This document provides an overview of human reproduction, including the similarities and differences between male and female anatomy and the processes of conception, pregnancy, and birth. It explains that early in development, a fetus starts with parts that could develop into either gender, but DNA determines whether it becomes male or female. For females, it describes the menstrual cycle and role of hormones, as well as how one egg is released each month. For males, it outlines sperm production and the role of testes, vas deferens, and other structures. The document then explains fertilization, fetal development, and the different types of twins.

1. Human Reproduction

2. Battle of the sexes!!!
Are males and
females all that
different?
Well…..
Yes
And
No!

3. Anatomy
Male Female

4. Similarities
2 pouches
Testicles
Ovaries
Start out inside body
Testicles “descend” before birth
Fetus begins with “starter parts” that
could develop into either gender.

5. 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)

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

7. Anatomy – similarities
Function – VERY different!
Male
Uncomplicated
Produce sperm
2-4 MILLION
every day
Female
Very Complicated!
One egg
Once a month
Careful coordination
of hormones & body
Timing perfect!

8. Females
Ovaries
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)

10. 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

11. 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

12. 28-Day Cycle (average)
Three Stages
1. Tear Down
2. Rebuild
3. Extra nutrients/blood for potential baby
No Baby?
Back to #1

13. Chemicals (hormones)
Regulate events in the body
Estrogen
Progesterone
LH (leuteinizing hormone)
FSH (follicle stimulating hormone)
Many others

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

15. ~Day 14
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

17. If fertilized…
Zygote begins to divide as it travels
through oviduct
Implants into lining of uterus

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

19. Birth Control Pills
“Trick” body into thinking it’s pregnant
Extra hormones
No ovulation occurs
No ovulation = no egg = no fertilization = no baby!
No hormones taken for 7 days = menstruation

20. Male
Testes
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
Vasectomy
Cut/tie off tube – sperm can’t get out!

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

22. What is sperm?
Then…
Used to think it was a tiny human
inside each cell
Spermists vs. Ovists

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

24. Prostate Gland
Adds non-sperm stuff to semen
pH buffers
Nourishment
Cancer very common
Slower-growing (usually)
Surgery for removal

25. Bulbourethral gland
Adds lubricant to aid travel of semen
through the urethra

26. Conception/Fertilization

27. 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

28. Once egg is located…
Dissolve protective goo surrounding
egg
One gets through – enters egg
Instant biochemical change in zygote
No more sperm allowed in

29. Zygote begins development
Time Lapse
Development

30. Implants in uterine lining
Endometrium= outer lining of uterus
Becomes placenta
Uses mother’s nutrients
Continues development

31. Fetal Development
Anmion
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

33. 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

35. Ancient beliefs
Wak Wak tree

36. 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

37. 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

38. Twins/Multiple Births
Two types
Monozygotic
From one egg
Identical
Dizygotic
From two eggs
Fraternal
Not identical

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

40. 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

41. 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.