cardiovascular embryology

Question 1

name the three cardiac cell progenitors

Answer 1

• primary and secondary heart field (known collectively as the cardiac crescent)
• cardiac neural crest cells

Question 2

where is the cardiac crescent found?

Answer 2

cranial end of trilaminar embryo on mesoderm layer (lateral plate mesoderm)

Question 3

when does the cardiac crescent develop?

Answer 3

day 15-16

Question 4

what do the PHF form?

Answer 4

heart tube (main structures of the heart) - around 22 days

• L ventricle and most of the 2 artia

Question 5

what do the SHF do?

Answer 5

add to heart - R ventricle and little of the atria

Question 6

what do the CNCCs do?

Answer 6

migrate from neural tube to heart tube, contributing to septa and vessels

Question 7

what happens simultaneously with heart tube development?

Answer 7

embryonic folding, resulting in the developing heart being located in the ventral part of the now 3D embryo

Question 8

what does the notochord do?

Answer 8

tell mesoderm to differentiate into lateral plate mesoderm

Question 9

when do NCC arise?

Answer 9

day 18-19

Question 10

label this diagram of the blind-ended heart tube on day 20 and describe what happens during its formation

Answer 10

• heart tube arises from cardiac crescent mesoderm
• simulatenously, the surrounding lateral plate mesoderm and intraembronic coelom (body cavity) form the pericardial membrane and pericardial cavity respectively
• the pericardium continues to surround the heart in the adult

Question 11

label this diagram of the differentiated heart tube on day 20

Answer 11

Question 12

label this diagram of the structures formed during further differentiation of the heart on day 21

Answer 12

Question 13

when does folding of the heart occur?

Answer 13

day 21 - 35

Question 14

how do SHF progenitor cells contribute to development of the heart tube?

Answer 14

inflow and outflow regions of developing heart tube

Question 15

how can defects in CNCC cells cause genetic defects?

Answer 15

defects can cause them to not migrate and adhere properly to the heart, meaning certain structures won’t be developed properly

Question 16

define foramen ovale

Answer 16

foetal cardiac shunt in the foetal atrial septum that permits blood to flow from the sinus venosus and right atrium to the left atrium

Question 17

what happens to the foramen ovale at birth?

Answer 17

closes and forms the fossa ovalis in the walls of the right and left atria

Question 18

how can the failure to close foramen ovale at birth causes CHD?

Answer 18

an atrial septal defect (ASD) termed patent foramen ovale (PFO), which permits the mixing of high oxygen blood in the left atrium and low oxygen blood in the right atrium

Question 19

define ductus arteriosus

Answer 19

a foetal cardiac shunt that permits blood to flow from the foetal pulmonary artery to the aorta, thereby bypassing the foetal lungs

Question 20

what happens to the ductus arteriosus?

Answer 20

closes and forms the ligamentum arteriosum, an embryonic remnant ligament between the pulmonary trunk and aorta

Question 21

what happens if the ductus arterious fails to close at birth?

Answer 21

can result in an patent ductus arteriosus (PDA), which permits the mixing of high oxygen blood in the aorta and low oxygen blood in the pulmonary trunk

Question 22

define septa

Answer 22

partition between chambers

Question 23

name the different septa and where they originate from

Answer 23

• atrioventricular septum (mesoderm)
• atrial septum (mesoderm)
• ventricular septum (mesoderm and neural) - membranous (neural crest) and muscular (mesoderm)
• aorticopulmonary septum (neural crest)

Question 24

label this diagram with the adult cardiac septa

Answer 24

A = atrial septum

B = av septum

C = ventricular septum

Question 25

label this diagram with the adult cardiac septa

Answer 25

a = aorticopulmonary septum

b = membranous ventricular septum

c = muscular ventricular septum

Question 26

label this diagram of the atrioventirulcar septum

Answer 26

A = fusion of endocardial cushions

B = AV canals

C = common artia

D = common ventircle and outflow tract

Question 27

label this diagram of the atrial septum

Answer 27

a = AV septum

b = secondary atrial septum

c = primary atrial septum

d = foramen ovale

Question 28

when does the AV septum form?

Answer 28

around 28 days/4 weeks

Question 29

when do the ventricular septum and aorticopulmonary septum form?

Answer 29

around 5 weeks

Question 30

what does the aorticopulmonary septum separate?

Answer 30

aorta and pulmonary trunk

Question 31

when does the atrial septum form?

Answer 31

around 5 weeks

Question 32

how are CHDs patent foramen ovale and patent ductus arteriosus caused?

Answer 32

when foetal cardiac shunts fail to close at birth

Question 33

how can neural crest abnormalities cause CHDs?

Answer 33

Neural crest abnormalities can lead to impaired cell migration and adhesion. This can disrupt the development of the cardiac structures to which the CNCCs contribute.

Question 34

how are VSDs caused?

Answer 34

neural crest defects can cause the membranous ventricular and aorticopulmonary septum to be ‘shifted’ to the right

can cause a VSD, meaning blood from right and left ventricles can mix

Question 35

what are the 4 features of tetralogy or fallot CHD?

Answer 35

• Pulmonary stenosis
• Over-riding aorta
• Right ventricular hypertrophy
• VSD

Question 36

what causes Tetraology of Fallot?

Answer 36

cardiac neural crest cell abnormality

Question 37

what is a patent ductus arteriosus?

Answer 37

when the foetal cardiac shunt between the pulmonary trunk and descending aorta doesn’t close at birth

Question 38

label this image of the features of Tetralogy of Fallot

Answer 38

A: Pulmonary artery stenosis

B: Pulmonary valve stenosis

C: Over-riding aorta

D: Ventricular septal defect

E: Right ventricular hypertrophy. Growth of the right ventricular myocardium occurs due to the work required to pump blood via both pulmonary trunk and aorta.

F: Patent ductus arteriosus. The ductus arterious is a foetal cardiac shunt between the pulmonary trunk and descending aorta. This channel should close at birth to form the ligamentum arteriosum but remains patent in this abnormality.