Systemic embryology and congenital malformations Flashcards
Three layers in trilaminar embryonic disc
Ectoderm, mesoderm, endoderm
Parts of body from ectodermal germ layer
Skin/ear/nose/eye
Contact with outside world
How does neural tube form?
Ectoderm - neuroectoderm
3 parts of mesodermal germ layer
Paraxial, intermediate, lateral plate
What are neuromeres?
Somitomeres in association with neural plate
What do neuromeres do?
Contribute to connective tissue in head
What are somites?
Somitomeres on either side of neural tube
What are somites made from?
Paraxial mesoderm
At what rate do new somites appear?
3 pairs per day
How many somites formed at end of 5th week?
42-44
What does intermediate mesoderm form?
Urogenital system - primordial germ cells, gametes and gonads
What does lateral plate mesoderm split into?
Somatic (parietal) and visceral (splanchnic)
What does parietal layer do?
Lines body walls
What does lateral plate mesoderm form?
Skin, ribs, limbs, blood cells, blood vessels
What does endodermal germ layer form?
GI tract, bladder, urethra, auditory tube,
What is morphogenesis?
Form shaping process in embryo - differential tissue growth
What is dysmorphogenesis?
developing abnormally, outside arbitrary range
What is deformation?
Secondary morphologic defects that are imposed upon an organ or body part due to mechanical forces over a prolonged period - an indirect effect e.g. club feet
Symtoms of Down’s syndrome
- Trisomy 21
- Flat facial feature with small nose
- Reduced muscle tone (hypotonia)
- Upwards/downward slant to eye
- Large tongue that sticks out
- Single deep dcrease across palm
- Hyper-flexibility of joints
Symptoms of foetal alcohol syndrome
- Short palpebral fissure lengths
- Smooth philtrum
- Thin upper lip
- Brain damage
What is teratology?
Study of birth defects/congenital malformations
Where is inhibin A produced?
Foetus and placenta
Sacrococcygeal teratomas
Remnants of primitive streak persist and form tumours
Situs inversus
Transposition of visceral organs
Sirenomelia
Legs stuck together like mermaid
Caudal dysplasia
due to mesodermal insufficiency in caudal-most region of embryo which contributes to formation of lower limbs, urogenital system and lumbosacral vertebrae
- Affected child exhibits a variable range of defects including: hypoplasia and fusion of lower limbs, vertebral abnormalities, renal agensis, imperforate anus, abnormalities or genital organs
