Human Reproduction
Mar 31, 2015
Human Reproduction
Human Reproductive System
Male Female
Male or Female???DNA determines baby’s genderXX = FemaleXY = MaleDepends on which egg & sperm get together.Father determines baby’s gender.
MaleUncomplicatedProduce sperm
2-4 MILLION every day
FemaleVery Complicated!One eggOnce a monthCareful coordination of hormones & bodyTiming perfect!
FemalesOvaries
2 pouchesContain ova
Born with all of her eggs (~ 400,000)Use up ~500Won’t run out!
OvulationOne egg released from ovary to oviduct (fallopian tube)
After OvulationEgg pushed along by ciliaFew days travel time to arrive in uterus
Cervix – Opening between uterus & vagina
Normally tinyAt birth – muscles pull open (dilation) cervix to allow baby to pass through = Labor
Menstrual CycleComplex combination of 10-12 chemicals (hormones)Usually one egg once a monthAll about timing!!!
Uterus must be ready when egg gets there in case it was fertilizedIf no fertilization, tear down lining of uterus and rebuild for next month
28-Day Cycle (average)Three Stages
1. Tear Down2. Rebuild3. Extra nutrients/blood for potential
baby
No Baby?Back to #1
Chemicals (hormones)Regulate events in the body
EstrogenProgesteroneMany others
Day 1First menstrual blood & tissueNo baby = breaks down lining of uterus5-7 days of blood/tissue exits body
Pre-Ovulation
~Day 14Ovulation = Egg releasedTemp spikes slightlyMost fertile in next few days!
Able to get pregnant
Egg gets fertilized while traveling through oviduct.
Post-Ovulation
If fertilized…Zygote begins to divide as it travels through oviductImplants into lining of uterus
If not fertilized…Egg travels through oviduct to uterusExits body with blood and tissues during menstruation
Birth Control Pills“Trick” body into thinking it’s pregnant
Extra hormonesNo ovulation occursNo ovulation = no egg = no fertilization = no baby!
MaleTestes
Produce 2-4 million sperm every day Outside body – why?
Sperm like temps 1-2 cooler than body temp
Vas DeferensTube sperm travel through
SemenContains
300-500 million spermSperm foodpH buffers
Allows sperm to survive for a couple of days inside female’s body
Now…Contains Several Parts:
HeadChemical to dissolve egg gooDad’s genetic information (DNA)
MitochondriaEnergy
TailSwimming
Prostate GlandAdds stuff to semen
pH buffersNourishment
Conception/Fertilization
Conception/FertilizationEjaculation
Release of 300-500 million sperm
Egg needs to be in oviductSperm to egg, not an easy task
Go wrong direction : 2 paths – only 1 leads to an eggGet attacked by female’s white blood cellsAcidic environmentCurrent
Once egg is located…Dissolve protective goo surrounding eggOne gets through – enters eggInstant biochemical change in zygote
No more sperm allowed in
Gamete – Sex cell; sperm and ova
Zygote – Cell formed after male and female gametes join immediately following fertilization
Zygote begins development
Implants in uterine liningBlastocyst implants in outer lining of uterusUses mother’s nutrientsContinues development
Fetal DevelopmentAnmion
Membrane surrounding babyContains amniotic fluidBreaks just before birth = “water broke”
Amniotic FluidThe “water” – surrounding babyBuoyant cradle for baby
ProtectionFree movement
Fetal Dev (cont’d)Umbilical Cord
Blood vessels from placenta to babyMom’s & baby’s blood do not circulate together!
Can have 2 different blood typesDiffusion
BirthLabor – muscles used to open cervixBaby flips upside down– Head first!– Feet first = Breech (bad)
• Cesarian Section (“C-section”) surgical removal of baby
• After baby is born mom delivers placenta (“afterbirth”) that detaches from uterus
Breastfeeding• Most nutritious option for baby
– Milk changes as baby grows• Antibodies from mom create
immunity for baby• Studies have shown correlation
between breastfeeding and higher intelligence in baby.
• Bond w/baby is stronger
Twins/Multiple Births• Two types
– Monozygotic• From one egg• Identical
– Dizygotic• From two eggs• Fraternal• Not identical
Identical twins• One zygote• Splits in 2• No one knows why!• Completely random =
does NOT run in families
• Same exact DNA• Nature’s clones
Fraternal Twins• 2 separate eggs get
fertilized with 2 different sperm cells
• More than one egg got released during ovulation
• Siblings– Can be sisters– Brothers– Brother and sister
• Tends to run in families
Conjoined Twins• Used to be called “Siamese” twins• First well known case was in Siam• Identical twins that never
completely separated during development
• Sometimes can be separated, depending on what is shared.