| [pending revision] | [accepted revision] |
Content deleted Content added
m Reverted edits by 41.113.81.203 (talk) (HG) (3.4.12) |
ClueBot NG (talk | contribs) m Reverting possible vandalism by Troller0919 to version by Haley275. Report False Positive? Thanks, ClueBot NG. (4359700) (Bot) |
||
| (26 intermediate revisions by 16 users not shown) | |||
Line 1:
{{Short description|Procreative biological processes of humanity}}
{{pp-pc|small=yes}}
{{Sex (biology) sidebar}}
'''Human reproduction''' is [[sexual reproduction]] that results in [[human fertilization]] to produce a human offspring. It typically<!-- NOTE: "Typically" is here because, as is clear from the rest of the lead and lower in the article, human reproduction can also be achieved via artificial insemination and assisted reproductive technology. Also, human cloning can theoretically be done, see [[animal cloning]].--> involves [[sexual intercourse]] between a [[sexual maturity|sexually mature]] human [[male]] and [[female]].<ref name=":1">{{Citation |last=Jones |first=Richard E. |title=The Male Reproductive System |date=1991 |work=Human Reproductive Biology |pages=72–93 |publisher=Elsevier |doi=10.1016/b978-0-12-389770-1.50008-1 |isbn=9780123897701 }}</ref> During sexual intercourse, the interaction between the [[male reproductive system|male]] and [[female reproductive system]]s results in fertilization of the [[ovum]] by the [[sperm]] to form a zygote.<ref name=":1" /> While normal cells contain 46 [[chromosome]]s (23 pairs), gamete cells only contain 23 single chromosomes, and it is when these two cells merge into one [[zygote]] cell that [[genetic recombination]] occurs and the new zygote contains 23 chromosomes from each parent, giving it 46 chromosomes (23 pairs).<ref name=":2">{{Cite web |title=Gametogenesis – an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/medicine-and-dentistry/gametogenesis |access-date=2022-09-12 |website=sciencedirect.com}}</ref> The zygote then undergoes a defined development process that is known as human embryogenesis, and this starts the typical 9-month [[gestation period]] that is followed by [[childbirth]]. The fertilization of the ovum may be achieved by [[artificial insemination]] methods, which do not involve sexual intercourse.<ref name=":3">{{Cite journal |last1=Ombelet |first1=W. |last2=Van Robays |first2=J. |date=2015 |title=Artificial insemination history: hurdles and milestones |journal=Facts, Views & Vision in ObGyn |volume=7 |issue=2 |pages=137–143 |issn=2032-0418 |pmc=4498171 |pmid=26175891 }}</ref> [[Assisted reproductive technology]] also exists.
Line 14 ⟶ 15:
===Male reproductive system ===
{{Further|Male reproductive system}}
The male reproductive system contains two main divisions: the [[testicle]]s where [[sperm]] are produced, and the [[human penis|penis]]
Male [[germ cell]]s produced in the testes are able to perform special [[DNA repair]] processes during meiosis that act to repair DNA damages and to maintain the integrity of the [[genome]]s that are to be passed on to progeny.<ref name = Garcia-Rodriguez2018>{{cite journal |vauthors=García-Rodríguez A, Gosálvez J, Agarwal A, Roy R, Johnston S |title=DNA Damage and Repair in Human Reproductive Cells |journal=Int J Mol Sci |volume=20 |issue=1 |date=December 2018 |page=31 |pmid=30577615 |doi=10.3390/ijms20010031 |doi-access=free |pmc=6337641 |url=}}</ref> Two of these DNA repair processes are [[homologous recombination]]al repair and [[non-homologous end joining]].<ref name = Garcia-Rodriguez2018/>
=== Female reproductive system ===
{{Further|Female reproductive system}}
The female reproductive system likewise contains two main divisions: the external genitalia (the [[Human vulva|vulva]]) and the internal genitalia.
The [[Egg cell|ovum]] meets with the [[sperm cell]]: a sperm may penetrate and merge with the egg, fertilizing it with the help of certain hydrolytic enzymes present in the acrosome. The fertilization usually occurs in the [[fallopian tube]]s, but can happen in the uterus itself. The [[zygote]] then becomes [[Implantation (human embryo)|implanted]] in the lining of the uterus, where it begins the processes of [[embryogenesis]] and [[morphogenesis]]. When the [[fetus]] is developed enough to survive outside of the [[uterus]], the cervix dilates and contractions of the uterus propel it through the birth canal, which is the [[Human vagina|vagina]], and thereby gives external life to the newborn [[infant]]. This process is called [[childbirth]].
