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78 Cards in this Set

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The process whereby the cells of the blastocyst are translocated to establish three germ layers.
When pre-embryo?
Week 0 - 2 between fertilization and implantation (day 7-10)
What day does implantation occur?
Day 7-10
When embryo?
Week 3-8
Between implantation (2nd week) and 8th week after fertilization.
When fetus?
After 8th week of fertilization.
Average time of pregnancy
- Biological: from conception, 38 weeks.
- Clinical: from first day of last menstruation, 40 weeks.
- Societal perceptive: from moment of postive pregnancy/moment that someone should have get period: -2 weeks: 36 weeks.
What are presumtive signs of pregancy?
Possible indicators of pregancy.

- increase size and tenderness breasts.
- missing menstrual period
- darkening areola
- morning sickness.
What causes morning sickness?
Change in stomach function that causes nausea and usually goes away after a few weeks (between week 2-8).

- In 75% of pregnant women
- Theory: aversion from eating harmful (nausea-causing) substances in senstive first weeks.
- women with morning sickness lower rate of miscarriage
What are probably signs of pregnancy?
Indicators that, in all likelihood, a woman is pregnant.

- postive pregnancy test
- enlargment abdomen
- increased frequency of urination
- postive Hehar's sign
What is the Hegar's sign?
The softening of the uterine cervix.
Happens at 6th week of pregnancy.
What are postive signs of pregnancy?
- fetal heartbeat
- fetal movement perception
- visualization by ultrasound/fetoscopy
What do pregancy tests do?
At home: test for hCG (human chorionic gonadotropin) in urine that is produced by the placenta to maintain the uterine wall (similar bio activity as LH)
When can a hCG pregnancy test be used?
From day 15, or 1 day after menstruation should have occurd, after conception.
Name the stages of pre-embryonic development.
Fertilization -> mitosis: 2 blastomeres, more mitosis: 32-morula. To this stage the cells are smaller and smaller as they do not 'grow'.
Then: blastomeres, gastulation, embryonic phase
How long does it take for the cell to become a morula?
3 days.
How does the preembryo move to the oviduct and what does it enter the uterus?
Cillia in the oviducts in uterine direction.
Day 3-4.
What is a blastocyst and when does it form?
Around uterine entry 3-4.
A cell layer inside the zona pellucida (trophoblast) encapsulates a vacuole (blastocoel) and the inner cell mass.
What are the functions of the inner cell mass?
- give rise to tissue
- therapeutic application; embryonic stem cells.
Implantation, what (steps) and when?
6th day: uterus secretes proteases that dissolve the zona pellucida.

Inner cell mass end of trophoblast attaches to uterine wall.

Implantation starts: invades the uterine wall.

(preembryo was freely in uterus for 2-3 days)
What happens during the early phases of implantation?
1. trophoblast differentiate into syncytiotrophoblast (outside) and cytotrophoblast (inside).
2. syncytiotro. secretes proteases -> penetration of uterine wall.
3. Deciduoma response of uterine cells.
Characteristics of syncytiotrophoblast?
- Secretes proteases
- Consists of a mass of cells that lost cell membranes -> communicating cytoplasms: A SYNCYTIUM.
- Sinusiods with maternal blood develop in syncytiotrophoblast.
What is the deciduoma response?
The uterine stroma devides rapidly and encapsulates the pre-embryo.
What are the physiological uterine requirements for implantation?
- primed with right pro/est levels secreted by the corpus luteum.
- endometrium has become more vascular, secretory and ready for implantation.
- pro: stimulate protease secretion.
When does implantation occurs?
Day (7-) 10.
Do the blastocyst and endometrium communicate with each other?
Of course. Signalling molecules are released from blastocyst.
Other physiological changes of preembryo during implantation?
- Amniotic sac
- Blastocoel becomes yolk sac
What happens at day 0?
What happens at day 3:
What happens at day 5?
Late blastocyst.
What happens at day 6?
Zona pellucida dissolved and preembryo attaches to endometrium.
What happens at day 7?
Implantation begins.
What happens at day 8?
- Amniotic cavity forms
- Embryonic disc appears
What happens at day 9?
Uterine sinusoids develop.
What happens at day 10?
Implantation complete.
Are HLAs found on placental cells?
No. Surprisingly, the fetal cells do not hav HLA. Might explain to s ome extend the lack of immune reponse to the fetus.
What happens during embryonic development?
Inner cell mass cells differentiate in bilayered disk:
- Hypoderm
- Epiderm
What does the hypoderm develop in?
Development of extraembryonic membrains, though these also have cells from trophoblast and epiblast.
What does the Epiderm develop in?
three layers:
- Ectoderm
- Endoderm
- Mesoderm
What are the four extraembryonic membranes?
- Yolk sac (not functional)

- Amnion (supports + protects from mechanical shocks, provide water and materials)

- Allantois (pouch at posterior end of embryo)

- Chorion (derived from cytotrophoblast, fuses with amnion eventually)
Ectodermal layer orgin
- Nervous system
- Epidermis of hair, skin, tooth enamel)
Endodermal layer orgin
all that are derived from embryonic gut tube:
- repiratory system
- digestive tube
- gal
- bladder
- pancreas.
Mesodermal layer orgin
The rest. Skeleton, muscle, circulatory stem, gonads, kidney, deeper layers of skin, notochord (becomes vertebral column)
What are the functions of the placenta?
- Repiratory (O2, CO2)
- Nutrient (O2, glucose, GFs, other things)
- Excecretory
Size of molecular barrier?
500 molecular weight.

