Development of the Heart Flashcards
What type of mesoderm does the heart form from?
Splanchnic mesoderm
In the cranial end
When does the heart start to develop?
Late in the 3rd week following fertilization
First organ to function!
What folding directions brings the heart to the correct placement?
Lateral folding brings the two endocardial tubes together
Craniocaudal folding brings heart to thorax
Primary heart tube
Formed from the fusion of the endocardial tubes
When it is brought to the correct position
What day does the
- Heart start to beat
- Heart start to fold
- Day 22
2. Day 23
3 mechanisms that contribute to heart folding
Constraints on the upper and lower tube that force bending
Twisting movement
Disproportional addition of cells
What constrains the heart at the
1. Cranial
2. Caudal
ends?
- Blood vessels
2. Septum transversum
Situs inversus
All the internal organs are changed to the opposite site
When does cardiac folding occur?
During the 4th week after fertilization (day 23-28)
Dextrocardia
When the heart points towards the right side of the body
Endocardial cushions
Blocks of myocardium
Separate AV opening into L and R channels
When does AV partitioning occur?
Between 4 to 8 weeks
How do the atria separate?
Formation of septum primum to block off foramen primum
Hole at top forms (foramen secundum)
On the right side, a second foramen forms (foramen secundum)
Foramen secundum does not close completely, leaves the foramen ovale open a the inferior surface
The remaining part of the septum primum becomes the valve of the foramen ovale
What side of the septum primum does the septum secundum form?
The right side
2 parts of the interventricular septum
Membranous
Muscular
