Week 3 Flashcards
(34 cards)
Infectious causes of congential anomalies
TORCHS.
Toxoplasmosis
Other agents
Rubella
Cytomegalo virus
Herpes
Syphillis
Causes secondary anomalies (external factors).
Primary = genetic
Nutritional causes of congenital anomalies
Iodine.
Folate.
Obesity.
Diabetes.
Excess vitamin A.
Enviromental causes of congenital anomalies
Pesticides.
Medications (anti epileptics).
Alcohol.
Tobacco.
Radiation.
Classification of embryogenesis disturbances
Polytopic field defect (2-4 wks)
- Scattered pattern (eg. trilaminar disc)
Monotropic field defect (4-8wks)
- Localized defect
Fetal period - Organogenesis (>9wks)
- defective organs
Polytopic field Defects
VACTERL
- Vertebral anomalies
- Anal atresia
- Cardiac anomalies
- Tracheo-oesophageal fistula
- Reneal anomalies
- Limb anomalies
Embryo = 2-4 weeks
Monotopic Field Defects
Cleft lip/palate.
Tracheo-esophageal fistula.
Holoprosencephaly.
Disruption anomaly example
Amniotic bands.
- strips of amiotic membrane around the fetus.
Poland anomaly.
- Interruption of subclavian artery vascular supply due to maternal use of cocaine. underdevelopment of pectoralis major on affected side.
Disruption = development started normal but then went wrong.
Sequence anomalies
Potter sequence.
- Renal agenesis > oligohydramnios> pulmonary hypoplasia > limb position defects
Pierre Robin sequence.
- Mandibular hypoplasia > tongue cannot drop > impaired palate development
Sequence = one problem resulting in a cascade of events
Di George Syndrome
Partial deletion of chromosome 22.
Characterized by a range of anomalies.
Includes failure of developement of 3rd & 4th pharyngeal pouch.
Syndrome = collection of SIGNS + SYMPTOMS
CHARGE syndrome
CHD7 heterozygous mutation.
Coloboma (eye defect).
Heart defects.
choanal Atresia.
growth & development Retardation.
Genital hypoplasia.
Ear defects.
single gene mutations typically involve transcription cofactors.
Spina Bifida
Defects in closure of caudal neural tube.
Can occur anywhere, most commonly in lumbosacral region.
Hydrocephalus nearly always occurs.
Neurological deficits can happen.
Fetal Alcohol Syndrome
Neural crest migration and brain development sensitive to alcohol.
1/100 births.
Smooth philturm. Thin upper lip. Small head. Flat midface. Small eye openings.
Congenital Rubella Syndrome
Fetus infected with rubella.
Infection affects development of organs of special sense plus heart and others.
Microcephaly. Cataracts. PDA (Patent Ductus Arteriosus).
Screening
When?
Pre-conception (genetic counselling).
Antenatal
1st trimester: Triple test, Nuchal fold
2nd (20wk): Anomaly scan
Newborn screening examination.
Fetal Circulation
Internal iliac artery > umbilical arteries > intervillous space in placenta > L umbilical vein > ductus venosus > inferior vena cava > right atrium > left atrium > L ventricle > aorta
Ductus venosus (liver bypass).
Ductus arteriosus (bypass lungs).
Formamen ovale (bypass right ventricle & lungs)
Parts of fetal circulation in adulthood
ie ligamentums
Ductus venosus - Ligamentum venosum
Ductus arteriosus - Ligamentum arteriosum
Umbilical vein - ligamentum teres
Umbilical arteries - medial umbilical ligaments
Forament ovale - fossa ovalis
Changes in circulation at birth
No placental return:
Decreased vascular flow in IVC = decreased flow to RA
Increased systemic vascular resistance
Increase LV workload
First breath:
Decreased pulmonary vascular resistance.
Increased left atrium pressure.
Septum secundum forced closed on septum primum = fossa ovalis.
Ductus Venosus
DV connects umbilical vein supplying oxygenated blood to the IVC.
Blood enters RA.
Bypassing liver, saturation is maintained (from 75 to 60%).
Foramen Ovale
RA pressure is higher than LA.
Forces FO to open and bloodflow to LA.
Free border of septum secundum forms crest - Crista dividens.
Creates 2 streams of blood flow.
Majority flow to LA.
Minor flows to RV where it mixes with blood from SVC (deoxygenated).
What causes closure of ductus ateriosus and venosum?
Increased oxygenation + reduced placental prostaglandin E2. Vascular spasm.
Ductus arteriosus closes 24-48hrs.
Ductus venosus closes more slowly.
Conditions causing duct dependent systemic circulation
- Coarctation of Aorta.
- Critical aortic valve stenosis.
- Hypoplastic left heart syndrome.
Blood flows pulmonary artery > aorta
- narrowing in the aorta
- aortic valve stenosis
- small LV
Conditions that cause duct dependent pulmonary circulation
- Pulmonary atresia
- Tricuspid atresia
- Critical pulmonary stenosis
- Tetrology of fallot
Blood flows Aorta > pulmonary artery
- Fused pulmonary valve - requires patent foramen ovale
- fused tricuspid - requires patent forament ovale
Ductus Arteriosus
Shunts from RV and PT to Aorta.
Minimizing drop in O2 saturation.
Development of Lungs
Week8-16: Pseudoglandular stage
- Duct system formation in the bronchopulmonary segment (Bronchioles).
W16-26: Canalicular stage
- Formation of terminal respiratory bronchioles.
W26-term: Terminal sac stage
- Terminal sacs begin to bud.
- Differentiation of Type 1 & 2 pneumocytes.
