Embryology of the CVS 1 Flashcards
What are the main stages in the embryology of the CVS?
1) Development of primitive heart tube
2) Looping of the heart tube
3) Atrial and ventricular septation
4) Development of the outflow tract
In what week does the lateral plate splanchnic mesoderm form the circulatory system?
3rd
What does the lateral plate mesoderm form in the 3rd week?
Circulatory system
In what week are the 2 primitive heart tubes formed?
3rd
What happens during the 3rd week that leads to the formation of the two primitive heart tubes?
Angiogenic cell islands collect in the lateral plate splanchnic mesoderm move towards the midline and coalesce to form the 2 primitive heart tubes
What is the first major system to function in the embryo?
Cardiovascular
In what week does the primordial heart start to function?
Beginning of the 4th week
What does the primordial heart start to function at the beginning of the 4th week?
The rapidly growing embryo cannot get enough nutrition by diffusion anymore
What is the cardiogenic field?
Primitive heart and blood vessels of the embryo
What is the primitive heart and blood vessels of the embryo called?
Cardiogenic field
What is the process of the formation of the cardiogenic field?
1) Blood vessels first appear in the wall of the yolk sac, allantois, connecting stalk and chorion
2) Appearance of paired endothelial strands (angioblastic cords) appear in the cardiogenic mesoderm in the 3rd week
3) Angioblastic cords canalise to form heart tubes
4) Tubular heart joins blood vessels in other areas to form primordial cardiovascular system
Where do blood vessels first appear?
Yolk sac
Allantois
Connecting stalk
Chorion
What are angioblastic cords?
Paired endothelial strands
When do angioblastic cords appear in the cardiogenic mesoderm?
3rd week
What does formation of the pericardium occur due to?
Cranial folding of the embryo
What does cranial folding of the embryo cause?
Reorientation of the heart tube dorsal to the pericardial cavity
What is the pericardium derived from?
Intra-embryonic coelom
What is the parietal layer of the serous pericardium and fibrous pericardium derived from?
Somatic mesoderm
What is the visceral layer of the serous pericardium derived from?
Splanchnic mesoderm
Where does the pericardial cavity go from and to after cranial folding?
Dorsal to ventral
Where does the cardiac tube go from and to during cranial folding?
Ventral to dorsal
What are the two ends of the primitive heart tube?
Cranial end (arterial)
Caudal end (venous)
What is 1?
Trancus arteriosus
What is 2?
Bulbus cordis
What is 3?
Ventricle
What is 4?
Atrium
What is 5?
Sinus venosus (right and left horns)
What is this a diagram of?
Fused primitive heart tube
Why does the primitive heart tube need to fold?
Pericardium is too small to hold it
Why does the heart face left?
Due to the way that the primitive heart tube folds to the right
In what direction does the primitive heart tube fold?
Right (causing the heart to face left)
What does the trancus arteriosus continue cranially from?
Aortic sac
What arises from the aortic sac?
Aortic arches
Where does the aortic arches terminate?
Dorsal aorta
How many arches does the trancus arteriosus form?
6
Are the arches labeled from closes to trancus arteriosus or furthest away?
Furthest away is first, closest is sixth
What is the sinus venosus composed of?
Left and right horn
What does each horn of the sinus venosus get blood from?
Yolk sac (by the vitelline vein)
Placenta (by the umbilical vein)
Body of the embryo (by the common cardinal vein)
What gives the sinus venosus blood from the yolk sac?
Vitelline vein
What gives the sinus venosus blood from the placenta?
Umbilical vein
What gives the sinus venosus blood from the body of the embryo?
Common cardinal vein
What does the cardiac (bulboventricular) loop form due to?
Bulbus cordis and ventricle growing faster than the other regions of the primitive heart tube
What is dextrocardia?
Heart points to the right side of the chest instead of the left side
What is it called when the heart points to the right side of the chest instead of the left side?
Dextrocardia
What happens during dextrocardia?
Heart tube loops to the left side instead of the right (so ends up to lie facing the right)
What is the most frequent positional abnormality of the heart?
Dextrocardia
What can dextrocardia be associated with?
Situs inversus (transposition of viscera)
When does partitioning of the primordial heart occur?
27th day of embryonic development
What does partitioning of the primordial heart involve?
One or two actively growing masses of tissues:
Endocardial cushion formation
Septum formation
What does the endocardial cushion do?
Seperates right atrium and ventricle from left atrium and ventricle, forming left and right AV canals
What seperates right atrium and ventricle from left atrium and ventricle to form left and right AV canals?
Endocardial cushion
What does the septum formation do?
Separates right atrium from left atrium and right venticle from left ventricle
What separates right atrium from left atrium and right ventricle from left ventricle?
Septum formation
What are cardiac malformations associated with defective formation of endocardial cushion and septum formation?
Atrial septal defect (ASD)
Ventricular septal defect (VSD)
What does ASD stand up for?
Atrial septum defect
What does VSD stand up for?
Ventricular septal defect
What is A?
Septum primum
What is B?
Foramen primum
What is C?
Left atrioventricular canal
What is D?
Fused endocardial cushions
What is E?
Primordial interventricular septum
When does partitioning of the primitive atrium into left and right atria occur?
