Embryology and anomalies Flashcards
Fertilisation/implantation
Gamete fertilised @ ampulla -> oocyte meiosis II -> diploid conceptus
Cleavage (mitosis) -> blastomere -> throphoblast & embryoblast
D6 implantation - decidua reaction by stroma differentiate to decidua cells, increase stromal glands, vascularity
Embryo formation
Wk 2 - Bilaminar germ disc
- trophoblast invasion of spiral arterioles in decide basalis, vascular remodelling by 3 months
- D17 tertiary villi developed and fetal vessel present
Wk3 - gastrulation into Trilaminar germ disc (epiblast migration to mesoderm)
Wk 4 - neural plate formed by ectoderm
Neurulation by plate folding -> bidirectional closure from center
NTD
Incomplete closure of vertebrae at L5/S1
RFs: AED, hyperthermia, DM, obesity, prev NTD
4% recurrence
AFP - detect 80-90% of open NDT/anencephaly
Folate use 70% reduction
fortification 40%
USS findings:
Spine anomaly
Hydrocephalus/ventriculomegaly
Lemon shaped head
Banana Cerebellum
Chiari II malformation (cerebellm herniation through foramen magnum)
Lung development in utero
Endoderm - resp epithelium
Mesoderm- vascular/muscle
Repetitive branching of bronchial and pum. vessel tree
Embryonic - lung bud
Pseudoglandular <16/40 - branch to terminal bronchioles
Canalicular - 16-26 -> resp bronchioles develop
Saccular - 26-36 -> primitive alveoli
resp epithelium (T1 pneumocyte) thin out to capillaries able gas exchange
Alveolar >36 - maturation of alveoli, increase surfactant by T2 pneumocyte
Lung anomalies
Pulmonary hypoplasia - reduce terminal air sacs
2nd to - CDH, oligo, neuromuscular disorders, space occupying lesions
Congenital diaphragmatic hernia
L 80%
Diaphgram discontinuation w/ abdominal content hernia to chest
Asso. cardiac defect, poly, hydrops
Cardiac
Wk 4 - primitive heart tube
Wk 8 - completed loop/remodel and septation to 4 chambers
CHD
Incidence 1%
20% of all congenital defects
Antenatal detection:
1/3 of all, 80% of critical forms
Other methods:
NT> 3.5 - 3 fold, NT> 5.5 20%
Abnormal maternal serum markers in T2 - 2 fold increase
Heart tube defect: dextrocardia
Septal detect - VSD (25%), ASD, AVSD
Outflow defect - Persistent truncus arteriosis (incompelete separation of aorta and palm a)
Transposition of great vessels (cyanotic, L vent w/ pulm circle, R vent w systemic circulation)
TOF - VSD, overriding aorta, R vent hypertrophy, pulm stenosis (most common cyanotic)
GIT
Endoderm - embryonic folding
Omphalocele
ventral wall defect involve umbilicus, organ hernia
Covered with amnioperitoneal sac
Asso chromosomal T13/18, 50% cardiac
Physiological herniation of organs into umbilicus before week 12, however failure to refract
Recurrence 1%, high if syndromic
Gastroschisis
Asso. FDIU/FGR in T3
RF: young mum, smoker, drug use
4% recurrence
Defect of paraumbilical ventral abdominal wall, not involve umbilicus, bowel hernia
Failure of lateral fold closure
Fetal circulation
4 shunt system
Placenta - 40% CO
DV - UV to IVC by pass liver with O2 blood
DA - pulm a. to descending a. by pass lungs
FO - R to L atrium by pass lungs
Uterus flow - 600mls/min
Characteristics:
HbF higher O2 affinity - left shift of O2 dissociation curve
Single circut - by pass lungs
Higher PO2 at proximal than distal to DA
Lower vascular resistance and higher HR
Hypoxia reflex - rise BP, lower HR, increase flow to brain/heart, decrease to gut/lung/somatic
Fetal growth
Proliferation in early phase with organ maturations
fat accumulation from 32/40
Ongoing cerebral cortex/renal glomeruli growth near term
Fetal activity: Quite sleep, REM sleep, quite awak,e active awake
Hypoxia response
Acute hypoxia
- detect CO2 rise in chemoreceptor
- increase sympathetic response & catecholamine
- rise in HR and CO, activate anaerobic metabolism
Chronic hypoxia
- decrease growth and movement - glycogen use in liver small AC, reduce movement
- shutn blood to brain/heart - brain sparing
- reduce flow to kidney (oligo, less fluid more susceptile to cord compression)
Neonatal physiology
1st breath -> alveolar expansion, air filled lungs push fluid out -> reduce pulm vascular resistance
PO2 dilates pul vasculature
Pulm blood flow increase
Closure of shunts
- inability to expand lungs -> increase pulm HTN
Cardio:
Umb A. closure -> increase peripheral resistance
Umb V and DV closure -> perfuse liver
FO close - increase pulm return to lung, L atrium > R atrium pressure
DA - reverse flow due to rise in systemic resistance, fall in pulm resistance, high PO2 and fall in PG cause DA contraction -> ligamentum arteriosum
PDA - high PG in preterm hence L to R shunt, treat with NSAIDS, coil occulsion
Resp:
1st breath, alveoli expansion
Surfactent reduce surface tension keep open
* lack surfactent -> widespread atelectasis
Temp:
Inability of voluntary control
Large surface area to body weight increase radient heat loss
Wet - evaporation
Low fat store, head production by oxidation of brown fat
