Human Reproduction

Human Reproductive System Male Female

Male or Female??? DNA determines baby’s gender XX = Female XY = Male Depends on which egg & sperm get together. Father determines baby’s gender.

Male Female Uncomplicated Produce sperm 2-4 MILLION every day Very Complicated! One egg Once a month Careful coordination of hormones & body Timing perfect!

Females Ovaries Ovulation 2 pouches Contain ova Born with all of her eggs (~ 400,000) Use up ~500 Won’t run out! Ovulation One egg released from ovary to oviduct (fallopian tube)

After Ovulation Egg pushed along by cilia Few days travel time to arrive in uterus Cervix – Opening between uterus & vagina Normally tiny At birth – muscles pull open (dilation) cervix to allow baby to pass through = Labor

Menstrual Cycle Complex combination of 10-12 chemicals (hormones) Usually one egg once a month All about timing!!! Uterus must be ready when egg gets there in case it was fertilized If no fertilization, tear down lining of uterus and rebuild for next month

28-Day Cycle (average) Three Stages No Baby? Tear Down Rebuild Extra nutrients/blood for potential baby No Baby? Back to #1

Chemicals (hormones) Regulate events in the body Estrogen Progesterone Many others

Day 1 Pre-Ovulation First menstrual blood & tissue No baby = breaks down lining of uterus 5-7 days of blood/tissue exits body Pre-Ovulation

~Day 14 Post-Ovulation Ovulation = Egg released Temp spikes slightly Most 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 oviduct Implants into lining of uterus

If not fertilized… Egg travels through oviduct to uterus Exits body with blood and tissues during menstruation

Birth Control Pills “Trick” body into thinking it’s pregnant Extra hormones No ovulation occurs No ovulation = no egg = no fertilization = no baby!

Male Testes Vas Deferens Produce 2-4 million sperm every day Outside body – why? Sperm like temps 1-2 cooler than body temp Vas Deferens Tube sperm travel through

Semen Contains 300-500 million sperm Sperm food pH buffers Allows sperm to survive for a couple of days inside female’s body

Now… Contains Several Parts: Head Mitochondria Tail Chemical to dissolve egg goo Dad’s genetic information (DNA) Mitochondria Energy Tail Swimming

Prostate Gland Adds stuff to semen pH buffers Nourishment

Conception/Fertilization

Conception/Fertilization Ejaculation Release of 300-500 million sperm Egg needs to be in oviduct Sperm to egg, not an easy task Go wrong direction : 2 paths – only 1 leads to an egg Get attacked by female’s white blood cells Acidic environment Current

Once egg is located… Dissolve protective goo surrounding egg One gets through – enters egg Instant 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 lining Blastocyst implants in outer lining of uterus Uses mother’s nutrients Continues development

Fetal Development Anmion Amniotic Fluid Membrane surrounding baby Contains amniotic fluid Breaks just before birth = “water broke” Amniotic Fluid The “water” – surrounding baby Buoyant cradle for baby Protection Free movement

Fetal Dev (cont’d) Umbilical Cord Blood vessels from placenta to baby Mom’s & baby’s blood do not circulate together! Can have 2 different blood types Diffusion

Birth Labor – muscles used to open cervix Baby 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.