Embryology

Question 1

What happens in week 3

Answer 1

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

Question 2

What is part of the primordial cardiovascular system?

Answer 2

1- Trunchus anterior
2-Bulbus Cordis
3-Atrium 
4-Ventricle
5-Sinus Venosum

Question 3

What is the Trunchus anterior?

Answer 3

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

Question 4

What is the sinus venosum?

Answer 4

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

Question 5

What is the bulbogenic loop?

Answer 5

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

Question 6

Partitioning

Answer 6

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

Question 7

Partitioning of the atria

Answer 7

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

Question 8

Function of the foramen ovale before and after birth?

Answer 8

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

Question 9

Partitioning of the ventricles

Answer 9

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

Question 10

formation of the aortic and pulmonary trunk

Answer 10

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

Question 11

Formation of the pericardium

Answer 11

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

Question 12

Electrical conductivity

Answer 12

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

Question 13

Summary of what becomes what

Answer 13

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

Question 14

How does the foramen ovale close

Answer 14

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

Question 15

why does the foramen ovale sometimes not close?

Answer 15

Too much reabsorption of the septum primum

Not enough growth of the septum secundum

Question 16

Why is the CVS the first major system to develop?

Answer 16

Diffusion alone is not enough to allow nutrition of the embryo

Question 17

What are the 4 main stages of heart development

Answer 17

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

Question 18

When does the inter ventricular foramen close?

Answer 18

end of week 7