EMBRYOLOGY CVS – PART I

CVS Embryology 1

• 1st system to function in embryo

• Circulation of blood : 3rd week

• Derived from mesenchyme

EMBRYOLOGY : CVS

CVS Embryology 1

EMBRYOLOGY : CVS

CVS Embryology 1

• Mesenchymal cells in splanchnic mesoderm proliferate &

form cell clusters : Angiogenic clusters

EMBRYOLOGY : CVS

• Angiogenic cell cluster

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CVS Embryology 1

• Angiogenic clusters on lateral side then

spread rapidly in cephalic direction

caudal

cephalic

EMBRYOLOGY : CVS

CVS Embryology 1

• Angiogenic clusters form horseshoe shaped plexus of blood vessels

• Anterior central part of plexus : Cardiogenic area

EMBRYOLOGY : CVS

CVS Embryology 1

Heart Development

• Develops from splanchnic mesenchyme in cardiogenic area.

EMBRYOLOGY : CVS

Cardiogenic area

EMBRYOLOGY : CVS

EMBRYOLOGY : CVS

The Pericardial cavity

CVS Embryology 1

CVS EMBRYOLOGY

Bilateral cardiogenic cords:

• Formed from mesenchyme

• Cords canalized

• Form paired endocardial heart tubes

• Endocardial tubes fuse into single heart tube forming primitive heart

CVS EMBRYOLOGY

CVS Embryology 1

Fusion of primitive heart tubes

CVS EMBRYOLOGY

PRIMITIVE HEART

• Heart tube elongates & bends

• Cephalic portion : bend in ventral & caudal direction & to right

• Caudal portion : bends to left

CVS Embryology 1

• Bending creates cardiac loop

PRIMITIVE HEART

CVS Embryology 1

• The cardiac loop

EMBRYOLOGY : CVS

EMBRYOLOGY : CVS

Future heart develops dilatations & constrictions : results in 4 chambers:

• sinus venosus

• primordial atrium

• primodial ventricle

• bulbus cordis

CVS Embryology 1

ACV: Anterior cardinal vein

PCV: Posterior cardinal vein

UV : Umbilical vein

VIT: Vitelline vein

EMBRYOLOGY : CVS Sinus Venosus

• Maintain paired condition longer

than any other portion of heart

tube

• Each horn receives the vitelline v,

umbilical v, common cardinal v

CVS Embryology 1

Sinus venosus receives:

• umbilical veins from the chorion.

• vitelline veins from the yolk sac

• common cardinal veins from the embryo.

CVS Embryology 1

EMBRYOLOGY : CVS Sinus Venosus

EMBRYOLOGY : CVS Sinus Venosus

Inferior portion of right sinus

develops into 2 parts:

• Valve of inferior vena cava

• Valve of coronary sinus

CVS Embryology 1

EMBRYOLOGY : CVS Sinus Venosus

• Wk 4 consist of small transverse

portion & L & R sinus horns

CVS Embryology 1

EMBRYOLOGY : CVS Sinus Venosus

EMBRYOLOGY : CVS Sinus Venosus

EMBRYOLOGY : CVS Sinus Venosus

• At 1st communication between sinus & atrium is wide

• With obliteration of the left umbilical vein , the left sinus

horn loses its importance

CVS Embryology 1

• develops a left horn which becomes the coronary sinus & a right horn which will be incorporated

into right atrium

EMBRYOLOGY : CVS Sinus Venosus

CVS Embryology 1

EMBRYOLOGY : CVS Sinus Venosus

Remnant of the left sinus venosus :

• Oblique vein of left atrium

• Coronary sinus

CVS Embryology 1

• Bulbus cordis & ventricle grow faster

EMBRYOLOGY : CVS

CVS Embryology 1

• Heart bends upon

itself, forming a

bulboventricular loop

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CVS Embryology 1

• bulboventricular loop

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CVS Embryology 1

• Intro to atrium & sinus

• Atrium & sinus venosus come to lie dorsal to bulbus cordis, truncus arteriosus &

ventricle

• At the same time, heart invaginates into pericardial cavity

• Dorsal mesocardium which attaches it to dorsal wall of pericardial cavity degenerates &

forms tranverse pericardial sinus

EMBRYOLOGY : CVS

CVS Embryology 1

Truncus Arteriosus

• Continues caudally with bulbus

cordis

• Enlarges cranially to form aortic sac

from which aortic arches arise

CVS Embryology 1

EMBRYOLOGY : CVS Truncus Arteriosus

• Enlarges cranially to form aortic sac

from which aortic arches arise

EMBRYOLOGY : CVS Truncus Arteriosus

EMBRYOLOGY : CVS THE ATRIA

Fate of adult Left Atrium

• Formed by incorporation of primitive pulmonary veins

• As atrium enlarges, parts of vein & its branches absorbed

CVS Embryology 1

• Primitive pulmonary vein & its 4 main branches become partially incorporated into left atrium = 4

pulmonary veins.

EMBRYOLOGY : CVS

CVS Embryology 1

Result

• 4 pulmonary veins entering adult left atrium

• Smooth walled part of left atrium derived from absorbed pulmonary vein tissue

• Left auricle derived from primitive atrium

EMBRYOLOGY : CVS

CVS Embryology 1

EMBRYOLOGY : CVS

Development of the smooth-walled portions of the right and left atrium.

Both the wall of the right sinus horn (blue) and the pulmonary veins (red) are

incorporated into the heart to form the smooth-walled parts of the atria.

EMBRYOLOGY : CVS

Cardiac septation

End of 4th wk, 2 mesenchymal cushions, the atrioventricular endocardial cushions,

appear at the superior and inferior borders of the atrioventricular canal

In addition, 2 lateral atrioventricular cushions appear on the right and left borders of the canal

EMBRYOLOGY : CVS Cardiac septation

EMBRYOLOGY : CVS

Cardiac septation

EMBRYOLOGY : CVS

CVS Embryology 1

• End of 4th week, sickle shaped crest grows from roof of atrium : Septum

Primum

• Opening between septum primum & endocardial cushion: ostium primum

• Limbs of septum extend in direction of endocardial cushions

EMBRYOLOGY : CVS

CVS Embryology 1

EMBRYOLOGY : CVS

• Crescent shaped fold : septum secundum

• Never forms complete partition in atrial cavity

• Free concave edge overlaps ostium secundum

CVS Embryology 1

EMBRYOLOGY : CVS

• Opening left by septum secundum : Oval foramen

CVS Embryology 1

• Before birth foramen ovale allows blood to pass from right atrium into left atrium; reflux is

prevented by the valve. After birth foramen ovale normally closes by fusion of septum primum &

septum secundum.

EMBRYOLOGY : CVS

CVS Embryology 1

EMBRYOLOGY : CVS

CVS Embryology 1

• During week 5, bulbus cordis & truncus arteriosus become divided by an aorticopulmonary

septum into pulmonary trunk & aorta.

EMBRYOLOGY : CVS

• During week 5, bulbus cordis & truncus arteriosus become divided by an aorticopulmonary

septum into pulmonary trunk & aorta.

EMBRYOLOGY : CVS

• Ventricles become partitioned by a crescentic fold which is open cranially until end of week 7.

EMBRYOLOGY : CVS

CVS Embryology 1

EMBRYOLOGY : CVS

CVS Embryology 1

• Primitive ventricle : give rise to most of left ventricle

EMBRYOLOGY : CVS

• Bulbus cordis : forms most of right ventricle

CVS Embryology 1