11.22 B Flashcards
What are the endocardial tubes?
lines of embryonic heart precursor cells that will give rsie to the primitive heart tube
The medial endocardial tubes give rise to what?
the dorsal aortae
The lateral endocardial tubes give rise to what?
venous structures
Cranial folding on day 20 gives rise to what embryonic heart changes?
- formation of the aortic arch
- fusion of the right and left endocardial tubes
Describe the sequence of blood flow through the primitive heart tube.
sinus venosus to atrium to ventricle to bulbus cordis to aortic sac
When does the embryonic heart start to beat?
it starts beating on day 22 but with little directionality
What is the truncus arteriosus?
the part of the primitive heart tube that will give rise to the ascending aorta and pulmonary trunk
What is the sinus venosus?
the primitive heart structure that gives rise to the right atrium and coronary sinus
What events give rise to the pericardial sinuses?
folding of the primitive heart tube
What is cardiac jelly?
ECM secreted in between myocardium and primitive endothelium of the heart tube
The pericardial sac forms from what embryonic cell population?
mesothelial cells
From inside out, what are the four layers of the heart tube?
- endocardium (primitive endothelium)
- cardiac jelly (ECM)
- myocardium
- epicardium (visceral pericardium)
During folding of the heart tube, the bulbus cordis is displaced in which direction?
inferiorly, ventrally, and to the right side of the body
Duringn folding of the heart tube, the sinus venosus is displaced in which direction?
superiorly and posteriorly
What is dextrocardia?
improper twisting of the heart tube such that the base of the heart is directed to the right side of the body
What is the difference in prognosis between those with dextrocardia and those with situs inversus?
those with just dextrocardia are more likely to have additional heart defects while those with situs inversus only have a slightly increased risk
Endocardial cushions form what?
the septum intermedium which separates the atrium from ventricles
What is the septum intermedium?
the structure that separates the atrium from the ventricles
What is the septum primum?
a crescent-shaped structure that grows down from the superoposterior wall of the atrium to begin forming the left and right atrium
What is the ostium primum?
the opening in the septum primum between the left and right atrium
What is the ostium secundum?
an opening that forms in the septum primum before closure of the ostium primum to keep the right and left atria connected
Endocardial cushion cells are derived from what?
neural crest cells
Why do individuals that suffer from craniofacial defects often also have congenital heart defects?
because both are due to neural crest cell defects
Neural crest cell deficits often disrupt formation of what heart structures?
endocardial cushions
Endocarial cushion defects can lead to what heart defects?
- atrial and ventricular septal defects
- atrioventricular defects
- transposition of the great vessels
What is an atrioventricular canal?
an atrioventricular septal defect (aka an endocardial cushion defect)
People with Down Syndrome commonly have what heart defect?
an atrioventricular septal defect
How does an atrioventricular septal defect often present?
- tachypnea
- poor feeding (need to breath instead)
- growth retardation
- typically identified around 6 weeks
- cyanosis sometimes seen
What is the foramen ovale?
an opening in the septum secundum
The foramen ovale and ostium secundum allow for what throughout embryonic development?
blood flow from the right to left atrium
A one way intraatrial valve is formed by what structures during embryonic development?
the septum secundum (an its foramen ovale) and the ostium secundum in the septum primum
In adults, an atrial septal defect allows flow of blood in which direction?
left to right atrium
What symptoms are present with an atrial septal defect?
- often very few
- shortness of breath
- easy fatigue
- poor growth
What murmur most often accompanies an atrial septal defect?
an S2 split thanks to delayed pulmonic valve closure due to more blood passing through the right side of the heart
How is an atrial septal defect often treated?
by placing a septal occluder and without open heart surgery
How does a secundum atrial septal defect arise?
poor growth of the septum secundum leaves overlap between the foramen ovale and the ostium secundum
How does a patent foramen ovale develop?
from failure of the two atrial septa to fuse
A patent foramen ovale doesn’t often lead to problems because…
as long as pressure in the left atrium is higher than that of the right, the foramen ovale “valve” is kept shut
A patient presents with fixed splitting of the second heart sound, an ejection murmur, right ventricular conduction delay, and enlargement of the right heart. You suspect what?
an atrial septal defect
Patent foramen ovale are most problematic because they can lead to what?
paradoxical embolization
What is a paradoxical embolization?
an embolus arising in the systemic venous system or right atrium crosses the patent foramen ovale and enters systemic arterial circulation
The smooth walls of the atria are derived from what heart tube structure?
the sinus venosus
What is the interventricular septum?
the divider between the two ventricles
What is the interventricular foramen?
the hole between the two ventricles left by the halted growth of the muscular interventricular septum
The interventricular septum is composed of what two portions?
the muscular and the membranous
How are ventricular septal defects treated?
most close on their own by age 5
What is the truncus arteriosus?
the structure that will give rise to both the aorta and the pulmonic trunk
What are conotruncal swellings?
ridges that develop in the truncus arteriosus wall that will divide it into the aorta and pulmonic trunk
The conotruncal swellings of the truncus arteriosus are derived from what cell population?
neural crest cells
Failure to form the septum of the truncus arteriosus outflow tract leads to what problems?
