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
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
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