Heart Development made easy

1. DEVELOPMENT OF THE HEART
By: Gan Quan Fu

2. CONTENT
1. Introduction
2. Fusion of Heart Tube
3. The Bulbus Cordis
4. The Sinus venosus
5. Formation of Atria
6. Separation of Aorta & Pulmonary
Trunk)
7. The Ventricles
8. The Exterior of Heart
9. Development of Heart Valve
10. Development of the Heart
conducting system
11. Timeline
12. Congenital Anomalies of Heart
By: Gan Quan Fu

3. By: Gan Quan Fu

4. INTRODUCTION
Mesodermal origin
Formed from angioblastic tissues that arise from
Splanchnopleuric Mesoderm (Cardiogenic area).
After formation of the head fold, this tube lies dorsal
to pericardial cavity & ventral to foregut.
Tube invaginates pericardial sac from dorsal side,
splanchnopleuric mesoderm lining the dorsal side of
pericardial cavity proliferates to form a thick layer
(myoepicardial mantle).
When invagination complete, myoepicardial mantle
completely surrounds the heart tube and give rise to
myocardium and also the epicardium.
Parietal layer of pericardium is derived from
somatopleuric mesoderm.
By: Gan Quan Fu

5. By: Gan Quan Fu

6. HEART TUBE
1st seen in form of right and left
endothelial heart tube.
Fuse and form single tube.
(Cranial to Caudal)
The single tube shows series of
dilatation:
Bulbus Cordis
Primitive Ventricle
Primitive Atrium
Sinus Venosus
Primitive Ventricle and Atrium
connected by a narrow
atrioventricular canal/
atrioventricular sulcus.
By: Gan Quan Fu

7. BULBUS CORDIS
Lies at arterial end of heart
Divisible into:
Proximal Part = Conus
Distal Part = Truncus
arteriosus
Truncus arteriosus
continuous distally with
aortic sac.
Aortic Sac is continuous
distally with right and left
pharyngeal arch arteries.
Arteries arch backwards to
become continuous with
right and left dorsal aortae.
By: Gan Quan Fu

8. HEART TUBES IN RELATION TO RIGHT AND LEFT
DORSAL AORTA
By: Gan Quan Fu

9. SINUS VENOSUS
Lies at venous end of
heart
It has right and left horns
(prolongations of sinus
venosus)
Each Horns are joined by:
One vitelline vein (from the
yolk sac)
One umbilical vein (from
the placenta)
One common cardinal vein
(from the body wall)
By: Gan Quan Fu

10. By: Gan Quan Fu

11. FORMATION OF ATRIA (SINU-ATRIAL ORIFICE)
Sinus venosus and
primitive atrial chamber
are 1st connected by wide
opening.
Gradually opening
becomes narrow & shifts
to right.
Finally becomes a narrow
slit. (The slit has right &
left margins known as
right & left venous
valves).
Cranially these 2 valve
fuse to form septum
By: Gan Quan Fu

12. FORMATION OF ATRIA (ATRIOVENTRICULAR
CANAL)
2 thickenings
(atrioventricular
cushions) appear on
dorsal and ventral
walls.
Grow towards each
other and fuse to form
septum intermedium.
By: Gan Quan Fu

13. FORMATION OF ATRIA (INTERATRIAL SEPTUM)
Atrial chamber undergoes division into right and
left by formation of 2 septa.
1. Septum Primum
2. Septa Secundum
By: Gan Quan Fu

14. FORMATION OF ATRIA (SEPTUM PRIMUM)
Arises from roof of atrium
towards atrioventricular canal
and form foramen primum.
Before foramen primum close
(Septum primum fuse with
septum intermedium), a new
gap (foramen secundum) is
form on upper part of foramen
primum by breaking down of
upper part of septum primum.
Septum primum now has a
free upper edge.
This is to ensure
communication between left
and right atria.
By: Gan Quan Fu

15. FORMATION OF ATRIA (SEPTUM SECUNDUM)
Arises downwards from roof of atrial chamber at
the right of septum primum.
Overlap with free edge of septum primum and
form foramen ovale (valvular aperture that
allows blood to flow from right to left).
After birth, foramen ovale is obliterated by
fusion of septum primum and septum
secundum.
Annulus ovalis  Lower free edge of septum
secundum
Fossa Ovalis  Septum primum
By: Gan Quan Fu

