Human Reproduction

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

Anatomy MaleFemale

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

Around 7 th 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 gender XX = Female XY = Male Depends on which egg & sperm get together. Father determines baby’s gender.

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!

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)oviduct

After Ovulation Egg pushed along by cilia Few days travel time to arrive in uterusuterus CervixCervix – 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 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 1. Tear Down 2. Rebuild 3. Extra nutrients/blood for potential baby No Baby? Back to #1

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

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

~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

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! No hormones taken for 7 days = menstruation

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!

Testosterone LH GnRH FSH

Semen Contains million sperm Sperm food pH 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 cell Spermists vs. Ovists

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

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

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

Conception/Fertilization

When Egg Meets Sperm…

Conception/Fertilization Ejaculation Release of 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

Zygote begins developmentdevelopment Time Lapse Development

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

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

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

The Placenta

The Amniotic Sac

5 Weeks Embryo is about 5 mm long (about the size of a pea) Eyes and mouth beginning to form

6 Weeks Embryo is about 9 mm in length (About the size of a bean) Facial features, such as the upper nose and lip are forming. Eye and ear are more clearly defined.

7 Weeks Embryo is about the size of a penny (16 mm) Head is enlarging Facial structures such as eyelids are forming. Genetic decision as to gender occurs.

8 Weeks Embryo is about the size of a nickel (18 mm) Sexual differentiation occurs. Limbs are becoming more developed, and are bent at the elbow. Fingers are present, but are webbed.

9-10 Weeks Fetal period begins. Fetus is roughly the size of a peanut in it’s shell (30 mm.) Physical structures are easily identifiable (i.e. wrist, elbow, knee, toes etc.) External genitalia begin to develop.

Weeks Fetus is mouse-sized (~60 mm.) Fetus can make a fist with its finger. Arms, hands, fingers, legs, feet, and toes are fully formed Testosterone is produced by the testes in male fetus.

Weeks Fetus grows from 7.4 to 11.6 cm during this time. The brain is fully developed and the fetus can swallow. Fetus makes active movements including kicks and even somersaults. Muscles tissue is lengthening and bones are becoming harder.

20 Weeks Fetus is about 26 cm long from head to toe. Finger and toenails appear. Sex organs are visible on ultrasound devices. Mother can feel the fetus moving Lanugo, a fine hair now covers the entire body.

24 Weeks Fetus has grown to 30 cm in length. Fetus has a hand and startle reflex. Footprints and fingerprints are forming. Fetus practices breathing by inhaling amniotic fluid into its developing lungs.

Weeks Fetus grows to 37 cm by week 28. Rapid brain development occurs. The nervous system is able to control some bodily functions. Fetus’ eyelids open and close. At 25 weeks there is a 60% chance of survival if born. The fetus is considered legally viable at 28 weeks and there is a 90% chance of survival if born at this point.

Weeks Fetus will grow to 42 cm by the end of week 32. There is a rapid increase in the amount of body fat the fetus has. Rhythmic breathing occurs, but the lungs are not yet mature. The fetus sleeps 90-95% of the day. At this point there the survival rate is above 95% if the baby is born.

Week 32 to Birth Fetus will grow to around 50 cm, and around 7.5 pounds at the time of birth. Hair on the baby’s head is now coarser and thicker. The lungs are mature. At birth the placenta detaches from the uterus and the umbilical cord will be cut as the baby takes his first breaths of air. Breathing will trigger changes in the heart and bypass arteries forcing all blood to now travel through the lungs.

Ancient beliefs Wak Wak tree

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.