For study purpose only.

1. EMBRYOLOGY CVS – PART I
CVS Embryology
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2. EMBRYOLOGY : CVS
• 1st system to function in embryo
• Circulation of blood : 3rd week
• Derived from mesenchyme
CVS Embryology
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3. EMBRYOLOGY : CVS
• Mesenchymal cells in splanchnic mesoderm proliferate &
form cell clusters : Angiogenic clusters
CVS Embryology
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4. EMBRYOLOGY : CVS
• Angiogenic cell cluster

5. EMBRYOLOGY : CVS
cephalic
•
Angiogenic clusters on lateral side then
spread rapidly in cephalic direction
caudal
CVS Embryology
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6. EMBRYOLOGY : CVS
• Angiogenic clusters form horseshoe shaped plexus of blood vessels
• Anterior central part of plexus : Cardiogenic area
CVS Embryology
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7. EMBRYOLOGY : CVS
Heart Development
• Develops from splanchnic mesenchyme in cardiogenic area.
CVS Embryology
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8. EMBRYOLOGY : CVS
 Cardiogenic area

9. EMBRYOLOGY : CVS

10. EMBRYOLOGY : CVS
 The Pericardial cavity

11. CVS EMBRYOLOGY
Bilateral cardiogenic cords:
• Formed from mesenchyme
• Cords canalized
• Form paired endocardial heart tubes
CVS Embryology
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12. CVS EMBRYOLOGY
• Endocardial tubes fuse into single heart tube forming primitive heart
CVS Embryology
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13. CVS EMBRYOLOGY
Fusion of primitive heart tubes

14. PRIMITIVE HEART
• Heart tube elongates & bends
• Cephalic portion : bend in ventral & caudal direction & to right
• Caudal portion : bends to left
CVS Embryology
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15. PRIMITIVE HEART
• Bending creates cardiac loop
CVS Embryology
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16. EMBRYOLOGY : CVS
• The cardiac loop

17. EMBRYOLOGY : CVS
Future heart develops dilatations & constrictions : results in 4 chambers:
• sinus venosus
• primordial atrium
• primodial ventricle
• bulbus cordis
CVS Embryology
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18. EMBRYOLOGY : CVS
Sinus Venosus
• Maintain paired condition longer
than any other portion of heart
tube
• Each horn receives the vitelline v,
umbilical v, common cardinal v
ACV: Anterior cardinal vein
PCV: Posterior cardinal vein
UV : Umbilical vein
VIT: Vitelline vein
CVS Embryology
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19. EMBRYOLOGY : CVS
Sinus Venosus
Sinus venosus receives:
• umbilical veins from the chorion.
• vitelline veins from the yolk sac
• common cardinal veins from the embryo.
CVS Embryology
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20. EMBRYOLOGY : CVS
Sinus Venosus
Inferior portion of right sinus
develops into 2 parts:
• Valve of inferior vena cava
• Valve of coronary sinus
CVS Embryology
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21. EMBRYOLOGY : CVS
Sinus Venosus
• Wk 4 consist of small transverse
portion & L & R sinus horns
CVS Embryology
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22. EMBRYOLOGY : CVS
Sinus Venosus

