The document summarizes cardiac development and fetal circulation. During cardiac morphogenesis, the heart forms from clusters of cells on either side of the embryo that fuse to form the primitive heart by day 22. The heart then undergoes looping and septation to form the four chambers. In fetal circulation, blood bypasses the lungs via the ductus arteriosus and bypasses the liver via the ductus venosus to reach the placenta for gas and nutrient exchange. Blood then returns to the heart via the umbilical vein and inferior vena cava before mixing in the atria via the foramen ovale.

1. CARDIAC DEVELOPMENT & FETAL
CIRCULATION

2. CARDIAC DEVELOPMENT
 Cardiac morphogenesis
 Looping
 Septation
 Molecular development
 Functional development

3. 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

6. LOOPING
22-24 days to 28 ndays
Heart bends ventrally and
toward right
Outside appearance similar to
our heart

7. CARDIAC SEPTATION
 Inside appearance
 26 days

8. Atrium
Septum primum
Septum secundum
Ostium primum , ostium secundum
S.P + O.S = foramen ovale

9.  VENTRICLES
 INLET – primitive ventricle
 OUTLET – bulbus cordis
 conotruncal septum
 spiral septum aorta &
pulm artery

11. 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

12. MYOCYTE
MYOCYTE
• SIMILAR ISOFORMS
• MLC , ANP
VENTRICULAR
• MLC 2v
ATRIAL
• MLC2a
• ANP

13. FUNCTIONAL DEVELOPMENT

14. FETAL CIRCULATION

19.  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