Lecture 5 Flashcards
Where does the heart develop from?
Cardiogenic Mesoderm
-This gives rise to the myocardium and epicardium
What will the primitive heart tube form?
Endocardium
What suspends the heart tube?
Dorsal medocardium
How is the transverse pericardial sinus formed?
endoApoptosis of the central part of the dorsal mesocardium –> Creates a communication between the left and right sides of the pericardium
Dextrocardia w/ situs inversus
-Heart loops at 4 weeks gestatation
Normal:
D-look Positions apex to left
Abnormal:
-L-loop positions apex to right or Dextrocardia
-Situs inversus –> abdominal organs are also found reversed
Dextrocardia
Normal:
D-look Positions apex to left
Abnormal:
-L-loop positions apex to right or Dextrocardia
What does the sinus venosus form?
Right Horn:
1) Smooth walled/right atrium
Left Horn:
2) Coronary sinus
What does the primitive atrium form?
Right:
1) Rough walled part of right atrium
Left:
1) Rough walled part of left atrium
What does the primitive ventricle form?
Right:
1) Trabeculated (Rough) part of the right ventricle
Left:
1) Trabeculated (Rought) part of the left ventricle
What does the Bulbos cordis form?
Right:
1) Conus arteriosus
Left:
1) Aortic vestibule
What does the truncus arteriosus form?
Right:
1) Pulmonary trunk
Left:
1) Ascending aorta pulmonary arter
When do endocardial cushions form and where are they derived from?
4th-5th week
-Derives from cardiac mesenchyme
What do the endocardial cushions form?
- Fuse tg to form right and left AV canals
- Also form mitral and tricuspid valves, Aortic/pulmonary valves, atrial and ventricular septum
How can downs syndrome (Trisomy 21) develop?
-Defects in endocardial cushions –> Problems w/ septum forming
How is the oval foramen formed?
By the septum secundum and the foramen secundum
What is the significance of the sinus venarum?
- Absorbed by the right atrium
- Becomes the smooth part (Right horn) of the right atrium where the superior vena cava and inferea vena cava enter
What forms left atrium
1) Primitive atrium
2) Primitive pulmonary veins
What forms the right atrium
1) Primordial atrium
2) Sinus’s venosus
What forms the limbus?
Septum secundum
Atrial Septal Defects
Foramen ovale
1) Probe patent foramen ovale
- Failure of fusion of septum primum and secundum
Atrial Septal Defects
Ostium secundum type ASD’s are defects of the oval fossa :
- Defect in septum secundum→ large foramen ovalis
- Excessive resorption of septum primum→ short septum primum
- Excessive reabsorption of septum primum and abnormally large foramen ovale
- Abnormal reabsorption of the septum primum→ fenestrations SP
Atrial Septal Defect
Primum type
-Failure of closure of foramen primum
Atrial Septal Defects
Common Atrium
Failure of septum primum and secundum to develop
Atrial Septal Defects
Sinus venosus type
1) Incomplete resorption of
sinus venosus into right atrium
OR
2) Abnormal development of upper part of septum secundum
