Heart Development Flashcards
About how often do congenital cardiac anomalies occur?
How many are severe?
5:1000 to 8:1000 live births
1/3 are severe
What is the order of foramen in atrium septation?
foramen primum at 33 days –> foramen secudum 6th week –> foramen ovale 7th week
What happens during lateral folding?
endocardial heart tubes approach each other and fuse
What are the left and right portions of the incorporated bulbus cordis?
right = conus arteriosus (infundibulum left = aortic vestibule
What occurs in primitive heart folding?
bulbus cordis and ventricles grow quickly –> go anterior and inferior –> atrium and sinus venosus fold up and come to lie dorsally
How do you correct transposition of the great vessels?
put on prostaglandins to keep septal defect open until surgery
What is a transitional AV septal defect?
large primum defect
cleft mitral valve
VSD
When does the fetal heart first beat?
4th week (22 days)
What are the 4 main primitive divisions of the heart?
truncus arteriosus = outflow tube
bulbus cordis
primitive ventricle
primitive atrium
What is the transverse pericardial sinus?
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
Where are right and left bulbar ridges?
more inferior –> R and L bulbar ridgesend up fusing w/ endocardial cusion to form the interventricular septum and aorticopulmonary septum
What do you normally see before and after indomethacin therapy for PDA?
enlarged heart and opacificed lungs –> treatment –> clear lungs and heart smaller
What are the endocardial/ AV cushions?
When do they form?
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
Where is the truncus arteriosus?
ridges are more superior = outflow tract
In general, are atrial septal defects cyanotic or acyanotic?
acyanotic
What are defects in the interventricular septum due to?
membranous part of the septum
What is dextrocardia?
heart folds the exact opposite –> mirror image forms
What is patent ductus arteriosus?
ductus arteriosus is still open = L to R shunt pushing blood from aorta into pulmonary A = acyanotic
can cause pulmonary HTN if untreated
What foramen arise due to the septum primum?
foramen primum
foramen secundum
What are bulbus cordis and truncus arteriosus derived from?
neural crest cells
What type of heart defects are cyanotic?
right to left shunt
What is truncus arteriosus communis?
one great vessel = cyanotic defect
NC migration screwed up –> truncal ridges don’t form correctly
What genes/molecules regulate neural crest migration to the heart?
retinoic acid (vit A)
hox genes
Nf-1
pax 3
What is the aorticopulmonary septum?
divides bulbus cordis and truncus arteriosus into ascending aorta and pulmonary trunk –> fuses w/ endocardial cushion
What type of heart defects are acyanotic?
no shunt or L to R shunt
What does the smooth muscle of the atria arise from?
the sinus venosus
What is transposition of the great vessels?
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
What are the heart fields developed from?
splanchnic mesoderm
established in cranial end of embryo
What happens in primum ASD?
septum primum doesn’t fuse w/ endocardial cushions
associated with mitral valve cleft
How does the bulbar and truncal ridge twisting orient the pulmonary trunk and aorta?
aorta starts anterior –> twist –> posterior at the end
What are angioblastic cords?
masses of splanchnic mesoderm that are the early heart tubes
When does the foramen primum disappear?
when it fuses with endocardial cushions in 6th week
What are the signs of critical aortic stenosis?
Is it cyanotic?
tachypnea, poor feeding and perfusion, may lead to hypoplastic L heart syndrome
yes - is cyanotic bc decreased systemic blood flow
Why can’t pregnant mothers not take accutane?
it is a Vit A derivative –> stops neural crest cells from migrating to the heart –> fetal heart defects
What is hypoplastic left heart syndrome?
mitral valve stenosis or atresia L ventricle hypoplasia aortic valve stenosis or aortic arch hypoplasia cyanotic! 50% die
When does circulation begin?
4th week
What type of pediatric patients are likely to have AV septal defects?
Down’s syndrome = 20% have it
What signal is required for remodeling of AV cushions?
retinoic acid
What is a partial AV septal defect?
primum ASD
single AV valve annulus w/ 2 separate valve orifices
(anterior leaflet of mitral valve is typically cleft)
What type of heart defects cause no shunt?
anomalies of aortic arches
coarctation of aorta
when do the semilunar valves start to develop?
once partition of truncus arteriosus is nearly complete –> valves swell btw bulbus cordis and truncus arteriosus –> blood pressure erodes tissue to cusps
What do the endocardium, myocardium, and epicardium all arise from?
splanchnic mesoderm
What is the clinical presentation of patent ductus arteriosus?
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
What are AV septal defects caused by?
are they cyanotic or acyanotic?
failure of endocardial cushions to fuse
acyanotic
What is a mesentery?
double layer of splanchnic mesoderm = route for nerves and vessels to get to organs
Are ventricular septal defects acyanotic of cyanotic?
What is the basis for the defect?
acyanotic
interventricular septum never fuses w/ endocardial cushions
Why doesn’t patent ductus arteriosus close?
How do you treat it?
low oxygen content
circulating prostaglandin E2 = vasodilator that keeps duct open; mediated by COX-2
treatment = COX-2 inhibitors (ibuprofen, indomethacin)
What is the dorsal mesocardium?
bridge of mesoderm that connects the developing heart to the posterior wall of the embryo
What do secondary heart fields develop into?
right ventricle
outflow tract
part of atria (venous pole)
What is tetralogy of fallot?
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
How do neural crest cells contribute to heart development?
originate from myelencephalon –> migrate through pharyngeal arches 3, 4, and 6 –> help form truncus arteriosus and aorticopulmonary septa
Aortic or pulmonary valve defects can be due to disruption of what embryonic tissue?
neural crest (migration)
How does ventricular septation occur?
interventricular septum grows superiorly to eventually fuse with the endocardial cushions
(still have interventricular foramen for most of development)
What is the ductus arteriosus?
connection btw pulmonary artery and aorta in utero that should close when born
shunts blood from pulmonary A straight to aorta, I think
What does the left horn of the sinus venosus give rise to?
orifice of the coronary sinus
What happens in secundum ASD?
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
What does the right horn of the sinus venosus give rise to?
orifices of superior and inferior vena cava
sinus venarum
What happens to the left and right sinuatrial valves?
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
Which direction does the bulboventricular loop bend?
to the right
What are the 2 types of atrial septal defects?
secundum ASD
primum ASD
What is the heart derived from?
splanchnic mesoderm
mesenchyme
angioblastic tissue
What do primary heart fields develop into?
left and right atria and the left ventricle
What is critical pulmonary stenosis?
cusps of pulmonary valves are fused or thickened
cyanotic if called “critical”
What is a complete AV septal defect?
primum ASD and VSD w/ a common AV valve
Where are the septum primum and secundum, from R to L?
R = secundum L = primum
What is double outlet right ventricle?
cyanotic defect
both great vessels lead to R ventricle
ventricular septal defect usually
caused by abnormal migration of bulbar ridges
When do the endocardial tubes begin to fuse/ when are they fully fused?
begin at day 21
finished at 22 days
What does heart folding begin to occur?
day 23
When is heart folding complete?
day 35
