Human Reproduction. Human Reproductive System MaleFemale.

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.