ICL 4.7: Cardiac Development Flashcards
what are the steps of cardiogenesis?
- bilateral heart primordia
- primitive heart tube
- heart looping
- atrial and ventricular septation
- outflow tract septation (aorta and pulmonary trunk division)
slide 3
what is the first organ to form?
the heart! it forms by 8 weeks!
what is the highly sensitive period of development for the heart during embryogenesis?
3-6 weeks
what are the cellular origins of the heart?
cardiogenesis involves cellular determination, migration, and differentiation along with a series of critical morphogenetic events
cells from the anterior lateral plate mesoderm give rise to the precardiogenic mesoderm, which is fated to form the heart well before cardiac morphogenesis begins
the precardiac mesoderm constitutes a horse-shoe-shaped region of the mesoderm extending back on either side along the foregut – an inductive influence from the neighboring endoderm has been postulated to stimulate the early formation of the heart (slide 6)
how many types of cells are generated from the cariogenic mesoderm?
every single cardiac cell type is established by lineage
diversification of embryonic cells which arise from the
cardiogenic mesoderm!! so all the different types of heart cells come from the cardiogenic mesoderm!
so the endocardial endothelial cells, atrial myocytes and ventricular myocytes all comes from the cariogenic mesoderm!!
then the endocardial endothelial cells differentiate into cushion cells and the ventricular myocytes differentiate into purkinje fibers
what are the stages of development of the mesoderm?
- embryonic mesoderm
- paraxial, intermediate and lateral mesoderm
- lateral mesoderm divides into splanchnic (organs) and somatic (skin) mesoderm
so the heart will be developed from the lateral mesoderm, specially the splanchnic mesoderm!
which part of the mesoderm is the heart developed from?
splanchnic mesoderm!
the heart is derived from the splanchnic mesoderm as bilateral tubular primordia located ventrolateral to the early pharynx
the splanchnic mesoderm develops from the lateral mesoderm along with the somatic mesoderm
what is the cardiogenic plate?
an area of the splanchnic mesoderm anterior to the head process of the early mammalian embryo that subsequently gives rise to the heart
as the mesoderm begins to split into the splanchnic mesoderm
and somatic layers, a cardiogenic plate is recognizable in the
splanchnic mesoderm rostral to the oropharyngeal membrane
slide 13
what is the cardiac jelly?
thecardiac jellyis an acellular gelatinous matrix secreted by the myocardium which separates it from the endocardium in early heart development
the cardiac jelly surrounds the two bilateral primordial tubes which later fuse and they form the primitive cardiac tube – all of this is surrounded by the myocardium and epicardium
it permits shape changes needed for twisting and folding of the heart but as the heart tube matures, cardiac jelly gradually diminishes until the myocardium is adjacent to the endocardium
slide 14 and 15
what are the 4 layers that contribute to the wall of the heart tube?
- epicardium
- myocardium
- cardiac jelly
- endocardium
at this point the heart starts beating once the primitive heart tube is formed!
what are the parts of the primitive heart tube and what do they turn into?
- aortic sac
- truncus
- conus
truncus + conus = bulbus cordis –> right ventricle
this makes sense because the conus arteriosus is in the right ventricle!
- primitive ventricle –> expands to become left ventricle
- primitive atria –. fuse together to form common atrium
- sinus venosus –> right atrium
right now the right ventricle is separated from the right atrium by the left ventricle which is why the heart has to loop!
slide 18
what happens during looping of the heart?
The atrium and sinus venosus come to lie dorsal to the bulbus cordis, truncus arteriosus
and ventricles
slide 21
how does the heart wall form?
splanchnic mesoderm proliferates to form the
myocardial primordium
between the myocardial primordium and endoderm of the primitive gut, isolated mesodermal vesicles appear and fuse to form the endocardial primordium
cardiac jelly separates the myoepicardium from the endocardium – this layer gives rise to subendocardial tissue
slide 22/23
what happens during early partitioning of the heart? late?
EARLY PARTITIONING
1. formation of the atrial-ventricular canal
- formation of the endocardial cushions (valves)
- separation of the atrium from ventricles
LATE PARTITIONING
1. partitioning of the atria
- repositioning of the sinus venosus
- partitioning of the ventricles (L/R)
- partitioning of the outflow tract (aortic/pulmonary trunks)
what is the endocardial cushion?
endocardial cells lining the AV canal after the heart has looped undergo epithelial mesenchymal transformation and migrate into the cardiac jelly within the walls of the AV canal and the outflow tract
these transformed cells are now called cushion cells; they proliferate and differentiate into mesenchymal-filled bulges called cushion tissue or endocardial cushion
neural crest cells also migrate into the cardiac jelly of the outflow tract so the cushion cells and tissue in the outflow tract is formed from both endothelial-derived cells and from neural crest cells
3 pairs of endocardial cushions are formed: anterior, right/left, right/left conotruncal
slide 27
the endocardial cushions are what form the left atrioventricular canal!!!
slide 28