The document summarizes the development of the heart tube from the early stages of gestation. It discusses how progenitor heart cells migrate to form the primary heart field, which induces the formation of the heart tube. The heart tube initially consists of endothelial, myocardial and epicardial layers. It then undergoes looping and fusion of the two tubes. The document further describes the formation of the atria, ventricles, and septa. In particular, it discusses the formation of the interatrial septum by septum primum, secundum and the foramen ovale, as well as the muscular and membranous parts of the interventricular septum. Some congenital heart defects are also summarized like atrial

1. DEVELOPMENT OF
HEART TUBE
SHREEYA NAIK
ROLL NO. -141

2. • Development of blood cells and circulatory system – later part of 3rd
week of gestation
• Heart and blood vessels are mesodermal in origin
• Progenitor heart cells lie in the epiblast, adjacent to the cranial end
of the primitive streak. From there, they migrate through the streak
and into the splanchnic layer of lateral plate mesoderm where they
form a horseshoe-shaped cluster of cells called the primary heart
field (PHF) .

3. PHF induced by the underlying endoderm to
form cardiac myoblasts and blood islands that
will form blood cells and vessels by the
process of vasculogenesis. With time, the
islands unite and form a horseshoe-shaped
endothelial-lined heart tube surrounded by
myoblasts. This region is known as the
cardiogenic region.

4. • CRANIOCAUDAL FOLDING • LATERAL FOLDING
Initially the cardiogenic area was anterior to
oropharyngeal membrane ,as a result of growth CNS
system and CRANIOCAUDAL FOLDING of the embryo the
oropharyngeal membrane is pulled forward ,while the
heart and pericardial cavity move to the cervical region
and gradually to the thorax
The lateral folding cause the two heart tubes to fuse
except at the caudal most ends .

5. • Thus the heart becomes a continuous expanded tube having inner endothelial
lining and outer myocardial layer.
• Heart tube attached dorsal side of pericardial cavity by fold of mesocardium
tissue –DORSAL MESOCARDIUM.
• With futher development the dorsal mesocardium disappears ,creating the
transverse pericardial sinus that connects both side of pericardial cavity
• HEART TUBE consist of 3 layers
1. Inner ENDOTHELIUM
2. Myocardium,muscular wall
3. Epicardium/visceral pericardium

6. ATRIAL END
VENOUS END
cordis

7. The cephalic portion of the tube bends ventrally,
caudally, and to the right and the atrial (caudal)
portion shifts dorsocranially and to the left. This
bending, creates the cardiac loop.
LOOPING OF HEART

8. Development Of Right
Atrium
Roll No - 143

9. •The main part of
Right Atrium is
derived from Right
half of Primitive
Atrium
•The Sinus Venosus
is absorbed into the
Right Atrium

10. •The left horn of the
Sinus Venosus
becomes Coronary
Sinus
•The Right common
Cardinal vein becomes
part of Superior Vena
Cava
•The right Vitelline vein
forms the Inferior Vena
Cava

11. Development Of The Conducting System
Of The Heart

12. •After fusion of the
two tubes the
pacemaker lies in
the Sinus Venosus
•Afterwards it comes
to lie near the
opening of SVC

13. •Similarly the AV Node and the AVBundle
form in the left wall of Sinus Venosus and
afterwards it comes to lie near the Interatrial
Septum

14. FORMATION OF
SEPTUM
INTERMEDIUM
Septum
Intermedium
.

15. Septum intermedium

17. Development Of Left Atrium
Roll no - 144
The left atrium is derived from :-
Left half of primitive atrial chamber
Left half of AV canal
Absorbed proximal parts of pulmonary
veins

18. Absorption of Pulmonary
Veins into Left Atrium
At first only one pulmonary
vein enters the atria
The proximal part of vein is
gradually absorbed and is
incorporated into the wall of
the atrium
As a result , four vein (two
on each side) finally open
into atrium

19. 6th Week
8th Week

20. Development of the ventricles
The part of the heart tube lying within the pericardial cavity grows rapidly
and, therefore, becomes folded on itself to form a “U”-shaped
bulboventricular loop.

21. Bulboventricular sulcus gradually becomes shallower so that the conus,
the proximal part of the bulbus cordis, and the ventricle, come to form one
chamber which communicates with the truncus arteriosus.

22. DEVELOPMENT OF INTER-ATRIAL SEPTUM
Beginning at the end of the fourth week, the primordial atrium is divided into
right and left atria by the formation and subsequent modification and fusion of
two septa

23. Septum primum
Begins at the end of the fourth week
Septum primum, a thin crescent shaped membrane

24. Grows toward the fusing endocardial cushions from the roof of the
primordial atrium, partially dividing the common atrium into right and
left halves.
Fused endocardial cushion

25. Before the foramen primum disappears, perforations, produced by
apoptosis, appear in the central part of the septum primum.

26. During the fifth and sixth weeks septum secundum, a thick
crescentic muscular fold, grows from the ventrocranial wall of the
right atrium, immediately adjacent to the septum primum

27. How does this septum formation helps to prevent backflow
of oxygenated blood?
Septum Primum - thin and mobile
Septum Secundum - thick and rigid

29. INTERVENTRICULAR SEPTUM
Roll No. 150

30. Interventricular Septum Divided into :-

31. • Muscular Part :-
• The Medial Walls of the expanding ventricles become apposed
and gradually merge forming the muscular interventricular septum
• Membranous Part :-
• Derived from Endocardial Cushions.
• Derived from Conus Septum.

32. Conus Septum :-
Heart Tube is divided into Bulbar Cordis , Primitive Ventricle , Primitive
Atrium , Sinus Venosus.
• Bulbus Cordis gets further divided into 3 parts :- Truncus Arteriosus ,
Conus Cordis and proximal part of Bulbus Cordis
Conus Cordis further develop Conus Swellings which gets further
developed into Conus Septum.
*Trunkus Arteriosus of Bulbus Cordis give rise to
aorta and Pulmonary Trunk seperated by
Spiral Septum.
*Proximal part of Bulbus Cordis give rise to
smooth parts of ventricle :-
Vestibule and Infundibulum.

34. Applied :- Tetralogy of Fallot
Anterior Displacement of Spiral Septum

35. Ventricular Septal Defect

36. Congenital
anomalies of
the heart
Roll no.146

37. (I) DEXTROCARDIA - (i) with situs inversus (ii) with laterality
1. CARDIAC LOOPING ANOMALIES

38. Normal Dextrocardia

39. 2. ATRIAL SEPTAL DEFECT (asd)

40. Normal Interatrial Septum Formation

41. Foramen Ovale
SP
SS
S
V
C
I
V
C

42. 1. Excess Resorption of Septum Primum
90% ASDs- Ostium Secundum Defects
Foramen
Ovale Ostium
Secundum

43. 2. Incomplete Development of Septum Secundum
ASDs- Ostium Secundum Defects
Foramen
Ovale Ostium
Secundum

44. Courtesy: MSD Manuals

45. Cor Triloculare Biventriculare

46. 3. Ventricular septal defect (VSd)
Normal Interventricular Septum Development
Muscular Region
Membranous Region

47. (I) Muscular region of IV Septum (II) Membranous region of IV Septum
Muscular Region
Membranous Region

48. 5. Tricuspid atresia
Normal Development of Atrioventricular Valves

49. (1) Underdevelopment of
Right Ventricle
(3) Ventricular Septal Defect
(4) Patent Foramen Ovale
Absence/Fusion of Tricuspid Valves
Normal Abnormal
(2) Left Ventricular Hypertrophy

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