Human Reproduction

Human Reproduction

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

Male or Female???DNA determines baby’s genderXX = Female Chromosome XY = Male ChromosomeDepends on which egg & sperm get together.Father determines baby’s gender by contributing an X or Y. Mother can only contribute an X.

Anatomy – similaritiesFunction – VERY different!

MaleUncomplicatedProduce 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!

Ovulation- One egg released from ovary to fallopian tube Hyperovulation- more than one egg released from ovary to fallopian tube

After OvulationEgg pushed along by ciliaCan be fertilized in the fallopian tube and is viable for 12-24 hoursFew days travel time to arrive in uterus

Menstrual CycleComplex combination of 10-12 chemicals (hormones)Usually one egg once a monthAll about timing!!! Sperm can live up to 5 days in the female’s body. An ovum is only viable for 12 to 24 hours. A woman can get pregnant anytime from about five days prior to ovulation to even occasionally two days after, for a total of about seven days.

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 Stages1. 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 pregnant- while egg is traveling in the fallopian tube.

Egg gets fertilized while traveling through oviduct.Technically, ovulation takes place two weeks before the onset of the next period.

Cycles can differ and women’s cycle length differs

If fertilized…Zygote begins to divide as it travels through fallopian tubeImplants into lining of uterus

If not fertilized…Egg travels through the fallopian tube to uterusExits body with blood and tissues during 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

Vasectomy (medical procedure)Cut/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 3-5 days(hostile environment)

Sperm….Several Parts:

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

MitochondriaEnergy

TailSwimming / propulsion

Prostate GlandAdds non-sperm stuff to semen

pH buffersNourishment

Prostate CancerSlower-growing (usually)Surgery for removal

Conception/FertilizationEjaculation

Release of 300-500 million sperm

Egg needs to be in the fallopian tubeSperm to egg, not an easy task

Go wrong direction : 2 paths – only 1 leads to an eggGet attacked by female’s white blood cellsAcidic environmentTiming

Once egg is located…

Dissolve protective coating surrounding the eggOne gets through – enters eggInstant biochemical change in zygote

No more sperm allowed in

Zygote begins development

The united egg and sperm is called zygote.

Within 36 hours, while the zygote is still traveling through the fallopian tube, it

begins to divide.

The BlastocystFrom the two-cell stage until about nine weeks after fertilization, the growing structure is called embryo. About 5 days after fertilization, the embryo reaches the uterus. By this time it is made up of about 500 cells.

Implants in uterine lining

Endometrium= outer lining of uterusBecomes placenta

Uses mother’s nutrientsContinues development

Healthy PregnancyPrenatal Care: monitoring toolsProper nutritionPrenatal vitaminsExerciseAvoiding alcohol and drugsAvoiding environmental hazards (x-rays, lead, mercury, cat litter)

Fetal DevelopmentAmniotic Sac: Soon after implantation, a fluid filled bag of thin tissue develops around the embryo. The sac continues to grow in size as the embryo grows.Inside the sac is amniotic fluid. “water breaking”

Placenta

• Lines part of the wall of the uterus during pregnancy and nourishes the embryo with substances from the mother’s blood. (oxygen, nutrients, etc)

• Dangerous substances can pass between mother to baby too. (alcohol, drugs, chemicals)

Umbilical Cord– About 25 days after fertilization, a

cordlike structure develops between the embryo and the placenta.

– Blood vessels from placenta to baby– Mom’s & baby’s blood do not circulate

together!• Can have 2 different blood types• Diffusion

Growing Fetus• From the 3rd month until birth the baby

is called a fetus.• During the 3rd to 6th month, the fetus begins to move

and kick. (nervous system matures, sense organs develop, and the fetus becomes sensitive to light and sound, fetus alternates periods of activity and sleep)

• During the seventh to ninth month, the fetus continues to grow and develop. The size of the body increases and body fat accumulates.

• By 40 weeks, the fetus is ready to be BORN!

Stages of Birth• Labor• Contractions begin• Cervix begins to dilate and efface• Contractions every five minutes

and lasting 40 to 60 seconds • Early labor ends around 4 cm

dilated

Stages of Birth• Transition & Delivery• Cervix dilates from 8 to a full 10

centimeters • This is the most intense part of labor. • Contractions are strong, coming

every two and a half to three minutes or so and lasting a minute or more

• Time to “push”

Stages of Birth • Delivering the afterbirth• Minutes after giving birth, your

uterus begins to contract again.• The first few contractions usually

separate the placenta from your uterine wall.

• Nurses gently push to help expel the placenta

Breastfeeding• Most nutritious option for baby

– Milk changes as baby grows

• Antibodies from mom create immunity for baby• Can protect baby from allergies• Can protect mother from postpartum depression• Breastfeeding may reduce risk of breast cancer• Studies have shown correlation between

breastfeeding and higher intelligence in baby• Bond w/baby is stronger• Helps Mom lose weight & uterus to shrink back

Full term• Babies are considered full term at 37 weeks• Pregnancy is typically 40 weeks (280 DAYS)

• Pregnancy is broken into trimesters– 1st – 1-3 months– 2nd- 3-6 months– 3rd-6-9 months

• Doctor’s appointments– Start monthly– Around 28 weeks- every 2 weeks– @35 weeks- weekly