Heart Development

Question 1

About how often do congenital cardiac anomalies occur?

How many are severe?

Answer 1

5:1000 to 8:1000 live births

1/3 are severe

Question 2

What is the order of foramen in atrium septation?

Answer 2

foramen primum at 33 days –> foramen secudum 6th week –> foramen ovale 7th week

Question 3

What happens during lateral folding?

Answer 3

endocardial heart tubes approach each other and fuse

Question 4

What are the left and right portions of the incorporated bulbus cordis?

Answer 4

right = conus arteriosus (infundibulum
left = aortic vestibule

Question 5

What occurs in primitive heart folding?

Answer 5

bulbus cordis and ventricles grow quickly –> go anterior and inferior –> atrium and sinus venosus fold up and come to lie dorsally

Question 6

How do you correct transposition of the great vessels?

Answer 6

put on prostaglandins to keep septal defect open until surgery

Question 7

What is a transitional AV septal defect?

Answer 7

large primum defect
cleft mitral valve
VSD

Question 8

When does the fetal heart first beat?

Answer 8

4th week (22 days)

Question 9

What are the 4 main primitive divisions of the heart?

Answer 9

truncus arteriosus = outflow tube
bulbus cordis
primitive ventricle
primitive atrium

Question 10

What is the transverse pericardial sinus?

Answer 10

in embryo - where dorsal mesocardium once was between the heart and the posterior body wall
In an adult - btw the aorta and pulmonary artery; put fingers through to clamp aorta

Question 11

Where are right and left bulbar ridges?

Answer 11

more inferior –> R and L bulbar ridgesend up fusing w/ endocardial cusion to form the interventricular septum and aorticopulmonary septum

Question 12

What do you normally see before and after indomethacin therapy for PDA?

Answer 12

enlarged heart and opacificed lungs –> treatment –> clear lungs and heart smaller

Question 13

What are the endocardial/ AV cushions?

When do they form?

Answer 13

derived from mesoderm from dorsal and ventral walls –> grow together –> right and left AV canals and separates atria from ventricle
mesenchyme invades in 5th week

Question 14

Where is the truncus arteriosus?

Answer 14

ridges are more superior = outflow tract

Question 15

In general, are atrial septal defects cyanotic or acyanotic?

Answer 15

acyanotic

Question 16

What are defects in the interventricular septum due to?

Answer 16

membranous part of the septum

Question 17

What is dextrocardia?

Answer 17

heart folds the exact opposite –> mirror image forms

Question 18

What is patent ductus arteriosus?

Answer 18

ductus arteriosus is still open = L to R shunt pushing blood from aorta into pulmonary A = acyanotic
can cause pulmonary HTN if untreated

Question 19

What foramen arise due to the septum primum?

Answer 19

foramen primum

foramen secundum

Question 20

What are bulbus cordis and truncus arteriosus derived from?

Answer 20

neural crest cells

Question 21

What type of heart defects are cyanotic?

Answer 21

right to left shunt

Question 22

What is truncus arteriosus communis?

Answer 22

one great vessel = cyanotic defect

NC migration screwed up –> truncal ridges don’t form correctly

Question 23

What genes/molecules regulate neural crest migration to the heart?

Answer 23

retinoic acid (vit A)
hox genes
Nf-1
pax 3

Question 24

What is the aorticopulmonary septum?

Answer 24

divides bulbus cordis and truncus arteriosus into ascending aorta and pulmonary trunk –> fuses w/ endocardial cushion

Question 25

What type of heart defects are acyanotic?

Answer 25

no shunt or L to R shunt

Question 26

What does the smooth muscle of the atria arise from?

Answer 26

the sinus venosus

Question 27

What is transposition of the great vessels?

Answer 27

R ventricle now goes to aorta and L ventricle now goes to pulmonary trunk; also have septal defect acyanotic caused by NC cells that don't migrate properly --> bulbar and truncal folds dont' twist right

Question 28

What are the heart fields developed from?

Answer 28

splanchnic mesoderm | established in cranial end of embryo

Question 29

What happens in primum ASD?

Answer 29

septum primum doesn't fuse w/ endocardial cushions | associated with mitral valve cleft

Question 30

How does the bulbar and truncal ridge twisting orient the pulmonary trunk and aorta?

Answer 30

aorta starts anterior --> twist --> posterior at the end

Question 31

What are angioblastic cords?

Answer 31

masses of splanchnic mesoderm that are the early heart tubes

Question 32

When does the foramen primum disappear?

Answer 32

when it fuses with endocardial cushions in 6th week

Question 33

What are the signs of critical aortic stenosis? | Is it cyanotic?

Answer 33

tachypnea, poor feeding and perfusion, may lead to hypoplastic L heart syndrome yes - is cyanotic bc decreased systemic blood flow

Question 34

Why can't pregnant mothers not take accutane?

Answer 34

it is a Vit A derivative --> stops neural crest cells from migrating to the heart --> fetal heart defects

Question 35

What is hypoplastic left heart syndrome?

