Cardiac embryology and CHD Flashcards
Give an overview of the timeline of development in the heart
-tube formation day 15-20
-looping day 20-28 (1.5-3mm)
-Atrial septation day 34-50 (4-16mm)
-outflow tract septation day 35-56
-ventricular septation day 38-45
-development of cardiac valves day 35-56
Describe the tube formation structure and what the primitive structures become as the heart develops
To aortic arches
-trunctus arteriousus (aorta+PA)
-bulbous cordis (ventricle outlet)
-primitive ventricle (ventricle inlet)
-atrioventricular canal
-primitive atrium (RA +LA)
-sinus venosus (RA)
Describe tube formation
-initially from the mesochymal cells known as angioplastic tissue form a plexus of endothelial vessels which fuse to form two longitudinal cellular strands called cardiogenic cords.
These cords are cannalised and channeled to form two thin wall tubes called the endocardial and myoepicardial tubes which come together to form a single straight tube around day 22
-Space around the tubes eventually forms the pericardial cavity
Tube elongates and starts taking on various deliniated dilatations and constriction partially due to the confined space in the pericardium
Define plexus
an intricut network
When does the primitive heart have a recognisable pulse?
day 22-23
describe looping day 20-28
-restrictions from the pericardial space force the heart tube to bend/loop in a U shape
-the result of the looping is the atria and sinus venosus above and behind the ventricles
atria and sinus venosus behind the truncus arteriosus, bulbous cordis and the ventricle positioning the primitive LA and RA above the primitive LV and RV
Describe atrial septation day 34-50
septation of the atria, ventricle and atria canal begins within 4-6 week which involves the process of septa growth within the atria
the septum primum begins as a rigid tissue on the roof of the superior aspect of the common atria, the ridge develops by growing downwards into the atrial cavity leaving a gap between the endocardial tissue and septum edge
This gap/hole is known as the ostium primum which allows blood to flow across the atria and as time passes it begins to change
Septum secundum grows downwards and then up forming the septum secundum and the hole is the ostium secundum. We have a small flap called the foramen ovale allowing blood to flow across the right side to the left side
Describe septation of the ventricles day 38-45
-approx 4 week the primitive ventricle begins to grow leaving a small ruscular ridge which becomes the IVS
IVS is primarily formed by the dilitation of the two ventricles rather than the growth ( ventricles grow out and round making the muscular septum more prominant however overtime it grows up towards the endocardial cushions)
-Over time the superior part of the IVS grows towards the endocardial tissue becoming the membranous part of the VS
Describe outflow tract septation day 35-56
-bulbous ridges grow out from the endocardial cushion and fuse spiraling by 180 degrees which eventually become the aorta and PA
Describe the development of cardiac valves day 35-56
-creation of the two AV canals surrounding the subendocardial
-subendocardial grows out and inferiorly
-programmed cell death (apoptosis) creates sculpture in the leaflets ( carving out trabeculations and papillary muscles)
-pre-exervation stage- bulbous outgrowth/ swelling
-exervation stage-programmed cell death
-differentation between TV and MV
-after aorta pulmonary septum outgrowths of subendocardial tissue, we have programmed cell death from the tissue to form semi lunar cusps
Describe foetal circulation
-blood flow moves from the placenta through the umbilical veins towards the hepatic circulation
-passes the physiological shunt called the ductus venosus arriving in the IVC (oxygenated blood) ductus venosus allows it to bipass the hepatic circulation arriving at the IVC into the RA
RA blood moves directly across the formen ovalis pushing deoxy blood from RA to LA where its oxygentated, once it leaves the LV it goes out and up throught the aorta where it meets the connection between the PA and aorta ( ductus arteriousus)
that blood circulates aorund the foetas to exremities back to the placenta by umbilical arteries ( deoxy blood to placenta)
High pressure pulmonary circuit become we dont want much blood to the lungs as they aren’t functioning )
Low pressure systemic circulation in parellel with a low resistance
