Embryology of the CVS Flashcards
What are the main stages of the development of the CVS?
- Development of primitive heart tube
- Looping of the heart tube
- Atrial and ventricular septation
- Development of the outflow tract
What occurs in the 3rd week of development?
Lateral plate splanchnic mesoderm forms circulatory system (and other viscera).
How do angiogenic cell islands form the two primitive heart tubes?
Angiogenic cell islands collect in the lateral plate splanchnic mesoderm, move towards the midline and coalesce to form the two primitive heart tubes
When does the premordial heart start to function?
It starts to function at the beginning of the 4th week.
Where do blood vessels first appear?
- They first appear in the wall of yolk sac, allantois, connecting stalk and chorion.
- Appearance of paired endothelial strands (angioblastic cords) appear in the cardiogenic mesoderm at 3rd week
What do Angioblastic cord become?
Angioblastic cords canalise to form heart tubes.
-Tubular heart joins blood vessels in other areas to form primordial cardiovascular system
What is the pericardium formed from?
- It is derived from intra-embryonic coelom.
- Parietal layer of serous pericardium & fibrous pericardium are formed from somatic mesoderm.
- Visceral layer of serous pericardium is derived from splanchnic mesoderm.
In the embryo, what way does the cranial end (arterial) face?
Cranial ends faces towards the head of the embryo
In the embryo, what way does the caudal end (venous) face?
Caudal end faces towards the tail of the embryo
In the fused primitive heart tube what way do the bulbus cordis and ventricle face?
Bulbus cordis folds towards the right so ventricle moves to the left!
Features of the sinus venosus (venous end)
- Two horns: right and left
- Each horn gets venous blood from: yolk sac(=vitelline v.), Placenta(=umbilical v.), Body of the embryo (=common cardinal v.)
Features of the Truncus arteriosus (arterial end)
- Continuous cranially with the aortic sac.
- Aortic arches arise from the aortic sac.
- Aortic arches terminate in the dorsal aorta.
How does the cardiac (Bulboventricular) loop form?
Bulbus cordis and ventricle grow faster than other regions forming a U-shaped
bulboventricular loop.
Day 22-24
Describe dextrocardia (abnormal cardiac looping)
- Heart tube loops to the left side (instead of right), thus coming to lie facing the right (=dextro).
- Dextrocardia can be associated with situs inversus (transposition of viscera)
What are the 2 forms of partitioning of Primordial heart?
- Endocardial cushion formation - separates right atrium + ventricle from left atrium + ventricle to form L&R AV canals.
- Septum formation- separates right atrium from left atrium + right ventricle from left ventricle.
Clinical - e.g. atrial septal defect (ASD) & ventricular septal defect (VSD)