The document provides an overview of heart development from the 3rd week of gestation. It discusses the formation of the primary and secondary heart fields, cardiac looping, septation of the atria, ventricles and great arteries. Key events include initiation of heartbeat in the 4th week, completion of development by the 7th week, and the crucial period of anomalies from 3-6 weeks. Molecular regulation and left-sided patterning are also covered.

1. DEVELOPMENT OF HEART- OVERVIEW
DR.D.SURESH
FIRST YEAR CARDIOLOGY RESIDENT

2. INTRODUCTION
• Cardiovascular system starts to develop by middle of 3rd week of
intrauterine life.
• Heart starts to beat by early 4th week (23 rd day).
• Entire process of heart development completes by 7th week.
• Crucial period for development of anomalies is 3 - 6 weeks.

3. PRIMARY HEART FIELDS
• Progenitor heart cells lie in
the epiblast, from they
migrate to splanchnic
mesoderm, which forms
primary heart fields.
• PHF
1. Atrium
2.Left ventricle
3. Parts of right ventricle.
.

4. SECONDARY HEART FIELDS
• Secondary heart fields(SHF)
develop in the splanchnic
mesoderm ventral to pharynx.
• SHF
1. Parts of Right ventricle
2. outflow tract ( conus cordis
and truncus arteriosus)
• SHF - Laterality of heart which
occurs on day 16

5. Molecular regulation- HEART FIELDS
• Induction of heart by NKX 2.5.
• BMP 2 & 4 Secreted by
endoderm and lateral plate
mesoderm.
• WNT INHIBITION by CRESCENT
and CEREBRUS -.
• RETINOIC ACID(RA) – contribute
to the venous portion of heart
tube.

6. LEFT SIDEDNESS
5 - HT - transcription factor
PITX2.
PITX2 - master gene for left
sidedness.
Laterality defects such as
dextrocardia, VSD, ASD, DORV,
OUTFLOW Defects occurs.
Tertogenicity of SSRI explains the
importance of 5 –HT Signaling
pathway.

7. Heart tube formation
• PHF are induced by the
endoderm to form cardiac
myoblasts and blood islands.
• Blood islands will forms blood
cells and vessels by
vasculogenesis.
• Blood islands unite and forms a
horseshoe shaped endothelial
tube , cardiogenic region.
• Pericardial cavity develops over
it

8. Formation and position of heart tube
• Cardiogenic area lie anterior to
oropharyngeal membrane.
• Growth of the brain and cephalic
folding of embryo pulls the
oropharyngeal membrane
cranialy ,while heart and
pericardial cavity moved first to
cervical region and then to
thorax.
• .

9. • As a embryo grows and bends
cephalocaudally, caudal regions
of the paired cardiac tube
merges except at the
caudalmost parts
• Central parts of the heart tube
expands to form the outflow
tract and ventricular regions

10. • Now the heart becomes a
continuous tube with an inner
endothelium and an outer
myocardial lining.
• Heart tube remains attached to
dorsal side of pericardium by the
dorsal messocardium.
• Middle section of dorsal
mesocardium disappears and
forms transverse pericardial sinus
which connects both sides of the
pericardial cavity.
• Myocardium thickens and secrete a
layer of ECM called cardiac jelly .

11. • Heart tube consists of three
layer
1.Endocardium – internal
endothelial lining of heart.
2. Myocardium – muscular wall
3. Epicardium – visceral
myocardium, formation of
coronary arteries

12. Cardiac looping
• Heart tube continues to elongate
as cells are added from SHF to its
cranial end.
• Lengthening process is essential
for normal formation of part of
right ventricle and outflow tract
region and looping process.

13. • Cardiac tube begins to bend on
day 23 and completes on day 28
• Cephalic portion of the tube
bends ventrally, caudally and to
the right.
• Caudal (atrial) portion shifts
dorsocranially and to the left.

