Monday, August 19, 2019
Artificial insemination :: essays research papers fc
Artificial insemination is the injection of SEMEN into the vagina by instrumental means. The first artificial inseminations of viviparous (live-bearing) animals were performed by the 18th-century Italian physiologist Lazzaro Spallanzani, who proved that the male contribution to reproduction resided in the semen, although he did not recognize spermatozoa as the fertilizing agents. Pioneering work in the artificial insemination of dairy and beef animals was done in Russia about the time of the Revolutions of 1917. By the 1930s it was being practiced throughout Europe and the United States. The principal advantage of artificial insemination over natural breeding is that a single male of superior genetic quality can be used to impregnate thousands of females, thereby improving herds and increasing dairy and meat production. With artificial insemination, dairy farmers need not risk the deterioration of their herds from excessive inbreeding, nor incur the expense of maintaining their own bulls. In humans, artificial insemination is used to achieve pregnancy when an anatomical impediment prevents direct fertilization. When the male is sterile, semen is collected from an anonymous donor who is known by the physician to have a family history free of genetic disease. The same precautions are taken when, as in recent years, artificial insemination has been used as a means of providing a child to a couple where the woman cannot conceive. In such cases the husband's sperm is used to fertilize a SURROGATE MOTHER, who has volunteered to bear the child, usually for a fee, and to give it up immediately after its birth. At question are the legal aspects of surrogate motherhood as well as unresolved moral and religious issues. In cases where a woman is unable to conceive as a result of defective oviducts, an egg can be removed surgically from her ovary and fertilized "in vitro": in a petri dish under laboratory conditions that simulate the environment inside the oviduct where fertilization normally takes place (see IN VITRO FERTILIZATION). The embryo is then transferred to the woman's uterus to develop normally. Zoo workers are in the process of refining artificial insemination and in vitro fertilization technologies to help breed a rare and endangered species, to replace the expensive and not-always-successful practice of shipping animals around for mating purposes. Importing semen will make it easier to mate rare animals from far-flung zoos, keeping a good amount of variety in the gene pool.