Answer 35

``` mitral valve stenosis or atresia L ventricle hypoplasia aortic valve stenosis or aortic arch hypoplasia cyanotic! 50% die ```

Question 36

When does circulation begin?

Answer 36

4th week

Question 37

What type of pediatric patients are likely to have AV septal defects?

Answer 37

Down's syndrome = 20% have it

Question 38

What signal is required for remodeling of AV cushions?

Answer 38

retinoic acid

Question 39

What is a partial AV septal defect?

Answer 39

primum ASD single AV valve annulus w/ 2 separate valve orifices (anterior leaflet of mitral valve is typically cleft)

Question 40

What type of heart defects cause no shunt?

Answer 40

anomalies of aortic arches | coarctation of aorta

Question 41

when do the semilunar valves start to develop?

Answer 41

once partition of truncus arteriosus is nearly complete --> valves swell btw bulbus cordis and truncus arteriosus --> blood pressure erodes tissue to cusps

Question 42

What do the endocardium, myocardium, and epicardium all arise from?

Answer 42

splanchnic mesoderm

Question 43

What is the clinical presentation of patent ductus arteriosus?

Answer 43

continuous murmor large defect = poor eating, sweating w/ crying or eating, rapid heart rate, tachypnea persistent: high pressure blood from aorta can destroy capillary beds in lungs

Question 44

What are AV septal defects caused by? | are they cyanotic or acyanotic?

Answer 44

failure of endocardial cushions to fuse | acyanotic

Question 45

What is a mesentery?

Answer 45

double layer of splanchnic mesoderm = route for nerves and vessels to get to organs

Question 46

Are ventricular septal defects acyanotic of cyanotic? | What is the basis for the defect?

Answer 46

acyanotic | interventricular septum never fuses w/ endocardial cushions

Question 47

Why doesn't patent ductus arteriosus close? | How do you treat it?

Answer 47

low oxygen content circulating prostaglandin E2 = vasodilator that keeps duct open; mediated by COX-2 treatment = COX-2 inhibitors (ibuprofen, indomethacin)

Question 48

What is the dorsal mesocardium?

Answer 48

bridge of mesoderm that connects the developing heart to the posterior wall of the embryo

Question 49

What do secondary heart fields develop into?

Answer 49

right ventricle outflow tract part of atria (venous pole)

Question 50

What is tetralogy of fallot?

Answer 50

common and serios defect polmonary stenosis and interventricular septal defect --> over-riding aorta and R ventricle hypertrophy cyanotic caused by abnormal NC septation of outflow tract

Question 51

How do neural crest cells contribute to heart development?

Answer 51

originate from myelencephalon --> migrate through pharyngeal arches 3, 4, and 6 --> help form truncus arteriosus and aorticopulmonary septa

Question 52

Aortic or pulmonary valve defects can be due to disruption of what embryonic tissue?

Answer 52

neural crest (migration)

Question 53

How does ventricular septation occur?

Answer 53

interventricular septum grows superiorly to eventually fuse with the endocardial cushions (still have interventricular foramen for most of development)

Question 54

What is the ductus arteriosus?

Answer 54

connection btw pulmonary artery and aorta in utero that should close when born shunts blood from pulmonary A straight to aorta, I think

Question 55

What does the left horn of the sinus venosus give rise to?

Answer 55

orifice of the coronary sinus

Question 56

What happens in secundum ASD?

Answer 56

patent foramen ovale - most common type = incomplete adhesion of foramen ovale and septum secundum aftern birth could also have inadequate dev of septum secundum; excessive cell death

Question 57

What does the right horn of the sinus venosus give rise to?

Answer 57

orifices of superior and inferior vena cava | sinus venarum

Question 58

What happens to the left and right sinuatrial valves?

Answer 58

cranially: both meet and fuse w/ septum spurium right cranial --> crista terminalis right caudal --> valve of coronary sinus and most of valve of inferior vena cava

Question 59

Which direction does the bulboventricular loop bend?

Answer 59

to the right

Question 60

What are the 2 types of atrial septal defects?

Answer 60

secundum ASD | primum ASD

Question 61

What is the heart derived from?

Answer 61

splanchnic mesoderm mesenchyme angioblastic tissue

Question 62

What do primary heart fields develop into?

Answer 62

left and right atria and the left ventricle

Question 63

What is critical pulmonary stenosis?

Answer 63

cusps of pulmonary valves are fused or thickened | cyanotic if called "critical"

Question 64

What is a complete AV septal defect?

Answer 64

primum ASD and VSD w/ a common AV valve

Question 65

Where are the septum primum and secundum, from R to L?

Answer 65

``` R = secundum L = primum ```

Question 66

What is double outlet right ventricle?

Answer 66

cyanotic defect both great vessels lead to R ventricle ventricular septal defect usually caused by abnormal migration of bulbar ridges

Question 67

When do the endocardial tubes begin to fuse/ when are they fully fused?

Answer 67

begin at day 21 | finished at 22 days

Question 68

What does heart folding begin to occur?

Answer 68

day 23

Question 69

When is heart folding complete?

Answer 69

day 35