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
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 tubes1 tubeprimitive heart
② arteries
③ veins
20d
cardiac tubes
End of 4w
Primitive heart
4w
8. 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
20d 4w End of 4w
Dorsal A Dorsal A Dorsal aortaAortic arches
Umbilical AVitelline A
9. 1 pair of anterior cardinal V
1 pair of posterior cardinal V
1 pair of vitelline V
1 pair of umbilical V
20d 4w End of 4w
Anterior
cardinal V
Posterior
cardinal V Umbilical VVitelline V Common cardinal V
Common
cardinal V
① cardiac tube
② arteries
③ veins
13. A. A cavity appears in the cardiogenic area
--pericardial cavity
B. Ventral of the cavity is cardiaogenic cords
--cardiaogenic plate
Pericardial cavity
cardiaogenic plate
18~19th day
14. C. cardiaogenic plate becomes hollow --cardiac tube
Pericardial cavity
cardiac tube
20th day
15. D. Cephalic folding:
Pericardial cavity: dorsal → ventral
Cardiac tube: ventral → dorsal
Pericardial
cavity
cardiac tube
22nd day
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, which connects both sides of the
pericardial cavity.
Cephalic end Arteries，Caudal end Veins
Pericardial
cavity
cardiac tube
Cephalic end Caudal end
Transverse sinus
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
21. Form a ‘U’ like structure, the cardiac loop--
bulboventricular loop.
The 24th d
sinus venosus
truncus
arteriosus
22. The 35th d
atrium
Aortic
arches
ventricle
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
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
Partitioning of atrioventricular canal
Partitioning of the primitive atrium
Partitioning of the primitive ventricle
Division of truncus arteriosus and bulbus
cordis
(from 27th day to 37th day)
25. Partitioning of atrioventricular canal
• Endocardiac cushion:
• The endocardial cushions grow toward each other and fuse
28. Foramen
primum
Septum
primum
Endocardiac
cushion
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
End of the 4th w
30. • 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.
End of the 5th w
Septum
primum
Foramen
secundum
Septum
secundum
31. Early 6th w
• 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.
Foramen
ovale
Septum
secundum
Foramen
secundum
Septum
primum
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. The 4th w
EC
• The muscular
Interventricular
septum grows
up from the floor
of the ventricle.
RV
LV
Inter-
ventricular
septum
Partitioning of the primitive ventricle
34. • Interventricular foramen
the muscular interven-
tricular septum keeps
growing toward endo-
cardial cushions, but left
an opening, called inter-
ventricular foramen.
End of the 5th w
EC
Inter-
ventricular
foramen
IV
septum
35. • Membranous interventricular septum:
Derived from right bulbar ridge, left bulbar ridge and the
endocardial cushion,closes the interventricular foramen
endocardial
cushions
Membranous
interventricular
septum
End of the 7th w
37. The 5th w
Bulbus
cordis
Truncus
arteriosus
Truncal ridge
Bulbar ridge
• Two spiral truncal ridges/ bulbar ridges grow from the
inner walls of the truncus arteriosus and bulbus cordis.
Division of truncus arteriosus and bulbus cordis
38. • These ridges twist around each other and fuse to
form a spiral aorticopulmonary septum.
Pulmonary
artery Aortico-
pulmonary
septum
Aorta
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.
44. 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
Circulatory changes after birth
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
A. Perforation of valve of
ovale foramen
B. Excessive resorption of the
septum primum
C.Inadequate development of
the septum secundum.
D.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. 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.
Patent ductus arteriosus
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
A complex of 4 defects:
Pulmonary stenosis
Overriding aorta
Ventricular septal defect
Hypertrophy of the right
ventricle
Unequal division of the truncus and bulbus
53. 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 ）
Key points