The ova, which are the female sex cells, are much larger than the spermatozoon and are normally formed within the [[Ovary|ovaries]] of the female fetus before birth. They are mostly fixed in location within the ovary until their transit to the uterus, and contain nutrients for the later [[zygote]] and [[embryo]]. Over a regular interval known as the [[menstrual cycle]], in response to hormonal signals, a process of [[oogenesis]] matures one ovum which is released and sent down the fallopian tube. If not fertilized, this egg is flushed out of the system through [[menstruation]].
[[Oocyte]]s (female germ cells) located in the [[folliculogenesis|primordial follicle]] of the ovary are in a non-growing [[prophase]] arrested state, but are able to undergo highly efficient [[homologous recombination]]al repair of [[DNA damage (naturally occurring)|DNA damages]] including double-strand breaks.<ref name = Stringer2020>{{cite journal |vauthors=Stringer JM, Winship A, Zerafa N, Wakefield M, Hutt K |title=Oocytes can efficiently repair DNA double-strand breaks to restore genetic integrity and protect offspring health |journal=Proc Natl Acad Sci U S A |volume=117 |issue=21 |pages=11513–11522 |date=May 2020 |pmid=32381741 |pmc=7260990 |doi=10.1073/pnas.2001124117 |url=}}</ref> This capability allows the maintenance of [[genome]] integrity and protection of the health of offspring.<ref name = Stringer2020/>
== Process of fertilization ==
[[File:Biological life cycle of humans
[[Image:Da Vinci Coition of a Hemisected Man and Woman Luc Viatour.jpg|thumb|200px|right|"Coition of a Hemisected Man and Woman" ({{Circa|1492}}) by [[Leonardo da Vinci]]]]
Human reproduction normally begins with copulation, though it may be achieved through [[artificial insemination]], and is followed by nine months of pregnancy before childbirth. Pregnancy can be avoided with the use of contraceptives such as [[condom]]s and [[intrauterine device]]s.<ref>{{Cite journal |last1=Teal |first1=Stephanie |last2=Edelman |first2=Alison |date=2021-12-28 |title=Contraception Selection, Effectiveness, and Adverse Effects: A Review |url=https://jamanetwork.com/journals/jama/fullarticle/2787541 |journal=JAMA |language=en |volume=326 |issue=24 |pages=2507–2518 |doi=10.1001/jama.2021.21392 |pmid=34962522 |s2cid=245557522 |issn=0098-7484 |access-date=2022-09-12 |archive-date=2022-08-26 |archive-url=https://web.archive.org/web/20220826082329/https://jamanetwork.com/journals/jama/fullarticle/2787541 |url-status=live |doi-access=free }}</ref>
Line 31 ⟶ 36:
=== Copulation ===
{{Main|Sexual intercourse}}
Human reproduction naturally takes place as [[internal fertilization]] by sexual intercourse. During this process, the man inserts his erect [[Human penis|penis]] into the woman's [[Human vagina|vagina]] and then either partner initiates rhythmic [[pelvic thrust]]s until the man achieves [[orgasm]], which leads to [[ejaculation]] of [[semen]] containing sperm into the vaginal canal. The sperm and the ovum are known as the [[gametes]] (each containing half the genetic information of the parent, created through [[meiosis]]).<ref name=":2" /> The sperm (being one of approximately 250 million sperm in a typical ejaculation) travels through the vagina and cervix into the uterus or fallopian tubes. Only 1 in 14 million of the ejaculated sperm will reach the fallopian tube. The egg simultaneously moves through the fallopian tube away from the ovary. One of the sperm encounters, penetrates and fertilizes the ovum, creating a [[zygote]]. Upon [[Human fertilization|fertilization]] and [[Implantation (human embryo)|implantation]], gestation of the fetus then occurs within the uterus.