1. Heart Development
Dr. Nimir

2. Objectives:
Understand early development of blood vessels.
Basic understanding of the early stages of heart development.
Describe the formation and position of the heart tube.
Discus the development of sinus venosus.
Describe partioning by septa and chambers formation.
Discus congenital malformations.
Gain knowledge of fetal circulation.

3. 1. Development of Early Blood Vessels
1.1 Yolk sac → blood islands → endothelia → vessels
primitive blood cells.

4. 1.2 Chorion, body stalk, embryonic body → blood vessels → 3 separate circulations: vitelline, chorionic, and intraembryonic.

5. 2. Development of Primitive Heart Tube
2.1 Primordium: Cardiogenic area →
Intraembryonic coelom → pericardial coelom;
2 lateral cardiogenic plates →endocardial heart tubes.

6. 2.2 Primitive heart tube
1) Lateral fold: 2 heart tubes → single heart tube.

7. 2) Head fold: pericardial coelom → ventral to heart tube
↘caudal to oropharyngeal membrane

8. 3) Wall of primitive heart tube
Endocardial heart tube → endocardium
Myoepicardial mentle → myocardium, epicardium
Cardiac jelly → subendocardial tissue

9. 3. Formation of Heart Loop
3.1 Heart tube → bulbus cordis, ventricle, atrium → truncus arteriosus, conus cordis, ventricle, atrium, sinus venosus

10. 3.2 Bulboventricular portion → bulboventricular loop → cephalic portion bends ventrally, caudally and slightly to the right
3.3 Atrium → dorsocranially and bulges laterally on each side of bulbus
3.4 Proximal part of bulbus → primitive right ventricle

11. 4. Partitioning of Heart Chambers
4.1 Division of atrioventricular canal
Subendocardial tissue → 2 endocardial cushions → fuse → right and left canals

12. Formation of atrioventricular valves

13. 4.2 Partitioning of primitive atrium
1) Septum primum → endocardial cushions → foramen primum.

14. 2) Septum primum absorbed → foramen secundum → foramen primum closing
3) Septum secundum → cover the foramen secundum → foramen ovale

15. 4) Blood from right to left atrium
foramen ovale

16. 4.3 Development of sinus venosus
Right horn enlarges (due to left-to-right shunts of blood in venous system)
Sinus-atrial orifice → right;
Receives sup. and inf. vena cava;
Right horn → right atrium (smooth walled part).

17. 2) Left horn degenerates → coronary sinus, oblique vein of left atrium;
Pulmonary vein and its branches → left atrium (smooth walled part)

18. 4.4 Partitioning of the primitive ventricle
1) Apical ventricle wall → muscular interventricular septum → interventricular foramen

19. 2) Endocardial cushion, right and left bulbar ridges → membranous interventricular septum → interventricular foramen closed

21. 4.5 Division of truncus and bulbus
Truncal ridges + Bulbar ridges →
aorticopulmonary septum

22. 2) Aorticopulmonary septum → spiral course →
pulmonary trunk → right ventricle
aorta → left ventricle

23. 3) Truncus swellings → hollowed out at upper surface → semilunar valves

24. 5. Circulation before and after Birth
5.1 Circulation before birth
Placental circulation: umbilical A. & V.
ductus venosus
foramen ovale
ductus arteriosus

25. 5.2 Changes after birth
Umbilical arteries → lateral umbilical ligaments
Umbilical vein → ligamentum teres hepatis
Ductus venosus → venous ligament
Ductus arteriosus → arterial ligament
Foramen ovale → oval fossa

26. 6. Congenital Malformations
6.1 Atrial septal defect
Excessive resorption of the septum primum;
Inadequate development of the septum secundum.

27. 6.2 Ventricular septal defect
Defect of the membranous septum, isolated or associated with other abnormalities.

28. 6.3 Tetralogy of Fallot
Unequal division of conus cordis;
4 defects: pulmonary stenosis, overriding aorta, ventricular septal defect, hypertrophy of right ventricle;
Causing cyanosis.

29. 6.4 Persistent truncus arteriosus
Truncoconal ridges fail to fuse and descend;
Truncus overrides both ventricles;
Accompanied by ventricular septal defect;
Cyanosis, blood to lungs increased.

30. 6.5 Transposition of great vessels
Truncoconal 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.

31. 6.6 Patent ductus arteriosus
Ductus arteriosus fails to be closed after birth;
Isolated or combined with other defects.

32. 6.7 Tricuspid atresia
Absence or fusion of tricuspid valves;
Patent oval foramen & ventricular septal defect;
Underdeveloped right ventricle

33. 6.8 Pulmonary valvular atresia (or stenosis)
Pulmonary valves are fused for variable distance;
Hypoplastic right heart;
Patent oval foramen and patent ductus arteriosus.

34. 6.9 Aortic valvular atresia and stenosis
Aortic valves are fused for variable distance;
Aorta, left ventricle, left atrium underdeveloped;
Accompanied by patent ductus arteriosus.

35. Thank You