Development of heart ,,embryology,,virbhan

1. CARDIAC EMBRYOLOGY &
FETAL CIRCULATION
Presenter Dr Virbhan Balai
Moderator- Dr Y.K Arora

2. The heart is mesodermal in origin.
Its formed from splanchnopleuric mesoderm.
The mesoderm constitute the cardiogenic area
Its closely related to pericardial cavity (derived
from intraembroyonic coelom).

3. Establishment of
the heart fields
BMP2 & 4 in mesoderm
WNT inhibition (from
“Anterior” Visceral
Endoderm) in anterior
mesoderm
BMP2,4+/Wnt- expression
pattern specifies cardiac
tissue (evidenced by
expression of NKX-2.5,
aka tinman)

4. Retinoic acid (RA) and other
factors determine the cranio-
caudal axis of heart primordia
• Primary heart field: left ventricle
• Posterior segment of primary heart
field: atria
• Secondary heart field: right ventricle
& outflow tract
• EXOGENOUS RETINOIDS CAN
INTERFERE WITH THIS PROCESS!
Carlson fig 17-17

5. Embryonic disc-relation ship of
pericardial cavity to other structure

6. Embryonic disc showing neural plate
and related structures

7. Formation of heart tube

8. Relation ship of heart tube
to pericardial cavity;
A. Before formation of head
fold.
B. After formation of head
fold.
C. C & D shows the process
of invagination of the
pericardial cavity by
single heart tube.

9. Repositioning the cardiogenic field
(mammals)

10. The heart is first seen in the form of right and
left endothelial heart tubes.
Soon fuse with each other
Single tube thus formed shows a series of
dilation.
Bulbus cordis
Ventricle
Atrium
Sinus venosus

12. Fusing cardiac primordia
“conotruncus”
(outflow tract)
future
ventricles
future
atria
septum transversum
(liver & diaphragm primordium)
21 days 22 days

13. Bulbus cordis is divisible into three parts-
Proximal one third is dilated- no sp name
Middle one third-CONUS
Distal one third-TRUNCUS ARTERIOSUS

14. Arterial & venous end of heart tube

15. Fate of various parts of heart tube

16. Prior to the completion of looping, heart shows primitive chambers (bulbous
cordis, ventricles and atria, and sinus venosus) and the regions of
separation between them (atrioventricular and bulboventricular sulcus).
Human Age: 25 days View
Atrioventricular
sulcus
Bulboventricular
sulcus

17. The truncus arteriosus
carries blood out of the
heart into the aortic sac
and subsequently into
the aortic arch vessels.
The conus cordis is a
major contributor to
the right ventricle

18. Folding and rotation of heart tube
• Ventricle moves ventrally
and to right
• Atrium moves dorsally
and to left
bulbus cordis
truncus arteriosus
aortic roots
ventricle
atrium
sinus venosus
22 days 23 days 24 days Langman’s fig 12-6

19. Heart tube-loops to right side
Cephalic portion bends
Ventral
Caudal
Right
Bulboventricular sulcus
Proximal tube expands-
Primitive ventricles
Distal(smaller)
Bulbus cordis

23. Formation of atria
The sinus venosus and primitive atrial
chamber are at first connected by a wide
opening.
Gradually the opening become narrows & shift
to right.
Finally it becomes a narrow slit.
The slit has right and left margin called right
and left venous valve.

24. Cranially these structure fuse to form a
structure called septum spurium.
The A-V canal divide into right and left halves
Two thickening, A-V cushion appear on its
dorsal and ventral walls.
They grow toward each other and fuse
The fused cushion forms septum
intermedium

25. Changes in sinu-atrial orifice

26. A.V canal division into right & left

27. Formation of interatrial septum
The atrial chamber undergoes division into
right and left halves by formation of two
septae which later fuse.
The septum primum- arise from the roof of
right atrium-grows towards AV canal
(ultimately fuse with septum intermedium)
The septum secundum- grows down from the
roof the atrial chamber, to the right of atrial
chamber.

29. Development of right atrium
Main part of RA is derived from the right half
of primitive atrium
The sinus venosus is absorbed into the RA by
great enlargment of sinuatrial orifice
Right half of AV canal is also absorbed into
RA
Left horn of sinus venosus remain very small.
It become part of the coronary sinus

30. The right common cardinal vein becomes part of
SVC
The right vitelline vein forms the terminal parts of
IVC
The right margin of the the original sinuatrial
orifice (i.e rt venous valve) expands greately and
divide into three parts-
Crista terminalis
Valve of IVC
Valve of cornary sinus

31. Incorporation of sinus venosus into RA

32. Fate of right & left venous valves-
The right venous valve expands greately and
forms crista terminalis, valve of IVC & the
valve of CS.
The left venous valve remain small and fuse
with IAS

33. Fate of right & left venous valves

34. Development of LA
The left atrium is derived from-
Left half of primitive atrial chamber
Left half of atrio-ventricular canal
Absorbed proximal parts of pulmonary veins

35. Absorption of pulmonary veins
Absorption of pulmonary veins into the LA
At first only one vein from the lungs enter the
atrium
The proximal part of vein is gradually
absorbed and is incorporated into the wall of
the atrium.
As a result of continued absorption of
tributeries, four vein (two right & two left)
finally open into atrium.

