Embryology Timeline

Question 1

Angiogenic cell clusters lie in cardiogenic plate

Answer 1

Day 16/17 (week 3)

Question 2

Endocardial tubes are formed and move towards each other

Answer 2

Day 18-20 (Week 3)

Question 3

Endocardical tubes begin to fuse and forced into thoracic region

Answer 3

Day 21-22 (Week 3)

Question 4

Single heart tube formed, heart begins to beat, pericardial cavity formed

Answer 4

Day 22 (Week 4)

Question 5

Heart tube grows rapidly, forcing it to fold upon itself (Bulboventricular loop formed)

Answer 5

Day 23 (Week 4)

Question 6

Centrally located sinoatrial junction begins to shift to the right

Answer 6

Day 24 (Week 4)

Question 7

The bulboventricular loop is completed, septum primum appears

Answer 7

Day 25-28 (Week 4)

Question 8

Ventricular septum appears as small ridge, ventricles begin to dilate, single pulmonary artery grows from LA, endocardial cushions appear

Answer 8

Day 28 (Week 4)

Question 9

Truncal swellings appear

Answer 9

Day 29 (Week 5)

Question 10

Perforations appear in septum primum

Answer 10

Day 30-31(Week 5)

Question 11

Bulboventricular flange begins to recede, AV canal gains “dog’s bone” appearance, ostium secundum formed by free edge of septum primum

Answer 11

Day 32-33 (Week 5)

Question 12

Sinoatrail junction completely shifted to the right

Answer 12

Day 35 (Week 5)

Question 13

The septum secundum ceases to grow; its free edge forms the foramen ovale

Answer 13

Day 37 (Week 6)

Question 14

Superior and inferior endocardial cushions fuse

Answer 14

Day 42 (Week 6)

Question 15

The ventricular septum ceases to grow, the coronary sinus is formed

Answer 15

Day 46 (Week 7)

Question 16

The interventricular canal is completely obliterated

Answer 16

Day 48-49 (Week 7)

Question 17

The outflow tracts (aorta and pulmonary trunk) are completely separated

Answer 17

Early in week (Week 8)