14. Cardiac looping
• Conotruncal portion of heart tube
moves from the right side of
pericardium to the more medial
position,results from the formation
of two transverse dilations of
atrium.
• Trabeculae occurs in the primitive
ventricle becomes left ventricle.
• Bulboventricular sulcus – junction
between the ventricle and bulbus
cordis. Its called the primary
interventricular foramen.

15. Bulbus cordis
Proximal parts :
• Trabeculated parts of the right
ventricle
• Conus cordis :
Outflow tracts of both ventricle.
• Truncus arteriosus –
• Roots and proximal portion of aorta
and pulmonary artery.

16. Sinus venosus development
Each horns receives
• 1. viteline veins
• 2.. Umblical veins
• 3. common cardinal veins.
• During 4th and 5th week shifting
occurs predominantly to right -
obliteration of left vitelline veins
at 5th week and obliteration of
left common cardinal veins at
10th weeks

17. Cont..
• Only oblique vein of left atrium
and coronary sinus persists.
• Right sinus horns - smooth
walled part of right atrium.
• Sinus venosus also gives rise to
the visceral pericardium of the
heart.
• Some of sinus venosus cells
infiltrate into the heart and forms
the conducting system of the
heart.

18. • Its entrance sinuatrial orifice
flanked on each side by rt and lt
venous valves.
• Dorsocranially valves fuses and
forms a sputum spurium.
• Lt venous valve and sputum
spurium helps in the development
of atrial septum
• Rt venous valve develops into
• 1.valve of IVC
• 2. valve of coronary sinus

19. Abnormalities of cardiac looping
• Dextrocardia : the location of the heart in the right hemithorax with
the base to apex axis to the right
• Mesocardia : cardiac base to apex axis directed to the midline of the
thorax or with ventricular apices equally directed to both right and
left sides

20. Cardiac septa formation
1.Endocardial cushions-
septum formation by two
actively growing ridges
2. septum formation by single
actively growing cell mass,
such as septum primum and
septum secundum.
3.IVS - septum formation by
merging two expanding
portions of the walls of heart.

21. Formation of interatrial septum
• Septum primum –
• End of 4th week
• Sickle shaped crest grows from
the roof of common atrium
towards endocardial cushions.
• Opening between the lower rim
of septum primum and
endocardial cushions – ostium
primum.

22. Cont..
• Superior and inferior
endocardial cushions grows
along the edge of septum
primum and closes the ostium
primum.
• Before closure , cell death occurs
in the upper portion of septum
primum and forms the ostium
secundum

23. • New crescent shaped fold called
septum secundum appears .
• Left venous valve and septum
spurium fuse with the right side
of the septum secundum .
• It overlap the ostium secundum
• The opening left by ostium
secundum is called oval foramen
(foramen ovale)
• Remaining parts of septum
primum becomes the valve of
the oval foramen.

24. Formation of left atrium and pulmonary veins
Dorsal mesenchymal
protrusion(DMP) - the
proliferating mesenchyme of
the dorsal mesocardium.
This tissues grows with the
septum primum towards the
atriventricular canal.

25. • Pulmonary veins is positioned.
• Remaining parts of DMP
contributes to endocardial
cushion formation.
Clinical correlates:
TAPVR

26. AV CANAL SEPTUM FORMATION
• FOUR endocardial cushions
appears at the end of 4 weeks.
• AV CANAL access only to
primitive left ventricle and is
separated by bulbo ventricular
flange.
• At the end of fifth
week,posterior extremity of
flange terminates midway along
the base of dorsal endocardial
cushions.

27. • AV canal enlarges to right -
direct access to rt and lt
ventricle.
• Two lateral endocardial cushions
appear on the right and left
borders of canal.results into rt
and left av valves
• Each AV Orifices is surrounded
by local proliferations of
mesenchymal tissues
• Blood flows hollows out,
mesenchymal tissue becomes
fibrous and forms the AV
VALVES.

28. • AV valves remain attached to the ventricular wall by the muscular
cords.
• Muscular cords degenerates and is replaced by dense connective
tissues to become chordae tendinae.
• AV Valves are connected to the papillary muscles by means of
chordae tendinae.

