Cardiac embryology

Question 1

What is Dextrocardia?

Answer 1

Heart points toward the right side of your chest instead of the left side

Question 2

What happens regarding fetal vessels by end of week 3? What day does the heart start beating?

Answer 2

Blood vessels develop in the extraembryonic mesoderm which forms parts of the placenta and umbilical cord
Note: block flow starts week 4
Heart starts beating day 22-23

Question 3

In the embryonic disc, where does the heart develop?

Answer 3

Towards the cranial side, at the heart primordium (primary heart field)

Question 4

Describe the process of heart tube formation.

Answer 4

Angioblastic cords canalise to form two heart tubes, which merge together, these tubes then expand.
Heart tube folds as it grows and becomes surrounded by the serous pericardium

Question 5

During heart tube folding, which way does the bulbus cordis and ventricle move? What if they fold the opposite way?

Answer 5

Bulbus cordis moves to the right
Ventricle moves to the left
Opposite - dextrocardia

Question 6

What part of the heart do these contribute to?
Sinus Venosus
Atria
Ventricle
Bulbus Cordis
Truncus Arteriosus

Answer 6

Sinus Venosus - smooth wall of R.atria
Atria - Rough wall of both atria
Ventricle - ventricles
Bulbus Cordis - Outflow tracts of both ventricles
Truncus Arteriosus - Initial part of Aorta and PT

Question 7

What forms to divide the chambers and outflow tracts to create left and right sides of the heart?

Answer 7

Septa

Question 8

What forms the smooth part of the right and left atrial wall?

Answer 8

Right - right horn of the sinus venosus

Left - growth into the pulmonary veins

Question 9

Where are the two core bypass points/vascular shunts that exist in the embryonic heart to bypass the developing lungs?

Answer 9

1. From right atria to left atria

2. From pulmonary trunk to aorta (ductus arteriosus)

Question 10

What week does atrial septation occur?

Answer 10

Weeks 4 and 5

Question 11

What are endocardial cushions?

Answer 11

or atrioventricular cushions, refer to a subset of cells in the development of the heart that play a vital role in the proper formation of the heart septa.

Question 12

How does the atrial septum form?

Answer 12

Atrial septum forms from two separate sheets of tissue that grow through the atrium to the endorcardial cushion.
Septum primum -> Foramen Secundum -> Septum secundum -> Foramen ovale

Question 13

How does pressure on the right/left side of the heart change after birth?

Answer 13

In utero - higher pressure on right side (lungs are fluid filled)
Postnatal - higher pressure on left side
Blood shunting in utero through foramen ovale is pressure-gradient driven

Question 14

What can an atrial septal defect (ASD) lead to? and where can it occur?

Answer 14

Leads to left - to - right shunting after birth

Can occur in Septum secundum/primum and endocardial cushion

Question 15

What is it called when the tissues of the atrial septa do not close after birth?

Answer 15

Probe-patent foramen ovale

Question 16

What can the valsava manoevure sometimes cause in terms of the heart, when the patient has a probe-patent foramen ovale?

Answer 16

Briefly increase right sided pressure over that of the left resulting in an emboli passing from right to left - stroke?

Question 17

What is the ventricular septum formed of? Which part are defects more likely to occur and why?

Answer 17

Muscular and membranous parts

Membranous part - more complicated e.g. twisting

Question 18

What is special about the septum that divides the aorta and pulmonary trunk? (articopulmonary septum)

Answer 18

The ventricular and common arterial outflows are divided into the aorta and pulmonary trunk by a septum that rotates through 180º

Question 19

What does malrotation or malformation of the articopulmonary septum result in?

Answer 19

Tetralogy of fallot
Transposition of the great vessels
Common/persistent trunks arteriosus

Question 20

What does the ductus arteriosis do? (What is patent DA)?

transposition of the great vessels

Answer 20

blood vessel in the developing fetus connecting the pulmonary artery to descending aorta. It allows blood from the right ventricle to bypass the fetus’s fluid-filled lungs.
Patent DA - fails to close after birth

Question 21

What is common truncus arteriosus/persistent truncus?

Answer 21

Failure of bulbar ridge formation in common arterial flow
Cyanotic condition
occurs when the single large blood vessel fails to divide into two arteries during fetal development.

Question 22

What 4 things cause tetralogy of fallot? (Hint: PROV)

Answer 22

1. Pulmonary stenosis
2. RV hypertrophy
3. Over-riding aorta
4. Ventricular septal defect