36. Absorption of pulmonary veins

37. Development of ventricle
Fate of bulbus cordis
Bulbus cordis is divisible into three parts
The proximal one third-merge with the cavity
of primitive right ventricle
The CONUS- forms the outflow tracts (smooth
parts) of both right and left ventricles.
Distal (TRUNCUS ARTERIOSUS)-

38. A spiral septum appears within the truncus
arteriosus and subdivides into the ascending
aorta and the pulmonary trunk.
It is formed by union of right superior and left
inferior truncus swellings or cushions.

39. Two parts of ventricular chamber
Part ‘1’ is derived from the proximla one third of bulbus cordis and
primitive ventricle, while part ‘2’ is from CONUS.

40. Formation of IVS
Interventricular septum grows upwards from
the floor of the bulbo-ventricular cavity and
divide the lower dilated part of this cavity into
right and left halves.
It meets the fused AV cushions (septum
intermedium) and partly fuse with them.
On the ext heart surface formation of IVS
correspond with bulbo-ventricular sulcus.

41. Two ridge, right and left bulbar ridges arise in the
wall of the bulbo-ventricular cavity(in the part der
from conus).
These ridges grow towards each other and fuse to
form bulbar septum.
The bulbar septum grows downward towards IVS
but doesnot quiet reach it.
The gap b/w upper edge of IVS & lower edge of
BS is filled by proliferation of tissue from AV
cushions.

44. Formation of AV valves
Dependent on AV cushions and ventricular myocardium…
Moore & Persaud fig 13-19

45. Exterior of the heart
A. Heart tube suspended by mesocardium
B. Appearance of hole in mesocardium
C. Disappearance of mesocardium resulting in
formation of transverse sinus of pericardium
D. B to D gradual freeing of heart tube from
septum transversum and folding of heart tube

48. Stages in the establishment of ext.
form of heart

49. Retrogression of left horn of sinus
venosus

50. THE ARTERIES
The greater part of first and second arch
arteries disappear.
In adult life first arch artery is represented by
the maxillary artery.
The second arch artery persist for some part of
fetal life as the stapedial artery; it contribute to
formation of ECA.

51. Fifth arch artery also disappears
The aortic sac is therefore connected only to
third, fourth and sixth arches.
The portion off the dorsal aorta b/w the
attachment of third and fourth arch arteries
(DUCTUS CAROTICUS), disappears on both
sides.

52. Relation of first aortic arch to heart tube
before and after fusion of heart tube

53. ventral view of heart
(35 days),Note the
aortic arches arising
from aortic sac and
terminate in the dorsal
aortae.

55. Fate of aortic archs-disappearance of
1st,2nd and 5th arches

56. Disappearance of ductus caroticus, part of
rt dorsal aorta and part of rt 6th arch

57. Changes in the aortic arch pattern (AS,1,2,3,5)
5th arch fails to form
2nd arch mostly disappears
• stapedial a.
• (hyoid a.?)
3rd arch:
• common carotid a.
• part of internal carotid a.
• internal and external
carotid aa. sprout from 3rd arch
Aortic Sac (AS):
• proximal part of aortic arch
• brachiocephalic a.
1st arch mostly disappears
• maxillary a.
• (part of external carotid a.?)
Aortic sac

58. Changes in the aortic arch pattern (4)
4th arch on left:
– arch of aorta
(from left common carotid a.
to left subclavian a. only)
4th arch on right:
– proximal segment of right
subclavian a. (rest of subclavian
a. from 7th intersegmental a. and
R dorsal aorta)

59. Changes in the aortic arch pattern (6)
(6th arch = pulmonary arch)
6th arch on left:
– left pulmonary artery
– distal segment persists as ductus arteriosus
6th arch on right:
– right pulmonary artery
– distal segment regresses

60. Aortic Arch
Anomalies
(A) Double aortic arch
abnormal persistence of right
distal segment
~1:1000 incidence –often assoc.
with dysphagia and/or dyspnea
(B) Right aortic arch
abnormal persistence of right
distal segment & regression of left
distal segment
~1:1000 incidence –usually
asymptomatic
(C) Aberrant right subclavian
(from aortic arch)
(abnormal regression of right
proximal segment & persistence of
right distal segment)
~1:100 incidence –often assoc.
with dysphagia and/or dyspnea;
also, R radial pulse may be weak
normally
regresses
normally
persists
normally
persists
Carlson fig 17-42

61. Adult derivatives of truncus
arteriosus,aortic sac and aortic arch

62. FETAL CIRCULATION
The circulation of fetus is essentially same as
in the adult except-
The source of oxygenated blood is not lungs
but placenta
Oxygenated blood from placenta comes to
fetus through umbilical vein
Oxygen reach blood reaching the RA through
IVC is directed through foramen ovale

63. Circulation
in the
human
adult

64. Fetal circulation

65. Changes in circulation at birth
Umbilical arteries occlude
Umbilical veins and ductus venosus occlude
Ductus arteriosus is occluded
The pulmonary vessel increase in size
Foramen ovale closes: LA pressure> RA pr.

66. The vessel that are occluded soon after birth
are, in due course, replaced by fibrous tissue,
and form the following ligamnets:
Vessel Remnant
Umbilical arteries Medial umbilical ligaments
Left umbilical vein Ligamentum teres of the liver
Ductus venosus Ligamentum venosum
Ductus arteriosus Ligamentum arteriosum

67. Time table-