Development of

the Cardiovascular System

Contents Establishment of the primordial cardio-

vascular system

Development of the heart

Blood circulation of fetus and circulatory

changes after birth

Congenital defects of the cardiovascular

system

Establishment of the Primordial

Cardiovascular System

Yolk sac mesenchyme cells

blood islands

Central C Peripheral C

Primitive Blood cell Endothelial C

Blood C Endothelial tubule

Endothelial tube meshwork

Endothelial tube network

appears in chorion and

body stalk, and connect to

vitelline circulation.

By the 18-20th days,

endothelial tube network

appears in intraembry-onic

mesenchyma to form

intraembryonic endothe-

lial tube network.

By the end of 3rd week,

intraembryonic and extra-

embryonic endothelial

tube networks connect to

each other.

Endothelial tube networks

fuse or disappear to form

primordial cardiovas-

cular system.

① cardiac tube:2 tubes1 tubeprimitive heart

② arteries

③ veins

20d

cardiac tubes

End of 4w

Primitive heart

4w

① cardiac tube

② arteries

③ veins

2 dorsal A 1 ,many branchesFew pairs of vitelline A1 pair of umbilical A6 pairs of aortic arches

20d 4w End of 4w

Dorsal A Dorsal A Dorsal aortaAortic arches

Umbilical AVitelline A

1 pair of anterior cardinal V 1 pair of posterior cardinal V1 pair of vitelline V1 pair of umbilical V

20d 4w End of 4w

Anterior cardinal V

Posterior cardinal V Umbilical VVitelline V Common cardinal V

Commoncardinal V

① cardiac tube ② arteries

③ veins

vitelline, umbilical and embryonic circulation.

• Development of the cardiac tube

• Morphogenesis of the heart

• Partitioning of heart chambers

Development of the Heart

Cardiogenic area

Oropharyngeal membrane

Cardiogenic area is anterior to

the ooropharyngealropharyngeal membrane.

Development of the cardiac tube

A. A cavity appears in the cardiogenic area

--pericardial cavity

B. Ventral of the cavity is cardiaogenic cords

--cardiaogenic plate

Pericardial cavity

cardiaogenic plate

18~19th day

C. cardiaogenic plate becomes hollow --cardiac tube

Pericardial cavity

cardiac tube

20th day

D. Cephalic folding:

Pericardial cavity: dorsal → ventral

Cardiac tube: ventral → dorsal

Pericardial cavity

cardiac tube

22nd day

E. Lateral folding: 2 cardiac tubes → single cardiac tube.

F. The tube remains attached to the dorsal side of the

pericardial cavity by the dorsal mesocardium.

G. The dorsal mesocardium breaks down to form the

transverse sinus, which connects both sides of the

pericardial cavity.

Cephalic end Arteries ， Caudal end Veins

Pericardial cavity

cardiac tube

Cephalic end Caudal end

Transverse sinus

Vein end

Cardiac tube

Artery end

The 21st d

Part of the cardiac tubes

merged

Cephalic end A

Caudal end V

Morphogenesis of the heart

atrium

ventricle

bulbus cordis

The 22nd d

Cardiac tubes almost

merged

Three expansions

Bulbus cordis

Ventricle

Atrium

The 4th expansion, the

sinus venosus appears

The truncus arteriosus

appears

The bulbus cordis and

ventricle grow faster

than other regions, the

cardiac tube starts to

bend.The 23rd d

atrium

bulbus cordis

truncus arteriosus

sinus venosus

ventricle

Form a ‘U’ like structure, the cardiac loop--bulboventricular loop.

The 24th d

sinus venosus

truncus arteriosus

The 35th d

atrium

Aortic arches

ventricle

The bulboventricular

loop continues to grow

and bend:

• Atrium shifts in dorso-

cranial direction and

bulges laterally on each

side of bulbus.

• Sinus venousus located

at caudal portion of

atrium

• Primary ventricle develop

into the left ventricle.

• The bulbus cordis

proximal portion develops

into the right ventricle.

• Atrioventricular canal:

atrioventricular junction

remains narrow.

The 35th d

atrium

Aortic arches

ventricle

The normal heart shape was established, but

partitioning has not completed.

Partitioning of Heart Chambers

Partitioning of atrioventricular canal

Partitioning of the primitive atrium

Partitioning of the primitive ventricle

Division of truncus arteriosus and bulbus

cordis

(from 27th day to 37th day)

Partitioning of atrioventricular canal

• Endocardiac cushion: • The endocardial cushions grow toward each other and fuse

Bicuspid

Ttricuspid

Endocardiaccushion

• Lateral atrioventricular cushion: form atrioventricular valve. Left → bicuspid, right → tricuspid

Foramen primum

Septumprimum

Endocardiaccushion

Partitioning of the primitive atrium

• Septum primum: a thin sickle-shaped crest appearing from dorso-cranial wall of atrium.