16. DEVELOPMENT OF RIGHT ATRIUM
Sinus venosus is absorbed into right atrium by
great enlargement of sinu-artrial orifice.
Left horn  Part of coronary sinus
Right common cardinal  Part of superior vena cava
Right vitelline vein  Terminal part of inferior vena
cava
Right margin of original sinu-atrial orifice (right & left
venous valve) expands and divide into:
Crista terminalis
Valve of inferior vena cava
Valve of coronary sinus
Right half of atrioventricular canal is also
absorbed into right atrium.
By: Gan Quan Fu

17. DEVELOPMENT OF LEFT ATRIUM
During the beginning of
formation of septum
primum, single pulmonary
vein open into left half of
atrium.
This pulmonary vein divide
into left and right branches.
Gradually the parts of
pulmonary veins nearest to
left atrium are absorbed
into the atrium resulting in
4 separate veins (2 each
side).
By: Gan Quan Fu

18. SEPARATION OF AORTA AND PULMONARY
TRUNK
Spiral Septum appears
within truncus arteriosus
and subdivides it into
ascending aorta and
pulmonary arteries.
They fuse along the axis of
the cylinder extending down
towards the ventricles.
Interventricular foramen
obliterated by mass of
endocardial tissues from
interventricular septum,
endocardial cushions &
By: Gan Quan Fu

19. DEVELOPMENT OF VENTRICLES
(INTERVENTRICULAR SEPTUM)
Conus of bulbus cordis merge with
cavity of primitive ventricle.
Interventricular septum grows
upwards from the floor of bulbo-
ventricular cavity & divide it into right
& left halves.
2 ridges (right & Left bulbar ridges)
from the wall of the conical part of
bulbar cavity (Spiral septum), grows
towards each other and fuse form
bulbar septum.
The gap between upper edge of
interventricular septum and lower
edge of bulbar septum, is filled by
proliferation of tissues from
atrioventricular cushions.
By: Gan Quan Fu

20. EXTERIOR OF HEART
Heart tube is suspended from the dorsal wall of the
pericardial cavity by 2 layers of percardium which
constitude dorsal mesocardium.
Mesocardium disappears and heart tube lies within
the pericardial sac.
Caudal part of the heart tube (atrium, sinus venosus)
is embedded within the septum transversum
By: Gan Quan Fu

21. EXTERIOR OF HEART
Bulbus cordis and ventricle in pericardial cavity grows
rapidly & becomes folded to form U-shape Bulbo-
ventricular loop.
The atrium and sinus venosus freed from septum
transversum. (Lie behind and above the ventricle and
the heart tube is now S shaped)
Arterial and venous ends come closer to each other
and the space between them becomes the transverse
sinus of pericardium.
By: Gan Quan Fu

22. EXTERIOR OF THE HEART
Till now, bulbus cordis (conus) & ventricle are
separated by deep bulboventricular sulcus.
Sulcus gradually becomes narrow, bulbus
cordis & ventricle come to form 1 chamber
which communicates with truncus arteriosus.
The atrial chamber which lies behind the
upper part of ventricle expands and projects
forwards on either side of the truncus.
Finally heart assumes its definitive shape.
By: Gan Quan Fu

23. VALVES OF HEART (MITRAL & TRICUSPID)
Formed by proliferation of connective tissue
under endocardium of left and right atrio-
ventricular canals.
By: Gan Quan Fu

24. VALVES OF HEART (PULMONARY & AORTIC)
Derived from endocardial cushions formed at
junction of truncus arteriosus and the conus
which grows and fuse with each other.
With separation of aortic and pulmonary trunk
each cushions are subdivided into 2 parts (each
in each orifice).
2 more cushions (anterior and posterior) appear.
 3 cushions in each opening which the 3
cusps of the corresponding valve develops.
Pulmonary valve is initially ventral to aortic
valve,. Subsequently rotation happens and
pulmonary valve lie ventral to left aortic valve.
By: Gan Quan Fu

25. DEVELOPMENT OF CONDUCTING SYSTEM OF
HEART
When there are 2 heart tubes, a pacemaker
(which later forms sinu-atrial node) lies in caudal
part of left tube.
After fusion of 2 tubes it lies in sinus venosus.
Comes to lie near to opening of superior vena
cava when sinus venosus is incorporated into
right ventricle.
Atrio-ventricular node and atrio-ventricular
bundle form in left wall of sinus venosus and in
atrio-ventricular canal.
After sinus venosus is absorbed into right
atrium, atrio-ventricular node comes to lie near
the interatrial septum.
By: Gan Quan Fu

