Cardiac Embryology

Question 1

characteristics of adult heart

Answer 1

one-way pump
blood does NOT flow backwards
separated oxygenated and deoxygenated blood

Question 2

characteristics of fetal heart

Answer 2

two deviations to bypass pulmonary circulation
mixed oxygenated and deoxygenated blood

Question 3

why do fetal hearts bypass pulmonary circulation

Answer 3

lungs in fetus are flat - no gas exchange occurs because fetus is surrounded by amniotic fluid

Question 4

foramen ovale

Answer 4

opening/flap from right to left atrium

allows blood to bypass pulmonary circulation

Question 5

what does the foramen ovale become after birth

Answer 5

fossa ovale

Question 6

ductus arteriosus

Answer 6

opening from the aorta into the pulmonary trunk

shunts blood directly into systemic circulation instead of pulmonary

Question 7

what does the ductus arteriosus become after birth

Answer 7

ligamentum arteriosum

Question 8

general steps of cardiac embryology

Answer 8

1. endocardial tubes form and fuse into primary heart tube
2. primary heart tube forms bulges and indentations
3. primary atrium folds on top of itself to get to the top (cardiac loop)
4. truncus arteriosus and aortic sac form as the outlet
5. septum primum extends down down septum intermedium but leaves an opening
6. septum intermedium extends up toward septum primum
7. endocardial cushions project to separate atrium and ventricles
8. septum second forms next to septum primum and extends toward septum intermedium
9. septa leave a flap between right and left atria (foramen ovale)
10. interventricular septum grows upward to separate ventricles

Question 9

what two bulges form first

Answer 9

top: bulbus cordis (BC)
bottom: primitive ventricle (PV)

Question 10

what indentations form first

Answer 10

bulboventricular sinus (separates BC and PV)

atrioventricular sinus (separates PV and PA)

Question 11

when does the primitive atrium form

Answer 11

forms from the indentation of the AV sinus

below the primary ventricle

Question 12

what does the primitive atrium become in adults

Answer 12

auricles

Question 13

cardiac loop

Answer 13

S shaped fold

blood flows from bottom to top

Question 14

sinus venosus

Answer 14

entry point of blood into the primitive atrium

flow up the cardiac loop to the BC

Question 15

what does the sinus venosus become in adults

Answer 15

cranial and caudal vena cava

Question 16

truncus arteriosus

Answer 16

dilation above the bulbus cordis

gives rise to the aorta and pulmonary artery

Question 17

conotruncal ridges

Answer 17

tissue inside the truncus arteriosus that separates the aorta and pulmonary trunk

Question 18

aortic sac

Answer 18

dilation above the truncus arteriosus

gives rise to the aortic roots

Question 19

aortic roots

Answer 19

forms the aortic arch and brachiocephalic trunk

Question 20

septum primum

Answer 20

located on top of the atrium

separates R and L atrium but does not fully close in fetus in order to maintain blood flow between atria

Question 21

ostium primum

Answer 21

opening between septum primum and ventricle to maintain blood flow between R and L atria

Question 22

septum intermedium

Answer 22

located in the center between both ventricles and atria

grows upwards to separate the R and L atrium but forms fenestrations to maintain blood flow

Question 23

ostium secundum

Answer 23

openings formed by fenestrations between the septum primum and intermedium

Question 24

endocardial cushions

Answer 24

projections from the septum that grow sideways to separate atria and ventricles

does not fully attach to septum intermedium to maintain AV canals

Question 25

AV canals

Answer 25

openings formed between both atria and ventricles

becomes the L and R AV valves

Question 26

how does the foramen ovale become the fossa ovale

Answer 26

foramen forms a flap between the L and R atria that responds to changes in pressure

atria becomes low pressure at birth –> causes flaps to close and foramen ovale to fuse to surrounding tissue

Question 27

cardiovascular malformations in dogs

Answer 27

1. patent ductus arteriosus
2. pulmonary stenosis
3. aortic stenosis

Question 28

patent ductus arteriosus (PDA)

Answer 28

failure of the ductus arteriosus to close, leaving an opening between the pulmonary trunk and the aorta

blood flows from aorta –> pulmonary trunk

Question 29

cardiovascular malformations in cats

Answer 29

1. atrial or ventricular septal defects
2. AV valve dysplasia

Question 30

atrial/ventricular septal defects

Answer 30

malformations in the divisions between atria and ventricles

causes openings between the chambers

Question 31

AV valve dysplasia

Answer 31

malformation of the AV valves causing regurgitation of blood

Question 32

tetralogy of fallot

Answer 32

combination of 4 congenital heart defects
1. pulmonary stenosis
2. ventricular septal defect
3. overriding aorta
4. hypertrophic right ventricle

Question 33

what causes pulmonary stenosis

Answer 33

conotruncal ridges do not come down symmetrically; causes a narrowing of the lumen of the pulmonary trunk

Question 34

what causes ventricular septal defect

Answer 34

paraconal ridges do not come down and fuse with the muscular interventricular ridge; causes an opening between right and left ventricles

Question 35

what causes overriding aorta

Answer 35

paraconal ridges come down asymmetrically; causes aorta to be too large and located on top of the interventricular septum

Question 36

what causes hypertrophic right ventricle

Answer 36

blood getting shunted through the ventricular septal defect causes right ventricle to need to pump harder than normal to get blood into the pulmonary trunk