29. Septum formation in the truncus arteriosus
and conus cordis
• Right superior truncus swelling
grow distally and to the left and
on
the left inferior truncus grow
distally and on the right.
• Swelling twisted around each
other and forms the
aorticopulmonary septum
divides the truncus into an aortic
and pulmonary channel.

30. Cont..
• Similar swellings appear on the
dorsal and ventral walls of conus
cordis ,grows towards each
other and distally to unite with
the truncus septum.
• Septum divides the conus into
an anterolateral portion
(outflow tract of RV) AND
POSTEROMEDIAL
portion(outflow tract of LV)

31. INTERVENTRICLUAR SEPTUM- MUSCULAR
PART
• By the end of 4TH week ,two
primitive ventricles begin to
expand.
• Medial walls of the expanding
ventricles become apposed and
gradually merge – muscular
ventricular septum.

32. • Interventricular foramen – space
between the free rim of muscular
ventricular septum and fused
endocardial cushions.
• Interventricular foramen closes by
completion of conus septum and
outgrowth of tissue from the
anterior endocardial cushions
along the top of muscular
interventricular septum.

33. BULBAR PARTS
• Right and left bulbar ridges arise
in bulboventricular cavity
• These ridges grows towards each
other to form bulbar septum
• Grows downwards towards
muscular part of IVS but does
not reach it

34. MEMBRANOUS PARTS
• Proliferation of tissue from
inferior A-V endocardial
cushions fills the gap between
muscular and bulbar parts of IVS
• TWO parts :
• INTERVENTRIULCAR
• ATRIOVENTRICULAR – separates LV
& RA

35. Semilunar valves
• Semilunar valves visible as small tubercles found on the main truncus
swellings.
• Third tubercle appear in both channels opposite the fused truncus
swellings.
• Tubercles hollow out at their upper surface forming semilunar valves.
• Neural crest cells contribute to the formation of semilunar valves.

36. Aortic Arch
• Each pharyngeal arch has own
cranial nerve and arteries.
• Aortic arches arise from the aortic
sac ,the most distal part of truncus
arteriosus.
• .
• By day 27,most parts of 1st and 2nd
arch disappears.
• First arch artery is represented by
maxillary artery.
• Second arch artery is represented
by stapedial artery.

37. • 3rd arch
• Common carotid artery
• Part of internal carotid artery
• External carotid atery arises as
sprout from 3rd arch
5th arch fails to form

38. FOURTH ARCH
4th arch on right
• Proximal segment of
subclavian artery
• Distal segment - 7th
intersegmental and Rt dorsal
aorta.
4th arch on left
Arch of aorta

39. • 6th arch on right
• Right pulmonary artery
• Distal segment regress
6th arch on left
• Left pulmonary artery
• Distal segment as ductus
arteriosus
• .

40. Venous system
Inferior vena cava
• Rt Vitelline veins –
hepatocardiac portion of ivc
• Rt subcardinal veins – renal
segment of ivc
• Rt sacrocardinal veins.
Superior venae cava
ANASTOMOSIS of rt common
cardinal veins and proximal
portion of right anterior cardinal
veins.

41. Conducting system of heart
• Pacemaker for the heart lies in the caudal part of the left cardiac
tube.
• AFTER cardiac looping ,sinus venosus assumes this function’
• Pacemaker lies near the opening of svc into the right atrium ,thus
sinoatrial node is formed.

42. • Av node and bundle of his are derived from two sources:
1.myocardial cells in the left wall of sinus venosus.
2.myocardial cells from AV Canal.

43. NEURAL CREST CELLS
• Cardiac neural crest cells - the
formation endocardial formation in
both conus and truncus arteriosus.
• Neural crest cells - the smooth
muscle and connective tissues of
the arch vessels.
• Heart defects caused by this
mechanism include TOF,PS,PTA
AND TGA.

45. THANK YOU