26. TIMELINE ON FORMATION OF HEART
Early 4th week
The pair of lateral endocardial tubes fuse
5th to 6th week
A pair of septa, Septum Primum & Septum Secundum
separates right & left atria
Development of bicuspid and tricuspid atrioventricular
valve
6th week
Muscular ventricular septum partially separates the
ventricles
7th & 8th week
Spiral septum separates ascending aorta & pulmonary
trunk
Swellings within truncus arteriosus give rise to semilunar
valves of aorta & pulmonary trunk
Complete ventricular septation
By: Gan Quan Fu

27. CONGENITAL ANOMALIES OF HEART
Anomalies of Position
Atresia or Stenosis
Abnormal Growth
Defective Formation of Septa
Anomalies of Relationship of Chambers to
Great Vessels
By: Gan Quan Fu

28. ANOMALIES OF POSITION
Dextrocardia
Chambers and blood vessels of heart are reversed
from side to side (i.e. all structures that normally lie
on right side are on left and vice versa)
Maybe a part of the condition called situs inversus
(Organs are transposed)
If not part of situs inversus, usually accompanied by
anomalies of heart chambers and great vessels.
Ectopia Cordis
Heart lies exposed, on front of the chest and can be
seen from outside, due to defective development of
chest wall.
By: Gan Quan Fu

29. ATRESIA OR STENOSIS
Too narrow opening (stenosis) or no opening
(atresia) of the orifices of heart.
Aortic and pulmonary passages may also show
supravalvular or subvalvular stenosis.
Alternately, the openings may be too large and
valves becomes incompetent.
In pulmonary stenosis  foramen ovale and
ductus arteriosus remain patent.
In aortic stenosis  ductus arteriosus is patent
and blood flows into aorta through it.
By: Gan Quan Fu

30. ABNORMAL GROWTH
There maybe acessory cusps in the valves
Congenital tumors may be formed
Left atrium may be partially subdivided by a
transverse septum.
Myocardium may be poorly developed
(hypoplasia).
By: Gan Quan Fu

31. DEFECTIVE FORMATION OF SEPTA
1. INTERATRIAL SEPTAL DEFECTS
Osteum Primum Defect (image A)
Septum primum fail to reach atrio-ventricular
endocardial cushions  Foramen primum persist.
Osteum Secundum Defect (image B)
Septum secundum fail to develop  foramen
secundum remains wide open.
Patent Foramen Ovale (image C)
Septum Primum and Secundum may develop
normally but the Oblique valvular passage between
them may remain patent.
By: Gan Quan Fu

32. DEFECTIVE FORMATION OF SEPTA
Interventricular Septal Defects (image D)
Maybe seen either in the membranous or muscular
part of the septum
Most common congenital anomalies of the heart.
Patent Truncus Arteriosus
Defects of the spiral septum
Spiral Septum may not be formed at all. Partial
absence of the septum leads to
communications(shunts)between the aorta and
pulmonary trunk.
Atrio-ventricular canal defect / Persistent atrio-
ventricular canal
Defective formation of AV cushions, 4 chambers of
heart may intercommunicate.
By: Gan Quan Fu

33. COMBINED DEFECTS
Tetralogy of Fallot
Interventricular septal Defect
Aorta overriding the free upper edge of
ventricular septum
Pulmonary Stenosis
Hypertrophy of the Right Ventricle
By: Gan Quan Fu

34. ANOMALIES OF RELATIONSHIP OF CHAMBERS
TO GREAT VESSELS
Transposition of Great Vessels
The aorta arises from the right ventricle and the
pulmonary trunk from the left ventricle.
Taussig-Bing Syndrome
The aorta arises from the right ventricle and
pulmonary trunk overrides both the right and left
ventricle.
Interventricular defect
The Superior Vena Cava may end in the Left
Atrium
Pulmonary Veins may end in the Right Atrium or
one of it’s tributaries.
By: Gan Quan Fu

35. SUMMARY
Heart primodium forms in a horseshoe-shape
region of splanchnopleuric mesoderm at cranial
end of germ disc (Cardiogenic Region).
In response to signals from underlying
endoderm, angioblastic cords in this region
coalesce to form a pair of lateral heart tube.
Early of 4th week, they fuse to form primitive
heart tube.
Between weeks 5 and 8, primitive heart tube
undergoes process of looping, remodelling, and
septation that transform it’s single lumen into 4
chambers, thus laying down the basis for
separation of pulmonary and systemic
circulation
By: Gan Quan Fu

36. REFERENCES
Larsen, W.J. (1997) Human Embryology, 2nd
edn. Hong Kong; Churchill Livingstone.
Singh, I. & Pal, G.P. (1976) Human
Embryology, 7th edn. India; Macmillan.
By: Gan Quan Fu

37. Q&A SESSION !!!!
By: Gan Quan Fu

38. By: Gan Quan Fu