CARDIAC DEVELOPMENT & FETAL
CIRCULATION
CARDIAC DEVELOPMENT
Cardiac morphogenesis
Looping
Septation
Molecular development
Functional development
CARDIAC MORPHOGENESIS
18 DAYS -
vasculogenesis .. Cell
clusters on either side of
embryonic axis
22 days – fuse –primitive
heart
Splanchnic mesoderm
forms myocardium&
myocardial jelly
Migrating mesothelial
cells-epicardium
HEART STARTS TO
CONTRACT
LOOPING
22-24 days to 28 ndays
Heart bends ventrally and
toward right
Outside appearance similar to
our heart
CARDIAC SEPTATION
Inside appearance
26 days
Atrium
Septum primum
Septum secundum
Ostium primum , ostium secundum
S.P + O.S = foramen ovale
VENTRICLES
INLET – primitive ventricle
OUTLET – bulbus cordis
conotruncal septum
spiral septum aorta &
pulm artery
MOLECULAR DEVELOPMENT
CARDIAC DIFFERENTIATION
ENDODERM-INDUCTION OF MESODERM SIGNALS
FGF ACTIVIN
INSULIN
TRANSCRIPTIONS FACTOR S
GATA4 MEF2
NKX
BHLH
RETIONOIC ACID RECEPTOR FAMILY
RECEPTO
RS
MYOCYTE
MYOCYTE
• SIMILAR ISOFORMS
• MLC , ANP
VENTRICULAR
• MLC 2v
ATRIAL
• MLC2a
• ANP
FUNCTIONAL DEVELOPMENT
FETAL CIRCULATION
the dorsal aortae develop at the same time as the early heart tubes. These connect to the heart tubes prior to fusion via the first aortic arch arteries. Other arches develop, which go on to form the arteries of the head and neck. We also previously saw the way in which the aorta and pulmonary trunk form. The dorsal aorta gives off branches which supply blood to the rest of the embryo:
Gut (ventral/front) branches
Lateral (side) branches
Intersegmental arteries
Fetal Circulation
As the embryo progresses to a fetus the vasculature is still remarkably different to that of the adult, including the presence of three vascular shunts:
foramen ovale (seen previously) - blood travels from the right atrium to the left atrium
ductus venosus - blood from the umbilical vein bypasses the liver to enter the inferior vena cava
ductus arteriosus - blood passes from the pulmonary trunk into the aorta
These shunts allow blood to bypass the lungs, liver and kidneys, whose functions are performed by the placenta while in utero.
The following diagram shows the movement of blood throughout the fetal circulation. The main flow of blood is as follows:
Placenta → umbilical vein → ductus venosus → inferior vena cava → right atrium → foramen ovale → left atrium → left ventricle → aorta → hypogastric arteries → umbilical arteries → placenta. Blood that passes from the right atrium to the right ventricle travels:
Right ventricle → pulmonary trunk → ductus arteriosus → aorta
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