- transposition of the great arteries
- pulmonary stenosis
- persistent truncus arteriosus
- tetraology of Fallot
How does transposition of the great vessels present?
with cyanosis
Infants with transposition of the great vessels can live longer without treatment if what occurs?
persistent or patent foramen ovale or patent ductus arteriosus
What is the ductus arteriosus?
a vessel connecting the pulmonary artery to the proximal descending aorta
What is persistent truncus arteriosus?
failure of the truncus arteriosus to divide and give rise to the aorta and pulmonary trunk
Persistent truncus arteriosus presents with what?
cyanosis and death unless corrected
What is the tetraology of Fallot?
- ventricular septal defect
- pulmonary stenosis
- aorta that overrides both ventricles
- hypertrophy of right ventricle
When is tetraology of Fallot typically detected?
months to years after birth
How does tetraology often present?
sudden incidence of cyanosis with hyperpnea between 2 mo and 2 yrs old
The severity of Tetraology of Fallot is largely dictated by what factor?
the degree of pulmonary stenosis
How does pulmonary stenosis present?
- usually asymptomatic unless the individual is exercising
- if more severe, there may be a an S2 split
S2 splitting is most often indicative of what?
pulmonary stenosis
Rheumatic disease can sometimes lead to what heart defect?
aortic valve stenosis
Aortic valvular stenosis leads to what secondary problem?
enlargement of the aortic arch
How do chordea tendonae form?
through programmed cell death
What is the ligamentum arteriosum?
the remnants of the ductus arteriosus
What is special about ductus arteriosus smooth muscle?
it is induced to contrcat upon exposure to oxygen
Coarctation of the aorta is due to what?
malpositioning of the ductus arteriosus smooth muscle
Hypertension in the upper extremities and hypotension in the lower is the hallmark of what defect?
coarctation of the heart
How does coarctation of the heart often present?
- upper extremity hypertension and lower extremity hypotension
- left ventricular hypertrophy
- pain upon exercise in lower limbs
Notching of the lower surface of the ribs is indicative of what heart defect?
coarctation of the aorta
The third aortic arch often gives rise to what adult structures?
internal carotid artery
The fourth aortic arch often gives rise to what adult structures?
the right subclavian artery and arch of the aorta
The sixth aortic arch often gives rise to what adult structures?
the pulmonary arteries and ligamentous arteriosus
What is the embryonic importance of the ductus arteriosus?
connect the pulmonary arteries to the arch of the aorta thus bypassing the fetal lungs
The aortic arches are surrounded by what nerves?
the left and right recurrent laryngeal nerve
Name the three arteries that come off the aortic arch?
- brachiocephalic
- left common carotid
- left subclavian
Aortic/branchial arch anomalies often lead to what?
disrupted breathing and problems swallowing
What are the vitelline veins?
those serving the yolk sac
What are the umbilical veins?
those serving the placenta
What are the cardinal veins?
those serving the embryo
What are the three pairs of veins returning blood to the embryonic heart at the sinus venosus?
- vitelline
- umbilical
- cardinal
How does venous return shift during development?
initially, cardinal veins are bilateral with return of teh blood to both horns of teh sinus venosus, but then there is a shift to the right
The superior vena cava is derived from what?
the right anterior cardinal vein
The inferior vena cava is derived from what embryonic structure?
the inferior vitelline vein
The right horn of the sinus venosus becomes what?
part of the right atrium
The left horn of the sinus venosus becomes what?
the coronary sinus
The portal vein in liver develops from what?
vitelline veins
What is the ductus venosus?
a channel through the liver that allows blood from the left umbilical vein directly through the liver to the inferior vena cava
What happens to the left umbicial vein in the liver?
- at first it enlarges to become the ductus venosus
- then it involutes after birth to form the ligamentum venosum
The ductus venosus is derived from what embryonic vein?
the left umbilical vein
Prior to birth, what are the two shunts that allow right to left blood flow to bypass the fetal lung?
- foramen ovale
- ductus arteriosus
What role does bradykinin play in the cardiovascular system immediately at birth?
it serves to decrease the vascular resistance within the lung as the oxygen source changes
What happens to right arterial pressure just after birth?
it declines as umbilical blood flow is lost
What molecule reduces the vascular resistance of the lungs just after birth?
bradykinin
What is indomethican?
a prostaglandin inhibitor given to speed up the closure of the patent ductus arteriosus
Why would transposition of the great arteries be treated with prostaglandin?
prostaglandin will slow closure of the ductus arteriosus allowing some oxygenated blood from the right ventricle to reach the systemic arteries
A machine like murmur present during systole and diastole and cyanosis of just the toes is indicative of what?
patent ductus arteriosus
