examples of unclassifiable disorders include Peyronie's disease in males and endometriosis in females. Many congenial conditions cause reproductive abnormalities but are better known for their other symptoms, these include: Turner syndrome, Klinefelter's syndrome, Cystic fibrosis, and Bloom syndrome. It is also known that disruption of the endocrine system by certain chemical adversely affects the development of the reproductive system and can cause vaginal cancer. Many other reproductive diseases have also been link to exposure to synthetic and environmental chemicals. Common chemicals with known links to reproductive disorders include: lead, dioxin, styrene, toluene, and pesticides. Ovaries The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in females are homologous to testes in males, in that they are both gonads and endocrine glands. Fallopian Tubes The Fallopian tubes, named after Gabriel Fallopius (Gabriele Falloppio), also known as oviducts, uterine tubes, and salpinges (singular salpinx) are two very fine tubes lined with ciliated epithelia, leading from the ovaries of female mammals into the uterus, via the utero-tubal junction. In non-mammalian vertebrates, the equivalent structures are the oviducts. Uterus The uterus (from Latin "uterus" (plural uteruses or uteri) or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species. It is within the uterus that the foetus develops during gestation, usually developing completely in placental mammals such as humans and partially in marsupials such as kangaroos and opossums. Two uteruses usually form initially in a female foetus, and in placental mammals they may partially or completely fuse into a single uterus depending on the species. In many species with two uteruses, only one is functional. Humans and other higher primates such as chimpanzees, along with horses, usually have a single completely fused uterus, although in some individuals the uteruses may not have completely fused. The term uterus is used consistently within the medical and related professions, while the Germanic derived term womb is also common in everyday usage in the English language. Most animals that lay eggs, such as birds and reptiles, have an oviduct instead of a uterus. In monotremes, mammals which lay eggs and include the platypus, either the term uterus or oviduct is used to describe the same organ, but the egg does not develop a placenta within the mother and thus does not receive further nourishment after formation and fertilization. Marsupials have two uteruses, each of which connect to a lateral vagina and which both use a third, middle "vagina" which functions as the birth canal. Marsupial embryos form a choriovitelline "placenta" (which can be thought of as something between a monotreme egg and a "true" placenta), in which the egg's yolk sac supplies a large part of the embryo's nutrition but also attaches to the uterine wall and takes nutrients from the mother's bloodstream. Vagina The vagina (from Latin vagĭna, literally "sheath" or "scabbard") is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the oviduct. The Latinate plural "vaginae" is rarely used in English. The word vagina is quite often incorrectly used to refer to the vulva or female genitals generally; strictly speaking, the vagina is a specific internal structure. Mammary Glands A mammary gland is an organ in mammals that produces milk to feed young offspring. It is an exocrine gland that is an enlarged and modified sweat gland, and gives mammals their name. In ruminants such as cows, goats, and deer, the mammary glands are contained in their udders. The mammary glands of other mammals that have more than two breasts, such as dogs and cats, are sometimes called dugs. Testes The testicle (from Latin testiculus, diminutive of testis, meaning "witness" [of virility], plural testes) is the male generative gland in animals. Vas Deferens The vas deferens (plural: vasa deferentia), also called ductus deferens, (Latin: "carrying-away vessel"; plural: ductus deferentes), is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation. Seminal Vesicles The seminal vesicles (glandulae vesiculosae) or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals. Prostate The prostate (from Greek - prostates, literally "one who stands before", "protector", "guardian") is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals. In 2002, female paraurethral glands, or Skene's glands, were officially renamed the female prostate by the Federative International Committee on Anatomical Terminology.
The prostate differs considerably among species anatomically, chemically, and physiologically. Penis The penis (plural penises, penes) is a biological feature of male animals including both vertebrates and invertebrates. It is a reproductive, intromittent organ that additionally serves as the urinal duct in placental mammals. |
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