22. Heart Tube and Septal Defects

Question 1

When does the fetal vascular system appear

Answer 1

Middle of the third week

Question 2

Where do cardiac progenitor cells comes from?

Answer 2

Epiblast

Question 3

What forms the primary heart field?

Answer 3

Cardiac progenitor cells from the splanchnic layer of lateral plate mesoderm

Question 4

What arises from the primary heart field?

Answer 4

Atria, left ventricle, part of right ventricle

Question 5

What forms the secondary heart field?

Answer 5

Cardiac progenitor cells from pharyngeal mesoderm

Question 6

What arises from the secondary heart field?

Answer 6

Remainder of right ventricle and outflow tract

Question 7

When does the heart tube begin to bend?

Answer 7

23 days

Question 8

What is the cranial bulge called?

Answer 8

Bulbus cordis

Question 9

What is the caudal bulge called?

Answer 9

Primitive ventricle

Question 10

How does the heart bend?

Answer 10

Top bends towards the right
Bulboventricular part becomes u-shaped
Bulbus cordis forms right part
Primitive ventricle forms left
Junction is called bulboventricular sulcus

Question 11

What does the proximal bulbus cordis become?

Answer 11

trabeculated part of the right ventricle

Question 12

What does the conus cordis become?

Answer 12

Outflow tract of both ventricles

Question 13

What does the truncus arteriosis form?

Answer 13

Roots and proximal portion of aorta and pulmonary artery

Question 14

What is the sinus venosus?

Answer 14

Cavity which precedes as the SA node and coronary sinus

Question 15

What does each sinus horn have?

Answer 15

Vitelline vein (left vanishes)
Umbilical vein (right vanishes)
Common cardial vein

Question 16

Describe the formation of the septum primum

Answer 16

Sickle shaped crest grows from the roof of the common atrium
2 limbs of the septum extend towards endocardial cushions in the atrioventricular canal
Extensions of superior and inferior endocardial cushions grow along edge of septum primum to close the ostium primum

Question 17

What is the name of the opening between the lower rim of the septum primum and endocardial cushions?

Answer 17

Ostium primum

Question 18

Describe the formation of the septum secundum

Answer 18

Before the septum primum completely closes, cell death produces holes at the top
Holes join to form ostium secundum, ensuring free blood flow from right to left primitive atrium
The new crescent shaped fold is called the septum secundum
This begins to overlap with the ostium secundum
Opening is called foramen ovale
Upper part of the septum primum disappears
Passage left through atrial cavities with a cleft through which blood flows from the RA to LA

Question 19

How is the ventricular septum formed?

Answer 19

Primitive ventricles expand

Medial walls merge, forming a muscular interventricular septum

Question 20

Name 3 atrial septal defects

Answer 20

Left to right shunting of blood
Ostium primum defect
Ostium secundum defect

Question 21

Name 5 ventricular septal defects

Answer 21

Ventricular spetal defect
Left to right shunt
Persistant truncus arteriosis
Tetralogy of Fallot
Transposition of the great vessels