Development of the CVS Flashcards
The heart tube has formed and is pumping by what day?
22
What happens at day 23 of the heart development?
Heart tube begins to fold due to differential growth
Folding of the heart take place across how many days?
6
What divides the common atrium
Septum primum: grows down from the superior atria wall
septum secundum
What is the hole in the septum primum?
ostium primum, then as the wall fully forms another hole arises = ostium secundum
What is the second wall to form in the common atrium, its hole and function?
septum secundum, hole = foramen ovale create a shunt for blood to flow from the right to left atria so blood can bypass the lungs
What is the fossa ovalis and how is it formed?
after birth pressure is greater in the L side of heart, pushing septum primum against septum secundum = fuse = leaving indentation in R atrium = fossa ovalis
How is an atrial septal defect caused?
failure in any stage of the septum primum and septum secundum fusing together
In development what separates the L and R ventricle?
muscular septum grows up to form the intraventricular septum, small shunt = primary intraventricular foramen – closed by endocardial cushion tissue growth
How is a ventricular septal defect caused?
failure of endocardial cushion tissue to close gap
During development how is a single outward flow tract divided into the aorta and pulmonary trunk?
endocardial cushions form in the truncus arteriosus and bulbus cordis in week 5, they fuse forming one spiralling septum, which divides outflow tract into pulmonary trunk and aorta
At what point in development do we see the heart structure that persists for the remaining uterine life?
5 weeks
What is the function of the ductus arteriosus?
blood vessel present in all babies while still in womb that allows blood to bypass lungs = flow from pulmonary artery to aorta
When the ductus arteriosus closes after birth what is this now called?
ligamentum arteriosum
When does the CVS start to appear and why?
middle of third week as embryo is no longer about to satisfy its nutritional requirement by diffusion alone
At what stage and what cell develop the primary heart field PHF?
migration of heart progenitor cells, ~day16
In the 4th week the heart undergoes cardiac looping, what is this?
heart folds on itself and assumes normal position in left part of thorax atria posteriorly and ventricles in an anterior position
What is dextrocardia?
failing of heart folding causes the heart to lie on the right side
What embryonic tissue gives rise to the CVS?
mesoderm
What is the most common birth defect?
congenital heart defect
What is the most common cause of indirect maternal death?
congenital heart defect
What is the cardiogenic field?
zone within the mesoderm, that start to diff into blood islands, that has the capacity to generate the entire CVS
How may blood islands are present?
2
A congenital defect can be classified as?
Structural abnormalities or complete absence of a structure
What causes congenital birth defects?
Genetic, exposure to chemicals/drugs/infectious agents, unexplained
What is a teratogen?
an agent or factor which causes malformation of an embryo
What is the added complexity of CVS devel?
system that works for the foetus but then changes and works after birth – able to switch
What is the primitive heart tube derived from?
a modified blood vessel
How is the primitive heart tube formed
2 endocardial tubes either side fuse when the embryo folds
How is the primitive heart tube divided?
5 regions:
1) aortic roots
2) truncus arteriosus
3) bulbus cordis
4) ventricle
5) atrium and sinus venosus
Why does the heart tube twist and fold?
As it grows it is limited in space by the pericardial cavity
What structures has the right atria devel from?
Primitive atrium, sinus venosus
What structures has the left atria devel from?
Small portion of primitive atrium, proximal part of pulmonary veins
What are the circulatory requirements of a foetal heart?
Lungs don’t work, O2/CO2 via placenta = shunts required to bypass lungs = HAVE to be reversible at birth
What is the path of foetal circulation
Oxygenated arrives at umbilicus, shunt bypasses liver (ductus venosus), to inferior vena cava, to RA, shunt, to LA (foramen ovale), LV, aorta, systemic – also: small amount of blood to RV (for devel) shunt from pulmonary trunk to aorta to bypass lungs (ductus arteriosus)
Even though the shunt between the RA and LA bypasses the lungs, why does a small amount of blood go to the RV?
Need to allow that RV to work against something to enable full devel
What is the duct that allows foetal blood to bypass the liver?
ductus venosus
What is the shunt between the RA and LA?
foramen ovale
What is the shunt from the pulmonary trunk to the aorta?
ductus arteriosus
The 4th arch in foetal devel is remodelled to?
R = proximal part of R subclavian artery L = arch of aorta
The 6th arch in foetal devel is remodelled to?
R = R pulmonary artery. L = L pulmonary artery + ductus arteriosus
Outline patient ductus arteriosus
Normally spasm closes the ductus arteriosus – but doesn’t close often in premature patients = persistent communication between pulmonary trunk and aorta = blood shunt L to R
What are the 2 components of a ventricular septum?
Muscular, membranous
Finish the table
