Reproduction & Development

Fertilization: Sperm• 200-500million haploid sperm

cells swim to uterine tube• 30 min-2hrs only 10,000 sperm

reach the uterine tube• Live for up to 48 hours waiting

for oocyte (egg)…only 100 reach the oocyte

• Acrosome cap w/enzymes• Flagellum falls off once enters

egg

Fertilization: Oocyte

• Oocyte 2000x larger than sperm

• Found in upper 1/3 of uterine tube w/in one day if ovulation

• Several sperm required to penetrate corona radiata

• Only one sperm can penetrate the zona pellucida

• Then enzymes prevent other sperm from entering

• This activates oocyte to complete meiosis

Gestation: Prenatal Development

• Cleavage – (day 1-6) – mitotic cell divisions as

travels down uterine tube– w/in 30hrs zygote divides

to form blastomeres– Blastomeres divide every

10-12 hrs– Day 3 – morula – solid

ball of cells– Day 5-6 blastocyst –

hollow ball of cells, cells begin to differentiate

Gestation: Implantation

• Implantation• Day 7-10: blastocyst

adheres to uterine lining• Days 10-12:

differentiation continues to form Amniotic cavity, Yolk sac (blood cell formation), and germ layers

• Germ layers: – Endoderm– Mesoderm– Ectoderm

Gestation: Placentation• Placenta – allows diffusion between fetal and maternal circulation

(blood barrier)• By week 3 – Placenta begins to form

– Produces hCG – prevents mensus

• By week 4 – yolk sac shrinks and fuses into umbilical cord• By week 10-12 – placenta produces estrogens and progesterone,

ovaries become non functional

First TrimesterEmbryonic development

• 3-4 weeks– Neural tube begins

• 5 weeks– 2mm– “c” shaped– Heart bulge– Functional yolk sac & placenta

• 6-7 weeks– .5” (tadpole w/gills slits)– Heart beats– Neural tube closes– Arm & leg buds– Lungs, nostrils, lenses, and dig tract forms

• 8-10 weeks– 1”– Muscles – 1st movements– Ovaries/testes form– Fingers/toes, ears/lips develop– Bones ossify

• 11-13 weeks (Fetus)– 2-3”– Nails, vocal chords, kidneys (urine), and ears– Reflexes, hiccups (diaphragm), rollover, stretch– Pancreas, gall bladder, wbc

Maternal Development• Fatigue• Morning sickness• Tender breasts• Decreased bp, lightheaded & dizzy• Blood volume increases• Require 10-30% more nutrients and

vitamins• Frequent urination

Second TrimesterFetal Development

• 14-18 wks– 4-6” (lobster tail)– Fingerprints, auditory ossicles, teeth, hair &

eyebrows– Make faces, eyes move & detect light– Suck thumb

• 19-22 wks– 8-10” (small grapefruit)– Taste buds, – sense touch, and stress– Perm teeth– Myelination of ns– L/R handed– Ovaries produce eggs

• 23-27 wks– 11-15”, 2lbs (bag coffee)– Recognize voices and respond– Fat deposited– Skin pigmented– Adv. brain functions

Maternal Development

• 90% chance full term• Incr. mucosal secretions• Increase breast size• Pelvis spreads• Pressure on organs• Feel baby move• Indigestion & heartburn• By end: others can feel

baby

Third TrimesterFetal Development

• 28-31 wks– 15-16”, 3.5 lbs– Fully developed (except brain, lungs, liver)– Movements increase

• 32-36 wks– 17-20”, 5lbs– Synapse brain & nerves– Head down position– Adding fat

• 37-40 wks– 21-23”, 6-10lbs– Testes descend into scrotum– Receiving antibodies– When ready: placenta incr. estrogen,

increases oxytocin, stim contractions– Contractions start at top uterus and spread– Moves lower back into pelvis

Maternal Development• Back pain• Swelling• Itchy skin• Hemorrhoids• High bp• Visible kicks/punches• Increase in relaxin

production

Labor & Delivery• Dilation

– avg 15 hrs– Cervix dilates– Contractions 10 – 30 minutes– Amnion ruptures - “water

breaks”• Parturition: expulsion of fetus

– Less than 2 hrs– Cervix pushed open by fetus– Full dilation 10 cm – If canal is too small – Dr

performs episiotomy• Placental After-birth

– Less than 1 hr– Muscle tension in uterus and

shrinking of uterus tears placenta away from uterine wall, placenta is ejected (blood loss)

Premature Labor

• < 14 oz – underdeveloped, no chance of survival

• Between 25-27 weeks – may survive, but with developmental abnormalities

• 28-36 weeks - survival w/normal development

Multiples

• 1/89 Twins– 70% dizygotic – “fraternal” 2 eggs

fertilized at the same time– 30% monozygotic – “identical”

splitting of blastomere– Conjoined twins - incomplete

splitting of blastomere (share skin, liver, other organs)

• 1/7921 triplets