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Flashcards in Embryology Deck (18):

What happens in week 3

In week 3:
1-Blood vessels appear in Yolk sac, Chorion, Allantois connecting system
2- Angioblastic strands appear in cardiogenic mesoderm
3- They canalise to form primitive heart tubes
4- These fuse with blood vessels from other systems to form: PRIMORDIAL CARDIOVASCULAR SYSTEM


What is part of the primordial cardiovascular system?

1- Trunchus anterior
2-Bulbus Cordis
5-Sinus Venosum


What is the Trunchus anterior?

Caudal part of the heart
Arterial end of the heart
Continues with aortic sac from which aortic branches rise


What is the sinus venosum?

Cranial end
venous end
2 horns
supplied by the :
-vitelline vein- yolk sac
-umbellicul vein- placenta
-common cardinal vein- body of the embryo


What is the bulbogenic loop?

The bulbis cordis and the ventricle grow faster that the other components of the primordial cvs so the loop around



occurs round day 27-37
1- partitioning of the AV canals- ENDOCARDINAL CUSHION FORMATION
2- partitioning of the atria and the ventricles


Partitioning of the atria

1- septum primum
2- foramen primum- between septum premium and endocardial cushion
3- foramen secundum- septum primum starts to descend- 2 foramen
4- septum secundum- forms the the right of septum primum -- foramen primum disappears
5- septum primum starts to degrade, septum secundum grows-- foramen ovale
6- septum primum and secundum fuse , foramen ovale closes


Function of the foramen ovale before and after birth?

Before birth:
-allows blood flow from right to left
-prevents reflow of blood
After birth:
-closes: shift in pressure to left atrium
-increased pulmonary blood flow


Partitioning of the ventricles

1- muscular ventricular septum forms which causes the inter ventricular foramen to open
2-The aorticopulmonary septum rotates and fuses with the muscular ventricular septum- this closes the inter ventricular foramen and opens the membranous foramen
4-endocardinal cushion grows and separates the atria and ventricles


formation of the aortic and pulmonary trunk

week 5
-mesenchymal cells in wall of bulbus cordis and trunchus anteriorus proliferate
-Bulbur ridges and trunchal ridges
-180 spiralling to form aorticopulmonary septum
-divides the bulbus cordis and the trunchus anterior to form the aortic and pulmonary trunk


Formation of the pericardium

-From the intra-embryonic coelum
-somatic mesoderm forms the parietal pericardium and the fibrous pericardium
-splanchnic mesoderm forms the visceral pericardium


Electrical conductivity

1-pacemaker cells in atrium and sinus venosum
2- SA node in week 5
3- Atrioventricular node and bundle of his: from AV canals and sinus venosum


Summary of what becomes what

Aortic sac- aortic branches
Bulbus cordis- right ventricle
primitive ventricle- left ventricle
primitive atrium- part of left/right atrium
sinus venous- S.V.C and right atrium


How does the foramen ovale close

When baby is born they take a deep breath in
This increases the pressure in the left atrium so it becomes greater than the right atrium
This pushes the septum primum against the septum secundum and causes them to fuse


why does the foramen ovale sometimes not close?

Too much reabsorption of the septum primum
Not enough growth of the septum secundum


Why is the CVS the first major system to develop?

Diffusion alone is not enough to allow nutrition of the embryo


What are the 4 main stages of heart development

1-primitive heart tube
2-heart looping
3-atrial/ventral septation
4-outflow tract septation


When does the inter ventricular foramen close?

end of week 7