1. the Cardiovascular System
Development of
the Cardiovascular System

2. Contents Establishment of the primordial cardio-vascular system
Development of the heart
Blood circulation of fetus and circulatory changes after birth
Congenital defects of the cardiovascular system

3. Establishment of the Primordial Cardiovascular System

4. Yolk sac
mesenchyme cells
blood islands
Central C Peripheral C
Primitive Blood cell Endothelial C
Blood C Endothelial
tubule
Endothelial tube meshwork

5. Endothelial tube network appears in chorion and body stalk, and connect to vitelline circulation.
By the 18-20th days, endothelial tube network appears in intraembry-onic mesenchyma to form intraembryonic endothe-lial tube network.

6. By the end of 3rd week, intraembryonic and extra-embryonic endothelial tube networks connect to each other.
Endothelial tube networks fuse or disappear to form primordial cardiovas-cular system.

7. ① cardiac tube:2 tubes1 tubeprimitive heart ② arteries ③ veins
cardiac tubes
20d 4w
End of 4w
① cardiac tube:2 tubes1 tubeprimitive heart
② arteries
③ veins

8. ① cardiac tube ② arteries ③ veins 2 dorsal A  1 ,many branches
Aortic arches
Dorsal aorta
20d 4w
End of 4w
Vitelline A
Umbilical A
① cardiac tube
② arteries
③ veins
2 dorsal A  1 ,many branches
Few pairs of vitelline A
1 pair of umbilical A
6 pairs of aortic arches

9. ① cardiac tube ② arteries ③ veins 1 pair of anterior cardinal V
Posterior cardinal V
Vitelline V
Common cardinal V
Umbilical V
20d 4w
End of 4w
① cardiac tube
② arteries
③ veins
1 pair of anterior cardinal V
1 pair of posterior cardinal V
1 pair of vitelline V
1 pair of umbilical V
Common
cardinal V

10. vitelline, umbilical and embryonic circulation.

11. Development of the Heart
Development of the cardiac tube
Morphogenesis of the heart
Partitioning of heart chambers

12. Development of the cardiac tube
Cardiogenic area
Oropharyngeal membrane
Cardiogenic area is anterior to
the oropharyngeal membrane.

13. A cavity appears in the cardiogenic area --pericardial cavity
cardiaogenic plate
18~19th day
A cavity appears in the cardiogenic area
--pericardial cavity
B. Ventral of the cavity is cardiaogenic cords
--cardiaogenic plate

14. C. cardiaogenic plate becomes hollow --cardiac tube
Pericardial cavity
cardiac tube
20th day
C. cardiaogenic plate becomes hollow --cardiac tube

15. Pericardial cavity: dorsal → ventral Cardiac tube: ventral → dorsal
22nd day
D. Cephalic folding:
Pericardial cavity: dorsal → ventral
Cardiac tube: ventral → dorsal

16. E. Lateral folding: 2 cardiac tubes → single cardiac tube.
F. The tube remains attached to the dorsal side of the
pericardial cavity by the dorsal mesocardium.

17. G. The dorsal mesocardium breaks down to form the
Transverse sinus
Pericardial cavity
cardiac tube
Cephalic end
Caudal end
G. The dorsal mesocardium breaks down to form the
transverse sinus, which connects both sides of the
pericardial cavity.
Cephalic end  Arteries，Caudal end  Veins

18. Morphogenesis of the heart
Vein end
Cardiac tube
Artery end
The 21st d
Part of the cardiac tubes merged
Cephalic end  A
Caudal end  V

19. Cardiac tubes almost merged
atrium
ventricle
bulbus cordis
Cardiac tubes almost merged
Three expansions
Bulbus cordis
Ventricle
Atrium
The 22nd d

20. The 4th expansion, the sinus venosus appears
The truncus arteriosus appears
The bulbus cordis and ventricle grow faster than other regions, the cardiac tube starts to bend.
The 23rd d
atrium
bulbus
cordis
truncus
arteriosus
sinus
venosus
ventricle
bulboventricular portion of heart tube grows rapidly, bends forming a loop

21. Form a ‘U’ like structure, the cardiac loop--bulboventricular loop.
The 24th d
sinus venosus
truncus
arteriosus
Form a ‘U’ like structure, the cardiac loop--bulboventricular loop.

22. The bulboventricular loop continues to grow and bend:
Atrium shifts in dorso-cranial direction and bulges laterally on each side of bulbus.
Sinus venousus located at caudal portion of atrium
The 35th d
atrium
Aortic
arches
ventricle

23. Primary ventricle develop into the left ventricle.
The bulbus cordis proximal portion develops into the right ventricle.
Atrioventricular canal: atrioventricular junction remains narrow.
The 35th d
atrium
Aortic
arches
ventricle
The normal heart shape was established, but partitioning has not completed.

