5 - Development of the heart Flashcards
What mesoderm does the heart develop from
Cardiogenic mesoderm of lateral plate
How does the heart structure develop
Blood islands - hemangioblasts (blood and blood vessels)
Angiogenic cells clusters for the right and left endocardial tubes at day 20
What are the endocardial tubes
Dorsal aorta, outflow tract
Vitello-umbilical vein and inflow tract
What day do the endocardial tubes fuse into the primitive heart tube
21
What forms the primitive myocardium
Mesoderm from foregut forms the external layer
What day does the heart beat on
22
What divides the atria from primitive ventricle
Atrioventricular suclus
What does the primitive ventricle become
Expands to become the left ventricle
What does the interventricular suclus divide
Primitive ventricle from bulbus cordis
What day does heart looping occur
22-24 days
What is dextrocardia
Anomaly where the primitive heart tube folds to the left (situs invertus)
On what day does the septum fform AV canal
Day 28
How does the septum form the AV canal
2 swellings of mesenchymal tissue appear from walls of the canal (endocardial cushions)
The cushoins grow and fuse together to divide canal into R and L
What is septum primum and when does it develop
Day 28
Divides R and L atrium
What is ostium premum
Osteium (opening) formed by free edge of septum primum
Ostium embryologY
• Perforations coalesce to form ostium secundum to the right of the first ostium.
• Right left shunting of blood via foramen ovale
• Septum primum acts as a valve
• Pressure increase in left atrium closes valve by fusing two ostium together
o Fossa ovalis in adult
Ventricular portioning
After 28 days, septum develops from floor (muscular) and grows towards membranous IVS (septum) which develops from endocardial cushions, IV foramen is a temporary opening which closes when muscular and membranous septa fuse at 7th week trabeculated appearance- diverticulum of the walls.
What separates the aorta and pulmonary trunk?
Trunctus arteriosus
What travels from baby to placenta
umbilical arteries (x2)internal iliac arteries, deoxygenated high pressure blood
What travels from placenta to baby
umbilical vein (becomes ductus venosus, oxygenated high pressure blood)
Foetal circulation
Reduced pulmonary blood flow
Ductus arteriosus from PT to Aorta(shunt)
Ductus venosus (continuation of umbilical vein)
Foramen Ovale (RA –> LA)
Function of ductus arteriosus
Allows RV to strengthen
High pulmonary vascular resistance
Protects lung against circulatory overload
Bypasses lungs
Ductus venosus
Connects umbilical vein to IVF
Regulated via sphincter
Conducts oxygenated blood
Will bypass the liver (80%)
Foramen ovale
Shunts highly oxygenated blood
RV pumps 2/3 cardiac output
Bypass the pulmonary circulation
