1. Circulation system
陳建榮

2. Normal development of Heart
Early Events
Migration of cardiogenic mesenchyme
Differentiation of mesenchyme
Chamber formation
Folding of the heart tube
Critical Changes
Vascular Changes

3. Migration of cardiogenic mesenchyme

4. 血管母細胞索

5. Differentiation of mesenchyme
The early heart is a simple tube which commences beating during the third week (Day 21-22).
Cardiogenic mesenchyme differentiates into three distinct cell populations:
Endocardium 心內膜
Myocardium 心肌
Epicardium 心外膜

6. Cell Population
 Functions and Fates
 Endocardium
Endothelial lining
Connective tissue precursor (Valves and fibrous skeleton)
 Myocardium
Myocytes
Conduction system (Purkinje fibres)
Myoendocrine cells (Atrial Natriuretic Factor production)
Epicardium
Coronary vessel precursors
Visceral pericardial lining

8. Early heart chambers
 Sinus venosus (SV)
靜脈竇
This is the collecting compartment of the heart. Oxygenated blood from the placenta and deoxygenated blood from embryonic tissues are mixed in the sinus.
 Primitive atrium (PA)
心房原基
This is the compartment destined for further partition to the definitive atria.
 Primitive ventricle (PV)
心室原基
This is the compartment destined for further partition to the definitive ventricles.
 Bulbus cordis (BC) 心球
This will contribute to the pulmonary trunk and aorta, along with the truncus arteriosus.
 Truncus arteriosus (TA)
動脈幹
This will contribute to the aortic arches.
 Fibrous skeleton (FS)
纖維骨架
This is the area of connective tissue proliferation, site of future valves.

9. Folding of the heart tube
Apoptosis in the dorsal mesocardium will allow movement of the early heart tube within the pericardial cavity

10. The folding of the heart tube brings the inflow and outflow trunks in an adjacent position at the superior aspect of the developing heart.

11. The dorsal fold forms the two pericardial sinuses and places the fibrous skeleton in a single plane

12. Inflow and outflow trunks are positioned posteriorly as a result of the dorsal fold

14. Normal development of Heart
Early Events
Critical Changes
Endocardial cushion（心內墊） growth and fusion
Bulboventricular looping
Interatrial septum（心房間隔） formation
Interventricular septum（心室間隔） formation
Aortico-pulmonary septum（主肺動脈隔） formation
Vascular Changes

15. Endocardial cushion fusion
Endocardial cushions are areas of the fibrous skeleton forming between the atrium and ventricle.
Endocardial cushions serve two important functions:
form a partition in the heart tube between the atrium (PA) and ventricle (PV) (tricuspid and bicuspid valves)
provide a "scaffold" of the interatrial septae and the interventricular septum
Defects in endocardial cushion fusion are associated with trisomies 18 and 21 (Down's syndrome).

16. Valvular atresia
Valvular atresias arise from the uneven partition of the AV canal. Depending on the size and position of the narrowed channel, a tricuspid atresia or a biscuspid atresia results. Atresias arising from anomalous partition of the canal are referred to as congenital atresias

17. Bulboventricular looping
BV looping is a consequence of several changes:
- Dorsal folding
The first dorsal fold forms an expanded primitive ventricle, referred to as the bulboventricular loop.
- Ventricular growth
Differential growth of the proximal ventricular tissue causes a counter-clockwise rotation of the folded heart tube. The site of ventricular growth marks the future left ventricle. Abnormal growth of the distal primitive ventricle causes clockwise rotation, an anomaly known as dextrocardia心偏右.
- AV canal房室管 partitioning
The Atrio-Ventricular (AV) canal between the primitive atrium and ventricle has now been partitioned by the fusing endocardial cushions.
- Shunting of venous return
The development of the venous system causes an increase in right-sided venous return to the primitive atrium. Combined with the partitioning of the AV canal, the change in blood flow volume and directions assists in the outgrowth of the left ventricle.