23. EMBRYOLOGY : CVS
Sinus Venosus

24. EMBRYOLOGY : CVS
Sinus Venosus
• At 1st communication between sinus & atrium is wide
• With obliteration of the left umbilical vein , the left sinus
horn loses its importance
CVS Embryology
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25. EMBRYOLOGY : CVS
•
Sinus Venosus
develops a left horn which becomes the coronary sinus & a right horn which will be incorporated
into right atrium
CVS Embryology
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26. EMBRYOLOGY : CVS
Sinus Venosus
Remnant of the left sinus venosus :
• Oblique vein of left atrium
• Coronary sinus
CVS Embryology
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27. EMBRYOLOGY : CVS
• Bulbus cordis & ventricle grow faster
CVS Embryology
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28. EMBRYOLOGY : CVS
• Heart bends upon
itself, forming a
bulboventricular loop
CVS Embryology
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29. EMBRYOLOGY : CVS
• bulboventricular loop
CVS Embryology
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30. EMBRYOLOGY : CVS
• Intro to atrium & sinus
• Atrium & sinus venosus come to lie dorsal to bulbus cordis, truncus arteriosus &
ventricle
• At the same time, heart invaginates into pericardial cavity
• Dorsal mesocardium which attaches it to dorsal wall of pericardial cavity degenerates &
forms tranverse pericardial sinus
CVS Embryology
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31. EMBRYOLOGY : CVS
Truncus Arteriosus
Truncus Arteriosus
• Continues caudally with bulbus
cordis
• Enlarges cranially to form aortic sac
from which aortic arches arise
CVS Embryology
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32. EMBRYOLOGY : CVS
• Enlarges cranially to form aortic sac
from which aortic arches arise
Truncus Arteriosus

33. EMBRYOLOGY : CVS
THE ATRIA
Fate of adult Left Atrium
• Formed by incorporation of primitive pulmonary veins
• As atrium enlarges, parts of vein & its branches absorbed
CVS Embryology
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34. EMBRYOLOGY : CVS
•
Primitive pulmonary vein & its 4 main branches become partially incorporated into left atrium = 4
pulmonary veins.
CVS Embryology
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35. EMBRYOLOGY : CVS
Result
• 4 pulmonary veins entering adult left atrium
• Smooth walled part of left atrium derived from absorbed pulmonary vein tissue
• Left auricle derived from primitive atrium
CVS Embryology
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36. EMBRYOLOGY : CVS
 Development of the smooth-walled portions of the right and left atrium.
 Both the wall of the right sinus horn (blue) and the pulmonary veins (red) are
incorporated into the heart to form the smooth-walled parts of the atria.

37. EMBRYOLOGY : CVS
Cardiac septation
 End of 4th wk, 2 mesenchymal cushions, the atrioventricular endocardial cushions,
appear at the superior and inferior borders of the atrioventricular canal
 In addition, 2 lateral atrioventricular cushions appear on the right and left borders of the
canal

38. EMBRYOLOGY : CVS
Cardiac septation

39. EMBRYOLOGY : CVS
Cardiac septation

40. EMBRYOLOGY : CVS
• End of 4th week, sickle shaped crest grows from roof of atrium : Septum
Primum
• Opening between septum primum & endocardial cushion: ostium primum
CVS Embryology
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41. EMBRYOLOGY : CVS
• Limbs of septum extend in direction of endocardial cushions
CVS Embryology
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42. EMBRYOLOGY : CVS
• Crescent shaped fold : septum secundum
• Never forms complete partition in atrial cavity
• Free concave edge overlaps ostium secundum
CVS Embryology
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43. EMBRYOLOGY : CVS
• Opening left by septum secundum : Oval foramen
CVS Embryology
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44. EMBRYOLOGY : CVS
•
Before birth foramen ovale allows blood to pass from right atrium into left atrium; reflux is
prevented by the valve. After birth foramen ovale normally closes by fusion of septum primum &
septum secundum.
CVS Embryology
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45. EMBRYOLOGY : CVS
CVS Embryology
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46. EMBRYOLOGY : CVS
•
During week 5, bulbus cordis & truncus arteriosus become divided by an aorticopulmonary
septum into pulmonary trunk & aorta.

47. EMBRYOLOGY : CVS
•
During week 5, bulbus cordis & truncus arteriosus become divided by an aorticopulmonary
septum into pulmonary trunk & aorta.

48. EMBRYOLOGY : CVS
•
Ventricles become partitioned by a crescentic fold which is open cranially until end of week 7.
CVS Embryology
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49. EMBRYOLOGY : CVS
• Primitive ventricle : give rise to most of left ventricle
CVS Embryology
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50. EMBRYOLOGY : CVS
• Bulbus cordis : forms most of right ventricle
CVS Embryology
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