Congenital defects and human embryology Flashcards
What percentage of life births have some congenital defect?
20
Name some causes of congenital defects?
- No known cause
- Genetic
- Drug use
- Environmental
How does the drug accutane cause congenital defects?
Contains vitamin A which is fat soluble so can accumulate in the body. Toxic especially to developing foetuses
When do most major congenital defects occur?
First four weeks
How would you classify a major/ minor congenital defect?
Major: abnormality requiring medical/ surgical intervention
Minor: abnormality requiring no severe intervention and causing minor handicap
What is anencephaly
Without a skull
Skull bones don’t form so cerebral cortices exposed
Usually incompatible with life
What is hypospadias?
Penis not fused
Classified as major defect but not life threatening
Which is cryptorchidism?
Testes not in scrotum at birth
Minor defect
What is holoprosencephaly?
Abnormal forming/ incorrect size midline structures
What is congenital diaphragmatic hernia?
Gastrointestinal system enters thorax, usually on left side of diaphragm.
What is gastroschisis?
Body wall not closed, so intestine external.
Where does fertilisation occur
Ampulla of uterine tube
What happens in week 1 of development
Going through oviducts
1 cell–> morula (ball of cells) in first 4.5-5 days
Becomes a blastocyst when in uterus, before implantation
What day does implantation usually occur?
Day 6
What happens in week 2?
Differentiation of trophoblast, embryoblas and formation of 2 cavities
What does the trophoblast differentiate into in week 2?
Cytotrophoblast and synctioblast
What does synctioblast eventually form?
Placenta
What does the embryoblast differentiate into in week 2?
Hypoblast ventrally and epiblast dorsally
What 2 cavities are formed in week 2?
Amnioclast cavity dorsal to epiblast,
Yolk sac cavity ventral of hypoblast
What is hydatidiform mole
No foetus, only placenta forms
Usually occurs when no maternal nucleus- sperm has fertilised egg without nucleus
What are the karyotypes of partial hydatiform mole?
69XXX, 69XXY and 69XYY
What happens in week 3 of development?
2 layers of embryoblast are transformed into ectodern, mesoderm and endoderm.
Body axes are established
What does ectoderm become?
Skin and nervous system
What does mesoderm become?
Muscles, bone, connective tissue
What does endoderm become?
Lungs, gut
What is sirenomelia
Mermaid syndrome
Not enough mesoderm is produced at lower end of body bc epiblast cells stop invagination too soon leading to no separation between legs
What is situs inversus
Complete reversal of body organs