22. Looping anomalies(dextrocardia)

23. Interatrial septum formation
Blue arrows - direction of growth;
Red arrow - direction of blood flow; ECC - endocardial cushion;
RA - right atrium;
LA - left atrium.

24. 原隔 原孔 次孔 次隔

26. Fossa ovalis卵圓窩

27. Atrial septal defects心房間隔缺損 (ASD)
Atrial septal defects (ASD) are fairly common, present in 10-15% of patients with congenital cardiac anomalies. It is more commonly observed in females than males (2-3:1).

29. Formation of left atrium

30. Interventricular septum formation
AP - aorticopulmonary;
ECC - endocardial cushion; Blue arrow - direction of bulbar ridge growth; Red arrow - direction of ventricular growth
 IVS Part
Origin
muscular
ventricular wall
membranous
fused bulbar ridges 球狀脊
fused endocardial cushions

31. 球狀脊

32. 室間孔

33. Ventricular septal defects心室間隔缺損(VSD)

34. Atrioventricular septum defect房室瓣缺損

35. Aortico-pulmonary septum formation
The aortico-pulmonary (AP) septum arises within the truncus arteriosus. The septum results from the downwards growth and fusion of bulbar ridges, induced by invasion of neural crest cells. The AP septum serves to divide the ventricular outflow between the pulmonary artery and the ascending aorta

39. Tetralogy of Fallot
The tetralogy of Fallot results from the asymmetric division of the AP septum. The result is a stenosed pulmonary artery and a VSD.
Tetralogy of fallot:
Pulmonary valve stenosis
Ventricular septal defect
Overriding aorta
Hypertrophy of right ventricle

40. Eisenmenger's syndrome
Characteristics of Eisenmenger's syndrome:
persistent truncus arteriosus
ventricular septal defect
left-right ventricular shunt
right ventricle hypertrophy

41. Normal development of Heart
Early Events
Critical Changes
Vascular Changes
Overview of embryonic circulatory system
Venous development
Arterial development
Anatomical correlations

42. Overview of embryonic circulatory system

46. Venous system development

50. Arterial system development

52. Aortic arch derivatives
動脈韌帶
動脈導管

53. Recurrent laryngeal n. and 6th aortic arch

54. Coarctation of aorta
主動脈弓緊縮

56. Right arch of aorta

57. Anomalies of right subclavian artery

58. Anatomical correlations

61. Ductus arteriosus

62. Patent ductus arteriosus
Blue-pulmonary trunk; Red-aorta and tributaries; Green-patent ductus arteriosus

63. Embryologic Structure
Adult Equivalent
Left anterior cardinal vein
disappears proximally
distal portion contributes to Left superior intercostal vein
anastomoses with Right anterior cardinal vein distally to form Left brachiocephalic vein
 Left common cardinal vein
oblique vein of left atrium
 Left posterior cardinal vein
disappears
 Left horn of sinus venosus
coronary sinus
 Right anterior cardinal vein
 superior vena cava
Right common cardinal vein
superior vena cava
Right posterior cardinal vein
azygous vein
Primitive atrium
right auricle
Foramen ovale
fossa ovalis and limbus
 First aortic arch
maxillary artery
contribution to external carotid artery
 Second aortic arch
 persists dorsally as stapedial artery
 Third aortic arch
proximal portions form common carotid artery
distal portions form internal carotid artery
 Fourth aortic arch
left arch (with aortic sac) forms ascending aorta and arch
right arch contributes to right subclavian artery
 Fifth aortic arch
 does not persist
 Sixth aortic arch
proximal left arch - left pulmonary artery
distal left arch - ligamentum arteriosum
proximal right arch - right pulmonary artery
distal right arch - does not persist
 Ductus venosus
ligamentum venosum
Left umbilical vein
ligamentum teres distally
degenerates proximally
portion within septum transversum contributes to hepatic portal system
Right umbilical vein
degenerates proximally and distally
 Left vitelline vein
fuses with right vitelline vein to form portal vein
 Right vitelline vein
fuses with left vitelline vein to form portal vein

64. Development of lymphatic system