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Reproductive Systems
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring. Reproductive System 2001 Body Guide powered by Adam Animals In mammals, the major organs of the reproductive system include the external |
Sex Organs
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, are called the ''primary sex organs''. All others are called ''secondary sex organs'', divided between the external sex organs—the genitals or external genitalia, visible at birth in both sexes—and the internal sex organs. Mosses, ferns, and some similar plants have gametangia for reproductive organs, which are part of the gametophyte. The flowers of flowering plants produce pollen and egg cells, but the sex organs themselves are inside the gametophytes within the pollen and the ovule. Conifer, Coniferous plants likewise produce their sexually reproductive structures within the gametophytes contained within the Conifer cone, cones and pollen. The cones and pollen are not themselves sexual organs. Terminology The ''primary sex organs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. There are two forms of reproduction: asexual and sexual. In asexual reproduction, an organism can reproduce without the involvement of another organism. Asexual reproduction is not limited to single-celled organisms. The cloning of an organism is a form of asexual reproduction. By asexual reproduction, an organism creates a genetically similar or identical copy of itself. The evolution of sexual reproduction is a major puzzle for biologists. The two-fold cost of sexual reproduction is that only 50% of organisms reproduce and organisms only pass on 50% of their genes.John Maynard Smith ''The Evolution of Sex'' 1978. Sexual reproduction typically requires the sexual interaction of two specializ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uterus is a hormone-responsive sex organ that contains glands in its lining that secrete uterine milk for embryonic nourishment. In the human, the lower end of the uterus, is a narrow part known as the isthmus that connects to the cervix, leading to the vagina. The upper end, the body of the uterus, is connected to the fallopian tubes, at the uterine horns, and the rounded part above the openings to the fallopian tubes is the fundus. The connection of the uterine cavity with a fallopian tube is called the uterotubal junction. The fertilized egg is carried to the uterus along the fallopian tube. It will have divided on its journey to form a blastocyst that will implant itself into the lining of the uterus – the endometrium, where it will ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, which are known as spermatozoa, while some red algae and fungi produce non-motile sperm cells, known as spermatia. Flowering plants contain non-motile sperm inside pollen, while some more basal plants like ferns and some gymnosperms have motile sperm. Sperm cells form during the process known as spermatogenesis, which in amniotes ( reptiles and mammals) takes place in the seminiferous tubules of the testes. This process involves the production of several successive sperm cell precursors, starting with spermatogonia, which differentiate into spermatocytes. The spermatocytes then undergo meiosis, reducing their chromosome number by half, which produces spermatids. The spermatids then mature and, in animals, construct a tail, or flagellum, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semen
Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen is produced and originates from the seminal vesicle, which is located in the pelvis. The process that results in the discharge of semen from the urethral orifice is called ejaculation. In humans, seminal fluid contains several components besides spermatozoa: proteolytic and other enzymes as well as fructose are elements of seminal fluid which promote the survival of spermatozoa, and provide a medium through which they can move or "swim". The fluid is designed to be discharged deep into the vagina, so the spermatozoa can pass into the uterus and form a zygote with an egg. Semen is also a form of genetic material. In animals, semen has been collected for cryoconservation. Cryoconservation of animal genetic resources is a practice that call ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ejaculate
Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases, ejaculation occurs because of prostatic disease. Ejaculation may also occur spontaneously during sleep (a nocturnal emission or "wet dream"). ''Anejaculation'' is the condition of being unable to ejaculate. Ejaculation is usually very pleasurable for men; '' dysejaculation'' is an ejaculation that is painful or uncomfortable. Retrograde ejaculation is the condition where semen travels backwards into the bladder rather than out the urethra. Phases Stimulation A usual precursor to ejaculation is the sexual arousal of the male, leading to the erection of the penis, though not every arousal nor erection leads to ejaculation. Penile sexual stimulation during masturbation or vaginal, anal, oral, or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Female
