Fertilization Study Essay

Submitted By dhinds09
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Pages: 16

Fertilization
Only one sperm will penetrate egg to initiate fertilization
Egg Able to live up to 24 hours
Sperm able to live up to 72 hours
Zona reaction: Membrane becomes impenetrable to other sperms b/c one sperm successfully penetrated the membrane
Egg and sperm fusion
Team effort to get to the egg, once the sperm gets to the egg, the other sperm backs off
Whole structure of the developing embryo is known as the blastocyst
Outer layer of cells surrounding the blastocyst cavity is the trophoblast
Implantation
Blastocyst embeds in the endometrium, by day 10 after conception the trophoblast secretes enzymes that enable it to burrow into the endometrium until the entire blastocyst is covered
Zygote---- Embryo by 8 weeks (embryonic stage is the most critical time in the development of the organ systems
Teratogens are less likely after 8 weeks, but still possible
Placenta Development
Begins to form an implantation
Maternal-placental-embryonic circulation is in place by day 17, when the embryonic heart starts beating
Endocrine gland that produces hormones necessary to maintain pregnancy hCG- can be detected in the maternal serum by 8 to 10 days. (basis for pregnancy tests) hCS/hPL- stimulates maternal metabolism to supply nutrients needed for fetal growth
Progesterone- maintains the endometrium, decreases contractility of the uterus, development of breast alveoli
Estrogen (7wks after fertilization) - stimulates uterine grown and uteroplacental blood flow. Estrogen increases greatly towards the end of pregnancy
Placenta function
Metabolism
Exchange of O2 and CO2
Transportation of nutritive factors and waste
Defensive
2 arteries and 1 vein Arteries- deoxygenated blood Vein- oxygenated blood
Teratogens Effects
A lot of key development happens by week 9-12
First trimester up to the first 12 weeks(3months)
Physiology of fetus
Circulation- mother help is very important
Embryonic Tissue Layers- may let you know where the malformation occurred Ectoderm
Brain, nerves, skin
Mesoderm
Cartilage, muscle, blood vessels, heart, kidneys
Endoderm
Digestive tract, respiratory tree, liver, pancreas
Gestation
Carrying of embryo or fetus
Time of conception to birth approx. 9 months (280 days/40 weeks)
Full term (37-42 weeks) after 42nd week will induce labor
Preterm (less than 37 weeks)
Trimesters
1st trimester (LMP to week 12)- most rapid changes occur during the FIRST TRIMESTER
2nd (13th-27th) – increase in size of fetus, refinement of human features
3rd (28th to 40th) Growth and preparation for birth
Fetal development at 4 week- usually get positive result by week 4
Can see the heart, eyes, liver, arm bub, brain
Fetal development at 8 week- key organs developed around this time/ embryonic period ends
Size of grape
Head is 50% of body
3cm long and weighs 2gm
Less susceptible to teratogens but still take precaution
Ossification begins
End of embryonic period
Fetal development at 12 weeks
Fetal heart beat can be heard with a Doppler
Sex distinguishable
Fetal development at 16 weeks
Can definitely know the sex
Baby is more active (quickening) fetal movement
Eyes can blink, baby should have fingerprints
Fetal development at 20
Should be 4cm in length
Should be below belly bottom
Some fetal testing can be done
Vernix caseosa appears
Lanugo appears
Fetal development at 24 weeks
Baby may be viable
May weigh a pound to a 1 ½
Fetal development a 28 weeks
Lungs are more mature, however if born lungs are not as strong
Are able to survive because of today technology
Fetal development at 32 weeks
Weighs almost 4 pounds
Skin has less wrinkles, fat starts to form under the skin
Will gain up to HALF its birth weight between now and delivery
Fetal development at 36 weeks
Lanugo disappearing
Skin pink, body rounded
Fetal development at 40 weeks
Skin smooth and pink, scant vernix caseosa, moderate to profuse hair
Active, sustained movement

Chapter 9 Infertility
As we age fertility goes down in women > 40- less viable eggs
Female Infertility
Number one…