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Home , Aorticopulmonary septum, Endocardial cushions, Fetal circulation, Foramen secundum, Septum primum, Septum secundum

The Cardiovascular System (Part I) 黃敏銓

解剖學暨細胞生物學研究所

1 補充

Congenital defects (CHDs)

台灣兒童心臟學會 補充 Sinus venarum

Membranous septum

Conus arteriosus (infundibulum)

Aortic vestibule The Cardiovascular System

1. The first major system to function 2. The primordial heart and vascular system appear in the middle of the third week 3. The heart starts to function (beat) at the beginning of the fourth week

4

The cardiovascular system is derived mainly from: • Splanchnic mesoderm – First / Primary heart field (FHF) – Second / Secondary heart field (SHF): from pharyngeal mesoderm • Neural crest cells

J Cardiovasc Dev Dis. 2015. 2: 248 6 Early development of the heart

Angioblastic cord

18 days Angioblastic cord

7

Fusion of endocardial heart tubes

Pericardial coelom 20-day

Dorsal mesocardium

Epicardium

Cardiac jelly 22-day Primordial myocardium (from splanchnic mesoderm) 9

Fusion of endocardial heart tubes

Ventral views

11 U-shaped bulboventricular loop

Primordial

有不同命名方式

Bulbus cordis

Primordial

24 days 12 Circulation through primordial heart

6

Sinus venosus 1

2

3

5

4 End of 4th week: unidirectional flow 13 Partitioning of primordial heart

• begins around middle of the 4th week. • is completed by the end of the 8th week. • includes partitioning of: – – Primordial atrium – Primordial ventricle

14 Partitioning of Atrioventricular Canal

5th week

Fused

1 3

End of 4th week

Endocardial cushions Left AV canal Fused endocardial cushions 2 4

15 AV endocardial cushions contribute to the formation of AV canal, AV valves and septa of the heart Endocardial cushions

AV endocardial cushion Conotruncal (truncobulbar) endocardial cushion

Cardiac jelly

Progress in Biophysics and Molecular Biology, 17 2018, Pages 95-110 Partitioning of primordial atrium

• begins at the end of the 4th week. • is divided into right and left atria by: – –

18 Septum primum

Septum primum

Endocardial cushion 1 2

Septum secundum

Foramen secundum (Ostium secundum)

Foramen primum (Ostium primum) 3 4 19 Septum primum

Septum primum

Foramen primum

Foramen primum

Foramen secundum

Foramen primum

Septum secundum

Foramen secundum

Septum primum

20 Septum secundum

Septum secundum (upper limb) 5th~6th week Foramen secundum Oval foramen

Valve of oval foramen (from septum primum)

Oval foramen

Valve (from septum primum)

21 Valve of oval foramen

Septum primum

Septum secundum

Oval foramen (open)

Valve of oval foramen

22 Oval fossa is a remnant of oval foramen

Before After birth

Septum secundum

Oval fossa Oval foramen Septum primum (valve of oval foramen)

23 Development of sinus venosus

primordial atrium Opening of sinus venosus into primordial atrium

Left Right

Left horn of sinus venosus Right horn of sinus venosus

Dorsal view (4th week) 24 Progressive enlargement of the right horn results from two left-to-right shunts of

Dorsal view (7 weeks)25 Left Right Doral view

Primordial atrium

26 days Right horn of sinus venosus

Left horn of sinus venosus

Sinus venarum of right atrium 8 weeks

Coronary sinus

26 Left Right Right sinuatrial valve → Left sinuatrial valve → • Crista terminalis fused with septum secundum → • Valve of IVC • Valve of coronary sinus

Crista terminalis

Valve of coronary sinus

Valve of inferior vena cava 27 Right Left Absorption of the pulmonary vein into the left atrium

5 weeks 6 weeks

Primordial pulmonary vein

Primordial left atrium 1 3

Smooth-walled part of left atrium

Left auricle 2 4 8 weeks 28 Right Left The role of pulmonary veins in atrial fibrillation (Pharmacol Ther. 2009.124:207)

心房顫動(atrial fibrillation) Pulmonary vein ablation myocardial sleeves of pulmonary veins

http://www.doctortipster.com/ Cardiovasc Res. 2002. 54: 287 Partitioning of primordial ventricle

Fused endocardial cushions

Interventricular foramen Expansion 5th week (muscular part)

30 Right Left incorporates into the walls of ventricles

Conus arteriosus (infundibulum)

Aortic vestibule

5 weeks 6 weeks

31 Closure of the interventricular foramen Membranous part of IV septum

Right bulbar ridge Left bulbar ridge

Fused endocardial cushions

32 7 weeks Cavitation of the ventricular walls forms a sponge-work of muscular bundles –

Trabeculation Compaction

5 weeks 6 weeks

20 weeks

Chordae tendinae 7 weeks Trabeculae carneae 33 Right Left Partitioning of Bulbus Cordis and Truncus Arteriosus

Truncus arteriosus Truncal ridge Bulbus cordis

Bulbar ridge 5 weeks

Aorta Pulmonary trunk

6 weeks

34 Spiral form of Aorticopulmonary Septum

35 Development of cardiac valves (semilunar valves) Swellings of subendocardial tissue: endocardial cushions Dorsal valve swelling

Bulbar ridges Ventral valve swelling

36 Hollowing and thinning of valve swellings

Valve swelling

37 Cardiac conduction system

Sinus venosus Sinuatrial (SA) node (5th week)

Atrioventricular (AV) node

Atrioventricular of AV bundle Right Left 38

Ductus arteriosus

Foramen ovale

Ductus venosus

Sphincter

39 Adult derivatives of fetal vascular structures Ligamentum arteriosum () Oval fossa ()

Ligamentum venosum ()

Ligamentum teres ()

Superior vesical artery (, proximal)

Medial umbilical ligament (umbilical artery, distal) 40 Transitional Neonatal Circulation

1. Alteration of the lungs • Fall in pulmonary vascular resistance • Increase pulmonary blood flow • Thinning of walls of pulmonary arteries 2. The oval foramen closes. • Higher left atrium pressure • Thicker left ventricular wall by the end of 1st month 3. The ductus arteriosus constricts.

• Close: , bradykinin, indomethacin (PGE2 inhibitor)

• Open: Hypoxia, PGE2, prostacyclin (PGI2) 4. The umbilical arteries constrict. 41