• Foramen primum: septum primum grows toward the endocardial cushions, leaving an opening between its lower edge and the endocardial cushions

End of the 4th w

Early 5th w

Small holes

Foramen primum

• Foramen secundum

Small holes fuse to

form the foramen se-

cundum,The foramen

primum closed.

• Septum secundum ：another membrane

appears on the right of

the septum primum. End of the 5th w

Septum primum

Foramen secundum

Septum secundum

Early 6th w

• Foramen ovale :

septum secundum

extends downward to

cover the foramen

secundum, but leaving

an opening.

• The septum primum

covers the foramen

ovale, serves as a

valve.

Foramen ovale

Septum secundum

Foramen secundum

Septum primum

• Before birth, blood can

flow from right atrium

toward the left atrium

• After birth, two septums

fuse , the foramen ovale

closed complete, and

atrium is separated into

R and L atria.

The 4th w

EC• The muscular

Interventricular

septum grows

up from the floor

of the ventricle.

RV

LV

Inter-ventricular septum

Partitioning of the primitive ventricle

• Interventricular foramen

the muscular interven-

tricular septum keeps

growing toward endo-

cardial cushions, but left

an opening, called inter-

ventricular foramen.

End of the 5th w

EC

Inter-ventricular foramen

IV septum

• Membranous interventricular septum:

Derived from right bulbar ridge, left bulbar ridge and the

endocardial cushion,closes the interventricular foramen

endocardial cushions

Membranous interventricular septum

End of the 7th w

The interventricular septum:

muscular partion + membranous portion

Left ventricle Pulmonary artery

Right ventricle Aorta

The 5th w

Bulbus

cordis

Truncus arteriosus

Truncal ridge

Bulbar ridge

• Two spiral truncal ridges/ bulbar ridges grow from the

inner walls of the truncus arteriosus and bulbus cordis.

Division of truncus arteriosus and bulbus cordis

• These ridges twist around each other and fuse to

form a spiral aorticopulmonary septum.

Pulmonaryartery Aortico-

pulmonary septum

Aorta

• The ridges spiral neatly down the truncus until they reach the ventricles.

• As the same time, the division of the ventricle is completed.• Aorticopulmonary septum divides truncus arteriosus and

bulbus cordis into two channels: pulmonary trunk

connecting to the right ventricle; aorta connecting to the left

ventricle.

Blood circulation of fetus

and circulatory changes after birth

Before birth

Placental circulation: umbilical A. & V.

Blood circulation of fetus

a.Umbilical A: distal parts becomes into medial umbilical ligament, but proximal portions persist as superior vesical arteries.

b. Umbilical V and ducts venousus: constrict and becomes into ligamen-tum teres hepatis and ligamentum venosus

c. Ductus arteriosus: constrict and become ligamentum arteriosum

d. Foramen ovale closed

Circulatory changes after birth

Congenital defects of

the cardiovascular system

Atrial septal defect

An atrial septal defect (ASD) is a common congenital

heart anomaly.

The most common form of ASD is patent oval foramen.

Consequently there is a mixing of oxygenated and

deoxygenated blood.

Atrial septal defect

A. Perforation of valve of

ovale foramen

B. Excessive resorption of the

septum primum

C. Inadequate development of

the septum secundum.

D.B+C

Endocardial cushion defect with septum primum defect

Ventricular septal defect Muscular part of the ventricular septum: sparsely Membranous part of the ventricular septum defect:commonly

Unfused endocardial cushion,bulbar ridge and muscular septum or over absorption of membranous septum

Ductus arteriosus fails to be closed after birth. Isolated or combined with other defects. Blood will be shunted from the aorta to the lungs, eventually causing irreversible pulmonary hypertension.

Patent ductus arteriosus

Persistent truncus arteriosus

Aorticopulmonary septal

ridges fail to fuse and descend;

Truncus overrides both

ventricles;

Accompanied by ventricular

septal defect;

Resulting in cyanotic defect.

Transposition of great vessels

Aorticopulmonary 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

Tetralogy of Fallot

A complex of 4 defects:

Pulmonary stenosis

Overriding aorta

Ventricular septal defect

Hypertrophy of the right

ventricle

Unequal division of the truncus and bulbus

Morphogenesis of the heart

Partitioning of atrioventricular canal, autrium, ventricle, and truncus arteriosus and bulbus cordis

Congenital defects of the cardiovascular system （ Tetralogy of Fallot ）

Key points

Prepare for

Development of Urogenital System