24. Partitioning of Heart Chambers
(from 27th day to 37th day)
Partitioning of atrioventricular canal
Partitioning of the primitive atrium
Partitioning of the primitive ventricle
Division of truncus arteriosus and bulbus cordis

25. Partitioning of atrioventricular canal
Endocardiac cushion:
The endocardial cushions grow toward each other and fuse

27. Lateral atrioventricular cushion: form atrioventricular
valve. Left → bicuspid, right → tricuspid
Bicuspid
Ttricuspid
Endocardiac
cushion

28. Partitioning of the primitive atrium
Septum primum: a thin sickle-shaped crest appearing from dorso-cranial wall of atrium.
Foramen primum: septum primum grows toward the endocardial cushions, leaving an opening between its lower edge and the endocardial cushions
Foramen
primum
Septum
Endocardiac
cushion
End of the 4th w

29. Early 5th w
Small holes
Foramen primum

30. End of the 5th w
Septum
primum
Foramen
secundum
Foramen secundum Small holes fuse to form the foramen se-cundum,The foramen primum closed.
Septum secundum： another membrane appears on the right of the septum primum.

31. The septum primum covers the foramen ovale, serves as a valve.
secundum
primum
Foramen ovale : septum secundum extends downward to cover the foramen secundum, but leaving an opening.
The septum primum covers the foramen ovale, serves as a valve.
Early 6th w

32. Before birth, blood can flow from right atrium toward the left atrium
After birth, two septums fuse , the foramen ovale closed complete, and atrium is separated into R and L atria.

33. Partitioning of the primitive ventricle
The muscular Interventricular septum grows up from the floor of the ventricle. EC LV RV
Inter-ventricular septum
The 4th w

34. Interventricular foramen the muscular interven- tricular septum keeps
growing toward endo-
cardial cushions, but left
an opening, called inter-
ventricular foramen. EC
Inter-
ventricular
foramen
IV septum
End of the 5th w

35. Membranous interventricular septum:
Derived from right bulbar ridge, left bulbar ridge and the endocardial cushion,closes the interventricular foramen
Membranous interventricular septum
endocardial cushions
End of the 7th w

36. Left ventricle Pulmonary artery Right ventricle Aorta
The interventricular septum:
muscular partion + membranous portion
Left ventricle Pulmonary artery
Right ventricle Aorta

37. Division of truncus arteriosus and bulbus cordis
Truncal ridge
Bulbar ridge
The 5th w
Two spiral truncal ridges/ bulbar ridges grow from the inner walls of the truncus arteriosus and bulbus cordis.

38. Pulmonary
artery
Aortico-
pulmonary
septum
Aorta
These ridges twist around each other and fuse to form a spiral aorticopulmonary septum.

39. The ridges spiral neatly down the truncus until they reach the ventricles.

40. As the same time, the division of the ventricle is completed.
Aorticopulmonary septum divides truncus arteriosus and bulbus cordis into two channels: pulmonary trunk connecting to the right ventricle; aorta connecting to the left ventricle.

41. Blood circulation of fetus and circulatory changes after birth

42. Before birth
Placental circulation: umbilical A. & V.

43. Blood circulation of fetus

44. Circulatory changes after birth
a.Umbilical A: distal parts becomes into medial umbilical ligament, but proximal portions persist as superior vesical arteries.
b. Umbilical V and ducts venousus: constrict and becomes into ligamen-tum teres hepatis and ligamentum venosus
c. Ductus arteriosus: constrict and become ligamentum arteriosum
d. Foramen ovale closed

45. Congenital defects of the cardiovascular system

46. Atrial septal defect
An atrial septal defect (ASD) is a common congenital heart anomaly.
The most common form of ASD is patent oval foramen.
Consequently there is a mixing of oxygenated and deoxygenated blood.

47. Atrial septal defect Perforation of valve of ovale foramen
Excessive resorption of the septum primum
Inadequate development of the septum secundum.
B+C
Endocardial cushion defect with septum primum defect

48. Ventricular septal defect
Muscular part of the ventricular septum: sparsely
Membranous part of the ventricular septum defect:commonly
Unfused endocardial cushion,bulbar ridge and muscular septum or over absorption of membranous septum

49. Patent ductus arteriosus
Ductus arteriosus fails to be closed after birth.
Isolated or combined with other defects.
Blood will be shunted from the aorta to the lungs,
eventually causing irreversible pulmonary hypertension.

50. Persistent truncus arteriosus
Aorticopulmonary septal
ridges fail to fuse and descend;
Truncus overrides both
ventricles;
Accompanied by ventricular
septal defect;
Resulting in cyanotic defect.

51. Transposition of great vessels
Aorticopulmonary septum failing to follow its spiral course and descending straight downward
Aorta originates from right ventricle, pulmonary artery from left
Usually combined with patent ductus arteriosus

52. Tetralogy of Fallot Unequal division of the truncus and bulbus
A complex of 4 defects:
Pulmonary stenosis
Overriding aorta
Ventricular septal defect
Hypertrophy of the right ventricle

53. Key points Morphogenesis of the heart
Partitioning of atrioventricular canal, autrium, ventricle, and truncus arteriosus and bulbus cordis
Congenital defects of the cardiovascular system（ Tetralogy of Fallot ）

54. Prepare for Development of Urogenital System