L7: Development of the CVS Flashcards
Define septation?
Divisions of cavities by means of partitioning
What needs to be separated in the primordial heart? What structures are responsible for this?
Atria–> Interatrial septum
Ventricles –> Interventricular septum
Outflow tracts –> Pulmonary trunk and aorta
What is the first step in septation?
Separation into left and right chambers
Level of atrioventricular region
Endocardial cushions–> grow–> meet in midline
Endocardial cells –> neural crest cells
What happens in atrial septation?
Division into right and left
Septum primum–> grows towards endocardial cushion
Ostium primum–> hole –> before septum primum and endocardial cushion fuse
Ostium secundum–> in septum primum near top–> before ostium primum closes
Septum primum–> fuses with endocardial cushion
Septum secundum–> crescent shaped–> hole in septum called foramen ovale
(blood can flow from R - L through the foramen ovale and the ostium secundum)
Why is atrial septation complex?
Building de nove structure
Needs shunt from RA to LA
Close straight after birth
What is it called if the foramen ovale doesn’t close properly?
Probe patent fossa ovalis
20% population
What causes the fossa ovalis to close at birth?
Pressure in LA↑ as lungs work»_space; Pressure in RA
Septum primum pushed against spetim secundum
What are some of the atrial septum defects?
Ostium secundum defect–> hole in interatrial wall
Caused by:
–> Septum primum–> resorbed or too small
–> Septim secundum–> too small or absent
–> Absence of spetum primum and secundum
What is hypoplastic left heart syndrome?
Left heart is small, underdeveloped or both
Exact causes unknown
Potentially:
–> Defect in mitral and aortic valves
–> Atresia –> abnormal or narrowing of valve
–> Reduced blood flow
–> Ostium secundum too small
–>R-L flow inadequate –> left side of heart not used in development –> underdeveloped
How do the ventricles separate?
Muscular part –> majority –> grows upwards –> leaves small gap
Membranous part–> connective tissue –> from endocardial cushion
What are the ventricle septal defects?
Membranous part doesn’t develop properly
How does the outflow tracts separate?
Endocardial cushion appear in truncus arteriosus
Different levels –> different orientation
Grow towards–> twist
Spiral septum
What can cause congenital heart defects?
Structural abnormalities –> Morphology wrong
Absence of structure
Interference/ interuption of normal development
Caused by: Genetics, exposure to chemicals/ drugs/ infection agents (rubella toxoplasma) or unexplained
What defects can there be in the heart? Why are there additional problems compared to other systems?
Defects of chambers or vasculature, obstruction, communication between pulmonary and systemic circulation
Complex–> different circulatory needs of fetus vs newborn
How common are congenital heart defects?
Most common
Worldwide incidence =1%
90% survive to adulthood
