Human Reproduction

Battle of the sexes!!!Are males and females all that different?Well…..

YesAndNo!

Anatomy

Male Female

Similarities2 pouches

TesticlesOvaries

Start out inside bodyTesticles “descend” before birth

Fetus begins with “starter parts” that could develop into either gender.

Around 7th Week…Baby’s body is “told” by DNA to become either male or female.“Unused” parts disintegrate“Used” parts continue development(see overhead)

Male or Female???DNA determines baby’s genderXX = FemaleXY = MaleDepends on which egg & sperm get together.Father determines baby’s gender.

Anatomy – similaritiesFunction – VERY different!Male

UncomplicatedProduce 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 & vaginaNormally 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

EstrogenProgesteroneLH (leuteinizing hormone)FSH (follicle stimulating hormone)Many 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 pregnantEgg 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!No hormones taken for 7 days = menstruation

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

VasectomyCut/tie off tube – sperm can’t get out!

SemenContains

300-500 million spermSperm foodpH buffers

Allows sperm to survive for a couple of days inside female’s body (hostile environment)

What is sperm?Then…

Used to think it was a tiny human inside each cellSpermists vs. Ovists

Now…Contains Several Parts:

HeadChemical to dissolve egg gooDad’s genetic information (DNA)

MitochondriaEnergy

TailSwimming

Prostate GlandAdds non-sperm stuff to semen

pH buffersNourishment

Cancer very commonSlower-growing (usually)Surgery for removal

Bulbourethral glandAdds lubricant to aid travel of semen through the urethra

Conception/Fertilization

Conception/FertilizationEjaculation

Release of 300-500 million spermEgg 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

Zygote begins development

Time Lapse Development

Implants in uterine liningEndometrium= outer lining of uterus

Becomes placentaUses 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

Ancient beliefsWak Wak tree

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

BreastfeedingMost nutritious option for baby

Milk changes as baby growsAntibodies from mom create immunity for babyStudies have shown correlation between breastfeeding and higher intelligence in baby.Bond w/baby is stronger

Twins/Multiple BirthsTwo types

MonozygoticFrom one eggIdentical

DizygoticFrom two eggsFraternalNot identical

Identical twinsOne zygoteSplits in 2No one knows why!Completely random = does NOT run in familiesSame exact DNANature’s clones

Fraternal Twins2 separate eggs get fertilized with 2 different sperm cellsMore than one egg got released during ovulationSiblings

Can be sistersBrothersBrother and sister

Tends to run in families

Conjoined TwinsUsed to be called “Siamese” twinsFirst well known case was in SiamIdentical twins that never completely separated during developmentSometimes can be separated, depending on what is shared.