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Sexual Reproduction in Humans. By Vittoria Rizzardi. It all start like this …. External reproductive structures.

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sexual reproduction in humans

SexualReproduction in Humans

By Vittoria Rizzardi

external reproductive structures
  • Penis— Ithasthreeparts; the root, whichattaches to the wall of the abdomen. the body(or shaft) and the glans. The glans, whichalsoiscalled the head of the penis, iscovered with a layer of skincalledforeskin. The penisalsocontains a number of sensitive nerveendings.Thebody of the penisconsists of threeinternalchambers. Thesechambers are made up of erectiletissue. Thistissuecontainsthousands of large spacesthatfill with bloodwhen the man issexuallyexcited. This help the penis to becomerigid and erect, whichallows for penetrationduringsexualintercourse. Whenthe penisiserect, the flow of urine isblocked from the urethra, allowingonlysemen to be ejaculatedatorgasm.
  • Scrotum— The scrotumisthe sac of skinthathangsbehind the penis. Itcontains the testicles, aswellasmanynerves and bloodvessels. The scrotumhas a protectivefunction and actsas a climate control system for the testes. For normalspermdevelopment, the testes must be at a temperature slightly cooler than the body temperature. Special muscles in the wall of the scrotumallowit to contract and relax, moving the testiclescloser to the body for warmingitor fartheraway from the body to cool the temperature.
  • Testicles (testes) — The testes are ovalorgansthatlie in the scrotum, protectedateither end by a structurecalled the spermaticcord. The testes are responsible for making testosterone, the primary male sex hormone, and for generatingsperm. Within the testesare tubescalledseminiferoustubules. Thesetubules are responsible for producing the spermcellsthrough a processcalledspermatogenesis.
internal reproductive organs
  • Urethra — The urethrais the tube thatcarries urine from the bladder to outside of the body. In males, ithas the additionalfunction of expellingsemenwhen the man reachesorgasm. When the penisiserectduring sex, the flow of urine isblocked from the urethra, allowingonlysemen to be ejaculatedatorgasm.
  • Prostate gland — The prostate glandithas a circularstructurethatislocatedbelow the urinarybladder in front of the rectum. The prostate glandcontributesby addingfluid to the ejaculate. Prostate fluidsalso help to feedthe sperm. The urethra, whichcarries the ejaculate to be expelledduringorgasm, runsthrough the center of the prostate gland.
  • Spermducts — These are formed by the fusion of the vasdeferens and the seminalvesicles. The spermductsemptyinto the urethra.
differences between female and male gametes
Differencesbetweenfemale and male gametes
  • 1 The female gamete , the egg, isalotlotbiggerthan the sperm.

Female gamete egg:

Male gamete egg:


2The testes produce millions of sperm, whereasthe ovariesrelease 1 egg per month.

  • 3The spermmoveall the way through the cervix and into the falopina tube , whereas the eggdoesntmove by itselfbutismoved by tinyhaircalledfollicles.
menstrual cycle in terms of changes in the ovaries
Menstrualcycle in terms of changes in the ovaries
  • The ovaries produce estrogen and progesterone, hormonesthat cause the eggs in the ovaries to mature so the woman can becomepregnant. Everymonth, oneeggleavesone of the ovaries on its way to the uterus via the fallopiantubes.
in terms of the uterus terms of the uterus
  • In preparation for the egg, the uterusstarts to develop a thickerlining and it’swallsbecomecushiony (thisiscalled the endometriallining). If the eggreaches the uterus and isfertilized by a spermcell due to sexualintercourse, itattaches to the endometriallining and the woman becomespregnant.
development of the zygote
Development of the zygote
  • The zygote first dividesintotwoidenticalcells, calledblastomeres. They continue to subdivide once every 12 to 20 hours as the zygoteslowlypasses down the fallopiantubes. Itdevelopsinto a morulla and blastocyst.
  • Therefore the start of the pregnancyisabout 10 daysafterconception, when the blastocystimplantsitself in the innerwall of the uterus.
functions of the amniotic sac and fluid
Functions of the amnioticsac and fluid
  • Amnioticfluidis a pale yellowfluidthatisusedas a cushion the unborn baby from moving. Itprovides a stable temperature and assists in maintaining a consistent body temperature for the baby.
The fluidallows the baby to movefreely and exercisegrowingmuscles to develop a symmetricalmusculoskeletalsystem.
  • The amnioticsacbegins to fill with fluidshortlyafterconception; sometime in the first two weeks of pregnancy. The amount of fluidincreasesas the baby grows and thendecreasesatabout 38 weeks gestation. After the 9 months the sacruptures and the fluidisdrainedthrough the vagina.
functions of the placenta
Functions of the placenta
  • The placenta’sprimaryroleis to ensurethatoxygenismovedintothe baby’sbloodstream and carbon dioxideiscarriedawayfrom the baby, however the wasteisnotlimited to oxygenbutalsoincludescleaning out otherwastewhichisproduced by the baby. In the same way thatitensuresoxygenreachesthe fetus, italsotake care in ensuringthat some nutrients are received.
functions of the umbilical cord
Functions of the umbilicalcord
  • The umbilicalcordis the lifelinebetween the fetus and placenta. Itisformed by the 5th week of development and itfunctionsthroughoutpregnancyisto protect the vesselsthattravelbetween the fetus and the placenta.
advantages of breast feeding
Advantages of breast-feeding
  • Healthiestoption for the baby
  • More convenient, don'thave to get up in the middle of the night to mix/heat formula
  • Lessexpensive, infactitis free
  • Helpslosepregnancyweight,burns up to 500 calories per day
  • Lessens post-partumbleeding
  • Releaseshormonesthat are relaxing
  • Can be usedas a birth control method (carefully)
  • Lowersrisk for cancer
transmission of hiv
Transmission of HIV
  • HIV can be transmitted in 3 ways:
  • Throughcontaminatedblood, unsterile or dirtyinstrumentsused for circumcision.
  • Throughsexualacts, for example no usingprecautionslikecondoms.
  • Mother to child, isone of the major causes of HIV infection in children.
hiv aids prevenctions
HIV/AIDS prevenctions
  • Abstinence(notengaging in sex, or delaying first sex)
  • Beingsafer, by beingfaithful to one's partner or reducing the number of sexualpartners
  • Correctand consistent use of condoms.
some questions
Some questions…




Explain the functions of the internalreproductiveorgans.

Which are the differencesbetween the female and male gametes?

Explain the menstrualcycle in terms of changes in the ovaries.