1

The Cardiovascular System (Part I)

黃敏銓

解剖學暨細胞生物學研究所

Congenital heart defects(CHDs)

台灣兒童心臟學會

Sinus venarum

Membranous

septum

Conus arteriosus

(infundibulum)

Aortic vestibule

4

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

5

The cardiovascular system is

derived mainly from:

• Mesoderm

– First / Primary heart field (FHF)

– Second / Secondary heart field (SHF): from

pharyngeal mesoderm

• Neural crest cells

J Cardiovasc Dev Dis. 2015 Dec; 2(4): 248–272.

6

Angioblastic cord

Heart primordium

Angioblastic cord18 days

Early development of the heart

7

Fusion of endocardial heart tubes

Ventral views

8

Primordial myocardium (from splanchnic mesoderm)

Cardiac jelly

Pericardial coelom

22-day

20-day

Fusion of endocardial heart tubes

Dorsal mesocardium

Epicardium

9

Truncus arteriosus

Bulbus cordis

Primordial ventricle

Primordial atrium

Sinus venosus

U-shaped bulboventricular loop

24 days

有不同命名方式

10

Circulation through primordial heart

1

2

3

4

5

6

Sinus venosus

End of 4th week: unidirectional flow

11

Partitioning of primordial heart

• begins around middle of the 4th week.

• is completed by the end of the 8th week.

• includes partitioning of:

– Atrioventricular canal

– Primordial atrium

– Primordial ventricle

12

Partitioning of Atrioventricular Canal

Endocardial cushions

(from cardiac jelly)

End of 4th week

5th week

Fused endocardial cushions

Left AV canal

Transformed endocardial cushions also contribute to the formation of valves and membranous septa of the heart.

13

AV endocardial cushions

the primordia of the valves and membranous septa

Bone morphogenetic protein (BMP2)

14

Partitioning of primordial atrium

• begins at the end of the 4th week.

• is divided into right and left atria by:

– Septum primum

– Septum secundum

15

Septum primum

Septum primum

Endocardial cushion

Foramen primum(Ostium primum)

Foramen secundum(Ostium secundum)

Septum secundum

16

Septum primum

Foramen primum

Septum primum

Foramen primum

Foramen secundum

Foramen primum

Foramen secundum

Septum primum

Septum secundum

17

Septum secundumSeptum secundum (upper limb)

Valve of oval foramen(from septum primum)

Oval foramen

Foramen secundum

Oval foramen

Valve (from septum primum)

5th~6th week

18

Valve of oval foramen

Septum primum

Valve of oval foramen

Oval foramen(open)

Septum secundum

19

Before birth After birth

Oval foramenOval fossa

Septum primum(valve of oval foramen)

Septum secundum

Oval fossa is a remnant of oval foramen

20

Development of sinus venosus

Left horn of sinus venosus Right horn of sinus venosus

Opening of sinus venosus into primordial atrium

Dorsal view (4th week)

RightLeft

21

Progressive enlargement of the right horn results from two left-to-right shunts of blood

Dorsal view (7 weeks)RightLeft

22

Right horn of sinus venosus

Left horn of sinus venosus

Sinus venarum of right atrium

Coronary sinus

Primordial atrium

Doral view

26 days

8 weeks

RightLeft

23

Right sinuatrial valve →• Crista terminalis• Valve of IVC• Valve of coronary sinus

Crista terminalis

Valve of inferior vena cava

Valve of coronary sinus

Left sinuatrial valve →fused with septum secundum →Interatrial septum

Right Left

24

Absorption of the pulmonary vein into the left atrium

6 weeks5 weeks

8 weeks

Smooth-walled part of left atrium

Left auricle

Primordial left atrium

Primordial pulmonary vein

Right Left

Cardiovasc Res (2002) 54 (2): 287-294.

The role of pulmonary veins in atrial fibrillation

(Pharmacol Ther. 2009 Nov;124(2):207-18.)

http://www.doctortipster.com/

myocardial sleeves of pulmonary veins

心房顫動(atrial fibrillation)Pulmonary vein ablation

26

Partitioning of primordial ventricle

Interventricular septum(muscular part)

Interventricular foramen

Fused endocardial cushions

5th week

Expansion

Right Left

27

Bulbus cordis incorporates into the walls of ventricles

Conus arteriosus(infundibulum)

Aortic vestibule

5 weeks 6 weeks

Aortic vestibule

Membranous septum

Membranous part of IV septum

29

Closure of the interventricular foramen

Right bulbar ridge

Fused

endocardial

cushions

Membranous part of IV septum

7 weeks

Left bulbar ridge

30

Cavitation of the ventricular walls forms a sponge-work of muscular bundles – trabeculae carneae

Trabeculae carneae

Chordae tendinae

Papillary muscle

5 weeks 6 weeks

7 weeks

20 weeks

Right Left

31

Partitioning of Bulbus Cordis and Truncus Arteriosus

Truncal ridge

Bulbar ridge

Truncus arteriosus

Bulbus cordis

Pulmonary trunk

Aorta

Aorticopulmonary septum

5 weeks

6 weeks

32

Spiral form of Aorticopulmonary Septum

Development of cardiac valves (semilunar valves)

Dorsal valve swelling

Ventral valve swellingBulbar ridges

Swellings of subendocardial tissue

33

34

Valve swelling

Hollowing and thinning of valve swellings

35

Cardiac conduction system

Sinuatrial (SA) node (5th week)

Atrioventricular (AV) node

Atrioventricular bundle

Branches of AV bundleRight Left

Sinus venosus

Fetal circulation

Ductus venosus

Ductus arteriosus

Foramen ovale

Sphincter

36

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: Oxygen, bradykinin, indomethacin (PGE2 inhibitor)

• Open: Hypoxia, PGE2, prostacyclin (PGI2)

4. The umbilical arteries constrict.37

Ligamentum teres(umbilical vein)

Ligamentum venosum(ductus venosus)

Ligamentum arteriosum(Ductus arteriosus)

Oval fossa(Foramen ovale)

Medial umbilical ligament(umbilical artery, distal)

Superior vesical artery (umbilical artery, proximal)

Adult Derivatives of fetal vascular structures

38