cardiac embryology Flashcards
Where are the precardiac cells located at the blastocyst stage
within the epiblast on either side of the primitive streak.
Where are the precardiac cells located at the gastrula stage
mesoderm
Where is the cardiogenic area at day 16 of development
Cranial end: derived from mesoderm and represents the cells that will form the CV system
When does the heart begin to beat
Day 22
Name the 4 main regions of the heart present during the 4th week of development and what it will become
Truncus (Aortic/ pulmonic valves, ascending aorta, pulmonary trunk), Bulbus cordis (trabeculated portion of RV) , Primitive ventricle (Trabeculated portion of LV) and primitive atria (Left and Right atrial appendages)
Pre loop stage- components
Straight heart tube with an atrioventricular sulcus (becomes intraventricular septum), primitive ventricle (LV), and Bulbus cordis (RV). Blood flow begins.
Describe the components of the heart tube
inner layer: endotelial lining which becomes endocardium. Outer layer: mesoderm that will develop into myocardium and epicardium. Cardiac jelly: btw inner and outer layer, plays a role in looping ad septation
describe heart looping
The cardiac tube grows at a greater longitudinal rate than the rest of the embryo resulting in looping of the heart. Normally, heart loops to the right of the embryo (D-loop). Primitive atria rotate posteriorly so that the long axis is now posterior to anterior. Day 23-35
The cardiac tube grows at a greater longitudinal rate than the rest of the embryo resulting in looping of the heart. Normally, heart loops to the right of the embryo (D-loop). Primitive atria rotate posteriorly so that the long axis is now posterior to anterior. Day 23-35
Post loop stage
Septation begins
Which veins drain into the sinus venosus at day 25
Umbilical vein from placenta, Vitelline vein from yolk sac, cardinal vein from embryo.
What does the pulmonary veins develop from
An endothelial projection from LA connects to the pulmonary venous plexus to form common pulmonary vein which then branches
Describe when and how the endocardial cushions grow to bissect the atrioventricular canal
Post loop stage (28-42 days). Abnormalitis results in septal defects. The atrial septum fuses with the endocardial cushions (involved in ventricular septation)
Describe how and when the truncus arteriosus is subdivided into the pulmonary and aortic outflow tracts
Days 35-56: Two masses appear in the truncus, a right and left intercalated swellings (which become the noncoronary aortic cusp and anteriior pulmonary cusp respectively). Septation of the pulmonary artery and aorta occurs in a spiral.
Ascending aorta comes from the ____________ and the descending aorta comes from the _______________
Ascending aorta comes from the ____________ and the descending aorta comes from the _______________
aortic sac, left dorsal aorta
Describe the components of the embryonic heart that contribute to septation of the ventricles, and identify when this separation occurs
During early post loop stage (day 26-28).
Describe how and when the left and right atria are separated.
Days 28-42
Identify which aortic arch vessels are lost, and which are maintained by 8 weeks gestation, and what are the anatomical names of the remaining vessels
Aortic arches 1,2, and 5 disappear. 3rd becomes carotid arteries, 4th becomes right brachiocephalic and right subclavian arteries (right side) and transverse aortic arch (left side), 6th becomes proximal right pulmonary artery, proximal left pulmonary artery and ductus arteriosus
Identify 2 components of fetal cardiac circulation which are no longer patent after birth
Ductus arteriosus shunts blood from the pulmonary artery to the aorta (to prevent blood from going to the lungs) and the ductus venosus shunts blood from umbilical vein to inferior vena cava
What embryonic structure does the ductus arteriosus come from
distal portion of left 6th aortic arch
Describe functional closure of the ductus arteriosus
In 12 hrs after birth, increased oxygen pressure in pulmonary artery leads to Contraction and cellular migration of the medial smooth muscle in the wall of the ductus causing intimal thickening with protrusion into the lumen.
Describe anatomical closure of the ductus arteriosus
By 2-3 weeks: The internal elastic membrane of the ductus fragments, the intima and media proliferate, mucoid lakes form in the intima and media hyaline mass forms that totally occludes the lumen.
What can cause the ductus arteriosus to stay open
Prostaglandins: vasoactive agents from ductal wall and/or placenta
Left to right shunt
Blood flow from systemic chamber (pulmonary vein, left atrium, left ventricle or aorta) into pulmonary chamber (systemic veins, right atrium, right ventricle or pulmonary arteries).
Clinical presentation of patent ductus arteriosus in infant
Asymptomatic, respiratory effects (pulmonary edema/hemorrhage), congestive heart failure, feeding intolerance, renal insufficiency, death
Clinical presentation of patent ductus arteriosus in young child
hoarse cry, pneumonias, failure to thrive, increased work of breathing, diaphoresis with activity
Physical exam of patent ductus arteriosus
Systolic ejection murmur (left upper sternal border) w/ or w/out diastolic rumble if shunt is large. Accentuated P2 if there is pulmonary HTN
Treatment of patent ductus arteriosus
Asymptomatic neonate: conservative. Symptomatic neonate: COX inhibitors or surgical ligation. Symptomatic older child: percutaneous occlusion