(Later in pregnancy: maternal Abs actively pumped into blood stream.)
How many veins and arteries and what direction?
2 arteries (fetus -> mother)
1 vein (placenta -> fetus)
Placenta development
- 14th day: cytotrophin finger-like projections extend through the syncytiotrophoblast to the uterine stroma.

- syncytio surrounding villi secrete enzymes -> capillaries dissolve -> mothers blood forms sinoids that bathe the villi.

And voila: the placenta.
CHORIONIC VILLI (derived from the (cyto)trophoblast that surrounds the embryo and forms the chorion.
Why is the placenta called hemochorial placenta?
chorion villi bathing in maternal blood filled sinuses.
How does the mass of the placenta change over time?

(w. 4, 20, 40)
Week 4: covers 20% of uterine wall

Week 20: covers 50% and weighs 200 grams (fetus: 500)

Week 40: 700 gram, with 285 liter of blodd every day.
How does the endometrium change during pregnancy?
The endometrium becomes the decidua.

- decidua basilis: maternal part placenta

- decidua capsularis: overgrowth during the deciduma reponse.

- decidua parentialis: not directly covered.
What is the umbilical cord?
- Connects fetus to placenta
- derived from body stalk (which connected embryo to the chorion)
- Length: 20-22 inches and 03-1 diameter
Vessels etc in umbilical cord?
2 arteries, 1 vein. Embedded in Wharton's Jelly.
Types of twin pregnancies?
Dizygotic, monozygotic
Different 'types' of dizygotic twins?
Implant close together: share placenta, fused chorion.

Implanted further apart: separate placentas, chorions and amnions.
How do monozygous twins develop?
Inner cell mass in blastocyst devids.

Rare: morula divides. Then: separate amnions, chorions and placentas (or fused placenta if implanted closely to eachother.
What happens during embryonic development?
Major organic internal and external structures take place. Therefore, highly sensitive to disturbances leading to death or congential malformations.
Week 3 of embryonic development:
- embryonic disc begins to curl
- neural tube
- somites/lumps lining neural tube
Week 4 of embryonic development:
- C- shape
- pharyngal arches develop in next -> develop in jaws, ears, etc.
- eyes
- inner ear development
- heart forms and beating starts
- limps buds
Week 5 of embryonic development:
- arm buds develop more (flatten + paddle shape)
- 1 cm.
- brain grows rapidly
Week 6 of embryonic development:
- eyes pigmented
- exterior ears
- leg buds develop more (paddle shape)
- hand: position of digits
- tail present
- Brain/head continues to grow
Week 7 of embryonic development
- toe rays
- rapid development gut tupe -> protrude through umbilical cord -> umbilical herniation
- Tail gone
What develops earlier, arms or legs?
Arm buds (week 5) develop earlier than legs (week 6)
Week 8 of embryonic development
- fingers, toes, with thing sheet of webbing
- tail dissapeared
- brain, spinal cord, perihperal nerves developed
- end week 8: 1.25 inces
When does the fetal period start?
Week 9 (till birth).

Organ systems are establish and mainly foccused on developing, differentiate and GROOOOWING!
Week 12 - end of trimester
- fetal heartbeat with steoscope
- reacts to stimuli and movements begin (though too little to feel)
When does the mother begin to feel movements?
4-5 months
End 6th months/2nd semester
- skin covered with vernix caseosa: protective layer of fatty sexretions

- lanugo on skin: downy hair
3rd trimester
- lungs mature (main problem for premies)
- layers of fat added + wrinkles dissapear.
Youngest premature infant ever:
21 weeks. Most dont survive
Fetal circulation system
1. Enters at RA
2a. goes through foramen ovale
2b. enters RV and trhough ductus arteriosis to aorta
Fetal miscarriages
50% before prengancy is known

15% after pregnancy is known
Causes of fetal miscarriages/disorders
- Chromosomal abnormalities in 42%
(and occur in 1/200 newborns)

- Viruses/bacteria (CHECK WHICH ONES)

- teratogens, mutagens, etc.
Especially during week 4-7
Fetal evaluation and monitoring
(and what does the method check for)
- Ultrasound (heart beat week 8)
Checks: fetal anatomy and movement, placenta position.

- serum marker tests: Est, alpha-fetoprotein, hCG. Can estimale likelihood of Down Syndrom.

- Amniocentesis (w. 14-16)
chromosomal abnormalities

- chorionic cillus sampling
CVS vs. amniocentesis
- CVS: larger risk of miscarriage
- chorionic cells vs. amnionic fluid (and cells there)
- results back earliers
- CVS can be preformed earlies: week 8-10 vs 14-16
Abortion - when
- 1st trimester
- second trimester
- 3rd trimester (but not legal in US)
How is abortion induced in 1st trimester
1. Embryonic period abortion: medically with prostraglandic and mifeprisone (blocks progresterone receptor)
Another method for 1st trimester abotrions
Vacuum aspiration.

5 - 11th week

Vacurette tube inserted and coupled to suction devise. Not completely removed -> scrape endometrium.
1st trimester 3rd option
Dilation and curgette

Weeks 8 - 14th

Cervix is dialated with laminaria (seaweed thing), endometrium scraped witha curette
2 options for 2nd trimester abortions
1. Laminaria dialation and intramniontic administration of glucose, saline, urea or prostaglandin. Terminates pregnancy and induces delivery.

2. Dilation and evacuation
after 12th week.
dilation and then uterine content removal by suction, curette and forcepts.