Female (Venus symbol, symbol: ♀) is the sex of an organism that produces the large non-motile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female has larger gametes than a male. Females and males are results of the anisogamous reproduction system, wherein gametes are of different sizes, unlike isogamy where they are the same size. The exact mechanism of female gamete evolution remains unknown. In species that have males and females, Sex-determination system, sex-determination may be based on either sex chromosomes, or environmental conditions. Most female mammals, including female humans, have two X chromosomes. Female characteristics vary between different species with some species having pronounced Secondary sex characteristic, secondary female sex characteristics, such as the presence of pronounced mammary glands in mammals. In humans, the word ''female'' can also be used to refer to gender i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erect Penis
An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, and endocrine factors, and is often associated with sexual arousal or sexual attraction, although erections can also be spontaneous. The shape, angle, and direction of an erection varies considerably between humans. Physiologically, an erection is required for a male to effect vaginal penetration or sexual intercourse and is triggered by the parasympathetic division of the autonomic nervous system, causing the levels of nitric oxide (a vasodilator) to rise in the trabecular arteries and smooth muscle of the penis. The arteries dilate causing the corpora cavernosa of the penis (and to a lesser extent the corpus spongiosum) to fill with blood; simultaneously the ischiocavernosus and bulbospongiosus muscles compress the veins of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Intercourse
Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetration for sexual pleasure or sexual reproduction; dictionary sources state that it especially means this, and scholarly sources over the years agree. See, for example; * * * * * * * * * This is also known as vaginal intercourse or vaginal sex. Other forms of penetrative sexual intercourse include anal sex (penetration of the anus by the penis), oral sex (penetration of the mouth by the penis or oral penetration of the female genitalia), fingering (sexual penetration by the fingers) and penetration by use of a dildo (especially a strap-on dildo). These activities involve physical intimacy between two or more individuals and are usually used among humans solely for physical or emotional pleasure and can contribute to human bonding. Ther ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Fertilization
Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For internal fertilization to happen there needs to be a method for the male to introduce the sperm into the female's reproductive tract. Most taxa that reproduce by internal fertilization are gonochoric. In mammals, reptiles, and certain other groups of animals, this is done by copulation, an intromittent organ being introduced into the vagina or cloaca. In most birds, the cloacal kiss is used, the two animals pressing their cloacas together while transferring sperm. Salamanders, spiders, some insects and some molluscs undertake internal fertilization by transferring a spermatophore, a bundle of sperm, from the male to the female. Following fertilization, the embryos are laid as eggs in oviparous organisms, or continue to develop inside the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Reproductive System
The human reproductive system includes the male reproductive system which functions to produce and deposit sperm; and the female reproductive system which functions to produce egg cells, and to protect and nourish the fetus until birth. Humans have a high level of sexual differentiation. In addition to differences in nearly every reproductive organ, there are numerous differences in typical secondary sex characteristics. Human reproduction usually involves internal fertilization by sexual intercourse. In this process, the male inserts his penis into the female's vagina and ejaculates semen, which contains sperm. A small proportion of the sperm pass through the cervix into the uterus, and then into the Fallopian tubes for fertilization of the ovum. Only one sperm is required to fertilize the ovum. Upon successful fertilization, the fertilized ovum, or zygote, travels out of the fallopian tube and into the uterus, where it implants in the uterine wall. This marks the beginning of ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intromittent Organ
An intromittent organ is any external organ of a male organism that is specialized to deliver sperm during copulation. Intromittent organs are found most often in terrestrial species, as most non-mammalian aquatic species fertilize their eggs externally, although there are exceptions. For many species in the animal kingdom, the male intromittent organ is a hallmark characteristic of internal fertilization. Species with intromittent organs Invertebrates Molluscs Male cephalopods have a specialized arm, the hectocotylus, which is inserted into the female's mantle cavity to deliver a spermatophore during copulation. In some species, the hectocotylus breaks off inside the female's mantle cavity; in others, it can be used repeatedly to copulate with different females. Arachnids In spiders the intromittent organs are the male pedipalps, even though these are not primarily sexual organs, but serve as indirect mating organs; in the male the pedipalps have hollow, clubbed tips, oft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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