Embryology and Birth Defects Flashcards
What is spina bifida
Neural tube closure fails => cleft vertebrae
Describe the 2 main oesophageal abnormalities that may occur
Atresia-blockage
Fistula-oesophagealtracheal connection
What is lung aplasia
Lungs fail to form
What are the possible consequences of a malrotation
Gut blockage
- normally herniate, rotates, returns
- abnormal rotation =.> atresia
What is an omphacele
GI found outside the body
-fails to be reabsorbed after herniation
What is spondylocostal dysostosis
Normally 1 somite = 1 vertebrae
Abnormal somites = abnormal vertebrae
What forms from the lateral plate mesoderm
Heart, CV system, blood
Pleura, pericardium, peritoneum
Smooth muscle, vessels
Dermis, connective tissue
What forms from the intermediate mesoderm
Kidney
Gonads
What forms from the paraxial mesoderm
Somites
- back dermis
- trunk, limb skeletal muscle
- vertebrae, ribs
What 4 key structures form from the neural crest
Migratory cells
Cranial
-skull
-cranial ganglia
Vagal
- SM
- GI ganglia
- cardiac septa
Trunk
- SNS ganglia
- adrenal medulla
Sacral
- SNS ganglia
- GI ganglia
What is Hirschsprung’s disease
Bowel expansion due to lack of enteric ganglia
- abnormal vagal, sacral neural crest cells
- needed for peristalsis
What are the 2 categories of genetic factors that contribute to birth defects
Chromosomal
- aneuploidy
- deletions
Mutation
- protein function changes
- promotor/enhancer changes
What environmental factors contribute to birth defects
-TORCHSZ
-drugs
When is the risk the highest
Toxoplasmosis Other viruses Rubella Cytomegalovirus Herpes, HIv Syphillis Zika
Drugs
- valproate => spina bifida
- thalidomide => limbs
- alcohol => fetal alcohol
During the embryonic period = peak organ development
What is congenital adrenal hyperplasia
-how do the sigs and symptoms vary between females and males
21 hydroxylase non functional => cortisol and aldosterone can’t be produced
=> excess androgen production
Female
-virilisation of genitals
Male
-electrolyte imbalance => vomit, dehydration, arrhythmia
What is Liebenburg syndrome
Pitx1 gene normally => leg expression
promotor/enhancer => expression in arms => legalize arms
What is fetal alcohol syndrome
What are the signs and symptoms
Microcephaly
Low nasal bridge, short nose, small jaw, thin upper lip
Smooth philtrum
Mental defects
What is oligohydramnios
Not enough AF
=> bladder, kidney => fetus compressed
=> joint defects (MSK dev impacted)
=> lung damage (fluid leaks out from lungs, but is needed for its own protection
What 3 physical factors can lead to birth defects
Oligohydramnios
-not enough amniotic fluid
Amniotic bands
-constrict limbs
Uterine compression
What is the cut off for premature survival
Why is this
24wk
Surfactant production starts
-needed for lung function
Insufficient glycogen, fat, brown adipose
-accummulate in 3rd trimester
Retinopathy of prematurity
- eyes not developed
- high O2 scars retina => blindness
What happens on day 0
What happens on week 1
Embryogenesis begins
Cleavage and blastocyst formation -inner cell mass => embryoblast -outer cell mass => trophoblast Implantation -syncytiotrophoblast secretes HCG (detected on day 8-10)
What happens on week 2
What happens on week 3
What happens on week 4
Bilaminar disk formation
- 2 germ layers => epiblast and hypoblast
- 2 cavities => amniotic cavity and yolk sac
- 2 placental parts => cytotrophoblast and syncytiotrophoblast
- notachord forms
Gastrulation => endoderm, mesoderm, ectoderm
Initiation of heartbeat
Formation of 4 limb buds
Neural plate closes
What happens between week 3-8
- why is this the riskiest time
- what are the key points
Embryonic period
- major organs start development
- haematopoesis taken over by liver, thymus, spleen
- wk7 sexual differentiation
Most susceptible to teratogens
What happens at week 10-12
Sex of foetus is recognisable => phenotypic differentiation finishes by wk20
