2.  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

3.  Three Stages 1. Tear Down 2. Rebuild 3. Extra nutrients/blood for potential baby  No Baby? › Back to #1

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

5.  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

6.  Egg travels through oviduct to uterus  Exits body with blood and tissues during menstruation

7.  Ejaculation › Release of 300-500 million sperm are deposited just a few inchesaway from the fallopian tubes..  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. › Sperms can be inside 72 hours. › The genetic information is inside the head of sperm.

8.  Dissolve protective goo surrounding egg  One gets through – enters egg  Instant biochemical change in zygote › No more sperm allowed in because of a protective shield.

9. When it´s fertilized, it continuous to travel through the fallopian tube to ward uterus. After 30 hours the fertilized eggs divides into two cells and is called an Embryo.

10.  Endometrium= outer lining of uterus › Becomes placenta  Uses mother’s nutrients  Continues development

11.  Umbilical Cord › Blood vessels from placenta to baby › Mom’s & baby’s blood do not circulate together!  Can have 2 different blood types  Diffusion

12.  The embryo grows rapidly: A heart and brain begins to form, eyes appear, the face take shapes, small buds become into legs and arms. Also internal organs: lungs, stomach and liver.

13.  Baby’s body is “told” by DNA to become either male or female.  “Unused” parts disintegrate  “Used” parts continue development  (see overhead)

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

15. STAGEMAJOR CHANGES 0-4 WEEKS Fertilization occurs, embryo travels through fallopian tubes and implants in uterine wall, brain, ears and arms begin to form, heart forms and begins to beat. 5-8 WEEKS Nostrils, eyelids, nose, hands, fingers, legs, feet, toes and bones begin to form, females develop ovaries, male develop testes. Cardiovascular system is working. About 22mm 9-12 WEEKS Embryo becomes a fetus, penis of males is distinct, growth of chin and other facial structures give fetus a human face and profile. 36mm 13-16 WEEKS Blinking of eyes, sucking of lips occurs, body begins to outgrow head, mother can feel muscular activity of fetus. 140mm 17-20 WEEKS Limbs achieve final proportions, eyelashes and eyebrows are present; about 190 mm. 21-30 WEEKS Substantial increase in weight, may survive if born at this stage; skin is wrinkled and red, about 280mm 30-40 WEEKS Fingernails and toenails are present; about 360mm

18.  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

19.  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

20.  Two types › Monozygotic  From one egg  Identical › Dizygotic  From two eggs  Fraternal  Not identical

21.  One zygote  Splits in 2  No one knows why!  Completely random = does NOT run in families  Same exact DNA  Nature’s clones

22.  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

23.  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.