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Flashcards in Embryo Deck (85)
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what is teratogenesis

Production of birth defects Malformations: non-reversible morphological defects present at birth Could be exterior or internally located or only microscopically visible Congenital anomalies = present at birth. >200 different congenital anomalies


What is the prevalence of birth defects



What is the leading cause if infant mortality and why

1/4 of deaths up to the age of 15 is due to birth defects due to structural and functional defects in vital organs and for the same reason 1/3 of children younger than 1 year Because: -Improvements in obstetrical (during and after delivery) care -↑ Medications and social drug use - Environmental contaminants?


Can you observe birth defects at birth?

No sometimes they do not show themselves until later ( like heart defects)


what are the causes of developemental defects

20-25% of the causes of birth defects due to known genetic causes and chromosomal aberrations. -Maternal illnesses (infections, metabolic disturbances) Drugs & chemicals


Is susceptibility is influenced by some factor

Susceptibility to teratogenesis heavily influenced by genetics of mother and infant.

Nutritional deficiencies play a significant role + genetic susceptibilities.


How many pregnancies end up with healthy outspring



For optimal pregnancy outcome what parameters you should have


Low birth weight can predict

Can be a prognostic of cognitive development , can prognose obesity, lung problems, cardiac problems, diabetes


What is the largest contributor to unsuccessful pregnancy

post implantation losses


what is the most vulnerable time of fetal development

Conception (formation of zygote) -: Implantation ->Ovum divide & differentiate= organogenesis (3-8 weeks of pregnancy)

Organogenic period = teratogenic period (max. vulnerability for fetus is 17 – 57 days post-fertilization)


why women need to take adequate folate at all times and how neural tube is connected to it

Neural tube closes within 28 days of gestation, where most women do not know they are pregnant => adequate nutrition (folate) is essential for women capable of becoming pregnant


Why organogenic period is the most critical period of life

•Cell organization, cell differentiation, and organogenesis all take place

•Maximal cell division and differentiation


what is hyperplasia and when does it occur


•↑ cell number

•Time of maximum vulnerability for teratogenic effects

•Day 17 to 8 wks after fertilization


what will happen if some factors interfere with the process of hyperplasia

Permanent reduction in cell number


hypertrophy and hyperplasia during pregnancy will lead to

Increase in cell size + cellular division


After hyperplasia ceases what period begins


•Risk for development of organ or biochemical malfunctions

•~ after 8 wks gestation



What is happening after ovulation until the blastocyte

Ovulation: ovum expelled by ovary into Fallopian tubes à ovulation and menstrual cycle must be normal.

Fertilization: sperm penetrated oocyte -> zygote.

Blastogenesis: zygote beings to cleave -> increase in cell number à morula.

-Cavity forms in center: blastocele. The entire structure is now called a blastocyst. (4th day)


2 cell types in blastocyst

-Blastocyst: 2 cell types: embryoblast (inside) and trophoblast (outside)

Trophoblast cells secrete proteolytic enzymes -> erode epithelial uterine lining.


How nutrients aand fluid are absorbed at this stage?

Fluid and nutrients absorbed by phagocytosis = histiotrophic nutritional phase (20-25 days).


What will rise from embryoblast and trophoblast

Trophoblast forms a cord of cells -> endometrium -> start forming the placenta

Embryoblast-> cells for the fetus


When entry to uterine occurs of blastocyst

4-5 days


What is pre-implantation period, when and what is happening

Pre-Implantation (Zygote, Blastocyst)

•< 1 week

•Increase in cell number but no increase in cell size


Is there any consequences if there are any toxicants are in mother's body

•Exposure to toxicants: no effect, slight decrease in growth or lethality

•Fate of cells not determined -> great restorative capacity

•Low susceptibility to teratogens and few developmental abnormalities

Pleuropotency of cells à exposure to toxic conditions causes either lethality or no effect

Also: decreased exposure to toxins due to poorer accessibility of the conceptus.


What period is 16 days post-ovulation and how does it occur

gastrulation - embryo development.

Day 14: inner cell mass starts to differentiate into different cell types.

Starts with the formartion of invagination (Henson’s node) in the future cranial area of the ectoderm ->  moves caudally -> primitive streak (important role in nervous system).

 starts at the head region


What is happening at 2-3 weeks of gestation

Gastrulation (2 – 3 Weeks)

1.Primitive streak = future axis of the embryo => 3 layers of the embryo

2.Then, neurulation: ectoderm differentiates into neural plate à neural tube

3.Mesoderm & endoderm cells migrate internally to form organs and tissues

•Cell migration through primitive streak


What 3 layers are fomed furing gastrulation (2-3 weeks)

•Ectoderm (Brain, CNS, Skin)

•Mesoderm (Voluntary muscles, CV and excretory systems)

•Endoderm (Digestive and respiratory systems, glandular organs)


Is fetus ssuspeptible to toxicants at 2-3 weeks

Yes, because rapidly developing


Neural plate rise, forming edges, this will contribute to->

Lateral edges will form 

Neural groove

Lateral edges: neural crest cells, precursors of CNS and contribute to face & skull.


What happens 27-29 days post-ovulation

-General shape of embryo established, heart starts beating

-Embryo < 1 inch and < 1oz

-Neural folds fused -> neural tube has segregated into head region + postcranial region

If neural tube not closed by day 27-> spinal bifida