Embryology of the cardiovascular system Flashcards
Summarise the stages of heart development
Linear heart tube formation
Formation of the cardiac loop
Heart septation
Cavitation of ventricle
Formation of valves and great vessels
4-chambered heart
How does the cardiac loop form
Which day does it occur on?
Ventricles and bulbus cordis grow faster than the other regions ;
The bulbus cordis moves forward, down and right, and the primitive ventricle moves backwards, up and left.
Occurs on day 28
What are the endocardial cushions ?
Localised swelling of outflow tract and AV canal
Crucial for valve formation and septation (separation of heart into chambers)
Describe the septation of the primordial atrium (4-6 weeks)
Endocardial cushions close up the primitive atrium
Septum primum grows downwards from the middle of the primordial atrium and fuses with endocardial cushions
Perforations form in the septum primum to allow blood flow through the primordial heart (higher presssure in right atrium than left pre-natally (as no blood is coming from the lungs yet)
Septum secundum grows now ; valve of foramen ovale forms now - this allow deoxygenated blood from vena cava to pass into LA and be pumped to the rest of the embryo whilst the ventricles are still not yet formed
How are valves formed?
From swelling of the endocardial cushions
Compare prenatal and postnatal circulation *
Prenatal blood is being supplied from the placenta via the foramen ovale (found on middle wall between atrial chambers) ; little blood goes to lungs as embryo is breathing in embryonic fluid not air - high resistance in lungs
Postnatally - Fossa oval is closed by valve of foramen ovale due to pressure changes from expansion of lungs
Septation of the primitive ventricle (5-20 weeks)
Formation of the great veins
Most of the wall of the LA is derived from the primordial pulmonary vein and its branches ; the primordial pulmonary vein is incorporated into the LA as it expands
The L horn of the SV becomes the coronary sinus and right atrium
The R horn also becomes incorporated into the R atrium to form the sinus venarum
Describe Latium secundum ASD (atrial septal defects)
opening in the middle of the atrial septum ; occurs when tissue of septum primum does not reach septum secundum so wall does not close off / or when a hole is left in the septum primum
The heart is derived from the …
Splanchnic mesoderm
Label the linear heart (Day 20)
2 tubes form in the mesoderm
They fuse then swell at the centre
The structure then twists in a rightward direction
what do the aortic sac, bulbus cordis, primitive aorta, primitive ventricles, sinus venosus all form?
Formation of the great arteries(outflow tract)
Endocardial cushion form within the TA and BC left to right and forwards to backwards ;
As the aorticopulmonary septum spirals as it forms , the aortic arch and pulmonary trunk twist around each other in a corkscrew fashion
Describe how embryological development lead to these features :
A)Internal walls of atria consist of smooth and rough areas
B)fossa oval is on middle wall between atrial chambers
A) incorporation of sinus venosus and veins into atria
B)derived from closure of foramen ovale
Describe the most common atrial septal defects
Ostium secundum ASD - foramen ovale doesn’t close ; seen as enlarged RA/RV/PA
