Cardiac Embryology

Question 1

The primitive heart consist of what parts?

Answer 1

Truncus arteriosus 
Bulbus cordis
ventricle
atria
sinus venosus

Question 2

What parts of the primitive heart becomes which parts in developed heart?

Answer 2

Truncus arteriosus --> aorta and PA
Bulbus cordis --> smooth RV and LV
ventricle --> trabeculated LV/RV
atria --> trabeculated RA/LA
sinus venosus --> RA smooth [sinus veranum] (right horn), coronary sinus (left horn)

Question 3

Where do neural crest cells migrate?

Answer 3

to truncal-bulbar ridge –> forms aorta and PA

Question 4

What happens if the neural crest cells fail to migrate?

Answer 4

Transposition of the great vessels (failure to spiral)
Tetralogy of Falot (Skewed AP septum development)
Persistent truncus arteriosus (partial AP septum development)

Question 5

Describe the steps in ventricular septum formation:

Answer 5

1) aorticopulmonary septum forms (eventually will devide the LVOT and RVOT)
2) muscular ventricular septum forms
3) Membranous septum forms on top; AP twists
4) Endocardial cushions arise –> separate R/L atrium and ventricles

Question 6

Which syndrome is related to endcardial defects?

Answer 6

Down syndrome

Question 7

What some pathologies with ventricular septum malformation?

Answer 7

ASD and VSD (higher risj with endocardial cushion defects)

Question 8

Which structure grows superiorly of the endocardial cushion in atrial septum formatoon?

Answer 8

Septum prinum

Question 9

What happens when the septum prinum divides and one part regresses?

Answer 9

foramen secundum develops (a hole) and foramen primum –> leads to ASDs if persists in adulthood

Question 10

List the steps of atrial septum formation after the septum prinum and endocardial cushion fuse:

Answer 10

1) foramen secondum still present
2) septum secundum develops right to the septum prinum (covers the foramen secondum) BUT a foramen ovale forms that lets blood from RA to LA
3) postnatally the LA pressure increases and the structure formed from endocardial cushion+septum prinum is pushed and fuses with the septum secundum —> foramen ovale closed

Question 11

Why is the RA pressure high in fetus?

Answer 11

PA have really high resistance

Question 12

HOw does the fetus receive oxygenated blood?

Answer 12

from umbilical cord

Question 13

Where does the umbilical blood go?

Answer 13

to RA (bypasses liver via ductus venosus IMP)

Question 14

How does the blood bypass the pulmonary circulation?

Answer 14

Blood travels through the foramen ovale

Question 15

T or F: in the fetus some blood can go directly to RV via SVC

Answer 15

T

Question 16

How does blood from RV circulate in a fetus?

Answer 16

Ductus arteriosa connects PA to aorta, and blood drains through here

Question 17

When the foramen ovale closes what is called?

Answer 17

Fossa ovalis

Question 18

What maintains the DA open?

Answer 18

low O2, and high prstaglandins

Question 19

What structures form the SVC/IVC?

Answer 19

cardinal veins:
R common cardinal vein and R anterior cardinal vein –> SVC
Posterior veins –> IVC

Question 20

What is cardiac looping?

Answer 20

heart tube loops at 4 weeks of gestation and establishes left-right orientation in chest

Question 21

What things is required for cardiac looping?

Answer 21

Cilia and dynein

Question 22

The endocardial cushions contribute to which structures?

Answer 22

• atrial septum
• ventricular septum
• AV valves
• semilunar valves

Question 23

What is a patent foramen ovale?

Answer 23

when septum prinum and secondum fal to fuse found on 25%

Question 24

When does the cardiac development start?

Answer 24

3 weeks

Question 25

Which two layers start the development?

Answer 25

Epiblast (dorsal) –> later ectoderm

Hypoblast (ventral) –> later endoderm

Question 26

Where does the primitive streak begin?

Answer 26

epiblast

Question 27

Which layer gives the heart?

Answer 27

Mesoderm (visceral)

Question 28

What happens at the embryo’s head?

Answer 28

Results to the primary heart field (horseshoe shape with two limbs)

Question 29

What does the endoderm layer do at the primary heart field?

Answer 29

Secretes vascular endothelial growth factor (VEGF)

Question 30

Whats the function of VEGF?

Answer 30

signals cells in the limbs to organize intwo two heart tubes

Question 31

T or F: the limbs have two pericardial cavity

Answer 31

T

Question 32

What does the inferior pericardial CAVITY CONNECT TO?

Answer 32

Vitelline vein from yolk sac

Question 33

Where does the blood from vitelline vein exit?

Answer 33

via dorsal aorta

Question 34

What is the lateral folding?

Answer 34

flat embryo to cylindrical shape –> the two heart tubes fuse anteriorly –> primitive heart tube

Question 35

What happens to the vitelline veins when the two heart tubes fuse?

Answer 35

They fuse to become the sinus venosus (inflow tract to heart tube)

Question 36

What happens to the two dorsal aorta when the two tubes fuse?

Answer 36

BEcomes the aortic sac (ie. outflow tract)

Question 37

How does the dorsal mesocardium appeare?

Answer 37

Fusing of the pericardial cavities that then elongate at the midline and hangs and has a cavity
- the inner cells of the cavity –> endocardium
the outer cells –> cardiac myoblasts –> myocardium

Question 38

Where does the initial electric discharge come from?

Answer 38

sinus venosus

Question 39

What folding causes the heart to go down the chest?

Answer 39

craniocaudal folding at week 4

Question 40

What gives rise to the epicardium?

Answer 40

visceral pericardium

Question 41

T or F: the aortic arches stay intact in adulthood

Answer 41

F:
Aortic arch V regresses
I becomes the maxillary artery
II becomes the stapedial
III gives rise to common carotids (and part of internal carotid)
Left IV becomes the aortic arch, right IV become right subclavian artery
VI becomes the PA (and left become ductus arteriosus)