<ref>{{cite journal |author=Ghazal, S, Kulp Makarov, J |url=http://www.glowm.com/section_view/heading/Egg%20Transport%20and%20Fertilization/item/316 |title=Egg Transport and Fertilization |journal=The Global Library of Women's Medicine |year=2014 |issn=1756-2228 |doi=10.3843/GLOWM.10317 |access-date=May 8, 2016 |display-authors=etal |archive-date=May 13, 2016 |archive-url=https://web.archive.org/web/20160513065553/http://www.glowm.com/section_view/heading/Egg%20Transport%20and%20Fertilization/item/316 |url-status=live }}</ref><ref>{{cite web |url=https://www.ucsfhealth.org/education/conception_how_it_works/ |title=Conception: How It Works |publisher=The Regents of The University of California |year=2002 |access-date=May 8, 2016 |archive-date=March 15, 2016 |archive-url=https://web.archive.org/web/20160315083424/https://www.ucsfhealth.org/education/conception_how_it_works/ |url-status=live }}</ref><ref>{{cite web |url=http://www.completefertility.co.uk/fertility_basics.php |title=Fertility Basics |work=Complete Fertility Centre Southampton |publisher=Complete Fertility Ltd |year=2015 |access-date=May 8, 2016 |archive-date=May 8, 2016 |archive-url=https://web.archive.org/web/20160508060750/http://www.completefertility.co.uk/fertility_basics.php |url-status=live }}</ref><ref>{{cite web |url=http://www.webmd.com/baby/guide/understanding-conception |title=Conception & Pregnancy: Ovulation, Fertilization, and More |publisher=WebMD, LLC |year=2016 |access-date=May 8, 2016 |archive-date=May 8, 2016 |archive-url=https://web.archive.org/web/20160508202313/http://www.webmd.com/baby/guide/understanding-conception |url-status=live }}</ref>
[[File:Pregnancy chance by day near ovulation.jpg|thumb|Chance of [[human fertilization|fertilization]] by [[menstrual cycle]] day relative to ovulation<ref name="DunsonBaird1999">{{cite journal|last1=Dunson|first1=D.B.|last2=Baird|first2=D.D.|last3=Wilcox|first3=A.J.|last4=Weinberg|first4=C.R.|author4-link=Clarice Weinberg|title=Day-specific probabilities of clinical pregnancy based on two studies with imperfect measures of ovulation|journal=Human Reproduction|volume=14|issue=7|year=1999|pages=1835–1839|issn=1460-2350|doi=10.1093/humrep/14.7.1835|doi-access=free|pmid=10402400}}</ref>]]
[[Pregnancy rate#Pregnancy rate for sexual intercourse|Pregnancy rates for sexual intercourse]] are highest during the [[menstrual cycle]] time from some 5 days before until 1 to 2 days after ovulation.<ref>Pages.242,374 in: {{cite book|title=Taking Charge of Your Fertility|url=https://archive.org/details/takingchargeofyo00toni|url-access=registration|last=Weschler|first=Toni|publisher=HarperCollins|year=2002|isbn=0-06-093764-5|edition=Revised|location=New York|pages=[https://archive.org/details/takingchargeofyo00toni/page/359 359–361]}}</ref> For optimal pregnancy chance, there are recommendations of sexual intercourse every 1 or 2 days,<ref>{{cite web|url=https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/how-to-get-pregnant/art-20047611|title=How to get pregnant|website=[[Mayo Clinic]]|date=2016-11-02|access-date=2018-02-16|archive-date=2020-05-18|archive-url=https://web.archive.org/web/20200518223708/https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/how-to-get-pregnant/art-20047611|url-status=live}}</ref> or every 2 or 3 days.<ref>{{cite web|url=https://www.nice.org.uk/guidance/cg156/ifp/chapter/trying-for-a-baby|title=Fertility problems: assessment and treatment, Clinical guideline [CG156]|website=[[National Institute for Health and Care Excellence]]|access-date=2018-02-16|archive-date=2018-02-17|archive-url=https://web.archive.org/web/20180217082533/https://www.nice.org.uk/guidance/cg156/ifp/chapter/trying-for-a-baby|url-status=live}} Published date: February 2013. Last updated: September 2017</ref> Studies have shown no significant difference between different [[sex positions]] and pregnancy rate, as long as it results in [[ejaculation]] into the
===Alternative methods===
| |||