cardiac embryology

Question 1

Where are the precardiac cells located at the blastocyst stage

Answer 1

within the epiblast on either side of the primitive streak.

Question 2

Where are the precardiac cells located at the gastrula stage

Answer 2

mesoderm

Question 3

Where is the cardiogenic area at day 16 of development

Answer 3

Cranial end: derived from mesoderm and represents the cells that will form the CV system

Question 4

When does the heart begin to beat

Answer 4

Day 22

Question 5

Name the 4 main regions of the heart present during the 4th week of development and what it will become

Answer 5

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)

Question 6

Pre loop stage- components

Answer 6

Straight heart tube with an atrioventricular sulcus (becomes intraventricular septum), primitive ventricle (LV), and Bulbus cordis (RV). Blood flow begins.

Question 7

Describe the components of the heart tube

Answer 7

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

Question 8

describe heart looping

Answer 8

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

Question 9

Post loop stage

Answer 9

Septation begins

Question 10

Which veins drain into the sinus venosus at day 25

Answer 10

Umbilical vein from placenta, Vitelline vein from yolk sac, cardinal vein from embryo.

Question 11

What does the pulmonary veins develop from

Answer 11

An endothelial projection from LA connects to the pulmonary venous plexus to form common pulmonary vein which then branches

Question 12

Describe when and how the endocardial cushions grow to bissect the atrioventricular canal

Answer 12

Post loop stage (28-42 days). Abnormalitis results in septal defects. The atrial septum fuses with the endocardial cushions (involved in ventricular septation)

Question 13

Describe how and when the truncus arteriosus is subdivided into the pulmonary and aortic outflow tracts

Answer 13

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.

Question 14

Ascending aorta comes from the ____________ and the descending aorta comes from the _______________
Ascending aorta comes from the ____________ and the descending aorta comes from the _______________

Answer 14

aortic sac, left dorsal aorta

Question 15

Describe the components of the embryonic heart that contribute to septation of the ventricles, and identify when this separation occurs

Answer 15

During early post loop stage (day 26-28).

Question 16

Describe how and when the left and right atria are separated.

Answer 16

Days 28-42

Question 17

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

Answer 17

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

Question 18

Identify 2 components of fetal cardiac circulation which are no longer patent after birth

Answer 18

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

Question 19

What embryonic structure does the ductus arteriosus come from

Answer 19

distal portion of left 6th aortic arch

Question 20

Describe functional closure of the ductus arteriosus

Answer 20

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.

Question 21

Describe anatomical closure of the ductus arteriosus

Answer 21

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.

Question 22

What can cause the ductus arteriosus to stay open

Answer 22

Prostaglandins: vasoactive agents from ductal wall and/or placenta

Question 23

Left to right shunt

Answer 23

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).

Question 24

Clinical presentation of patent ductus arteriosus in infant

Answer 24

Asymptomatic, respiratory effects (pulmonary edema/hemorrhage), congestive heart failure, feeding intolerance, renal insufficiency, death

Question 25

Clinical presentation of patent ductus arteriosus in young child

Answer 25

hoarse cry, pneumonias, failure to thrive, increased work of breathing, diaphoresis with activity

Question 26

Physical exam of patent ductus arteriosus

Answer 26

Systolic ejection murmur (left upper sternal border) w/ or w/out diastolic rumble if shunt is large. Accentuated P2 if there is pulmonary HTN

Question 27

Treatment of patent ductus arteriosus

Answer 27

Asymptomatic neonate: conservative. Symptomatic neonate: COX inhibitors or surgical ligation. Symptomatic older child: percutaneous occlusion