Starts towards the end of the 4th week
What develops during the partition of the primitive atrium?
1) Septum primum and foramen primum
2) Septum secundum and forament secundum
What is another word for foramen?
Ostium
What is the process of the formation of the septum primum and foramen primum?
1) Crest grows from the roof of atrium (septum primum)
2) Opening between septum primum and endocardial cushion
Where does the foramen secundum form and why?
Upper end of the septum primum due to cell death
Where does the septum secumdum form?
Right side of septum primim
How does the septum secundum grow?
Grows down and overlaps the forament secundum, but the septum secundum is incomplete being perforated (pierced) by the oval foramen (foramen ovale)
What is the difference between the foramen secundum and the foramen ovale?
Foramen secundum is the opening in the septum primum
Foramen ovale is the opening in the septum secundum
What is the process of atrial partitioning?
1) Formation of septum primum and foramen primim
2) Formation of foramen secundum
3) Formation of septum secundum
4) Septum secundum grows down and overlaps foramen secundum, but it is incomplete due to being pierced by oval foramen (foramen ovale)
What is the role of the oval foramen before birth?
Allows most of the blood to pass from the right atrium to the left atrium (non-functioning lungs)
Prevents the passage of blood in the opposite direction
What happens to the oval foramen after birth?
Normally closes (increased pulmonary blood flow and shift of pressure to the left atrium)
What happens to the septum primum after birth?
Fuses with the septum secundum
What of the adult heart is the remnant of the oval foramen?
Oval fossa
What does non closure of the oval foramen after birth result in?
Atrial septal defect (ASD)
Is atrial septal defect (ASD) more common in males or females?
Females
What are the 4 clinically significant types of atrial septal defect (ASD)?
Foramen secundum defect
Endocardial cushion defect with foramen primum defect
Sinus venosus defect
Common atrium
What are the 2 most common kinds of atrial septal defect (ASD)?
Foramen secundum defect
Endocardial cushion defect with foramen primum defect
What is the process of the partitioning of the primitive ventricle?
1) Muscular ventricular septum forms, opening is called the interventricular foramen
2) Bottom of spiral aorticopulmonary septum fuses with muscular ventricular septum to form membranous interventricular septum, closing interventricular foramen (aorticopulmonary septum divides bulbis cordis and truncus arteriosus into aorta and pulmonary trunk)
3) Growth of endocardial cushions also contributes to membranous portion of the interventricular septum
What does the aorticopulmonary septum divide the bulbis cordis and truncus arteriosus into?
Aorta and pulmonary trunk
What forms the valve of the oval foramen?
Septum primum
What is the interventricular septum composed of?
Membranous portion
Muscular portion
During what week does the aorticopulmonary septum divide the bulbis cordis and truncus arteriosus into the aorta and pulmonary trunk?
5th week
What is the most common kind of congenital heart disease?
Ventricular septal defect (accounts for 25% of defects)
Is ventricular septal defect (VSD) more common in male or females?
Males
What can happen to small ventricular septal defects?
Close spontaneously (30-50% of the time)
What are primitive pacemakers?
Primitive atrium and then sinus venosus
When does the SA node develop?
5th week
Where is the adult location of the SA node?
High in the right atrium near the entrance of the superior vena cava
What does the AV node and bundle of His develop from?
Cells of AV canal and sinus venosus
What does cot death or sudden infant death syndrome (SIDS) often occur due to?
Abnormalities of conducting tissue
What does the aortic sac go on to form?
Aortic arches
What is aortic arches derived from?
Aortic sac
What does the bulbus cordis go onto form?
Right ventricle
Parts of the outflow tract
What is the right ventricle and parts of the outflow tract derived from?
Bulbus cordis
What does the primitive ventricle go on to form?
Left ventricle
What is the left ventricle derived from?
Primitive ventricle
What does the primitive atrium go onto form?
Parts of the upper and left atria
Whats are parts of the upper right and left atria derived from?
Primitive atrium
What does the sinus venosus go onto form?
Superior vena cava
Right atrium
What is the superior vena cava and right atrium derived from?
Sinus venosus
How can the aetiology of congenital heart disease be described?
Multifactorial
What are some possible causes for congenital heart disease?
Rebella infection in pregnancy
Maternal alcohol abuse (septal defects)
Maternal drug treatment and radiation
Genetic (8%)
Chromosomal such as Down’s syndrome and Turner’s syndrome (2%)
What can maternal alcohol abuse lead to?
Septal defects
What percentage of congenital heart diseases are VSDs and ASDs?
30% (20% for VSD and 10% for ASD)
What is a common cause of cyanotic disease in new born infants?
Transposition of great vessels
What does transposition of great vessels permit?
Exchange between systemic and pulmonary circulation
What are some causes of transposition of great vessels?
Failure of aorticopulmonary septum to take spiral course
Defective migration of neural crest cells
What leads to the formation of the SA node?
Migration of neural crest cells
What does Tetralogy of Fallot cause?
Low oxygenation of blood
What are the 4 cardiac defects that make up the tetralogy of Fallot?
Pulmonary stenosis (obstruction of right ventricular outflow)
Ventricular septal defect
Dextroposition of aorta
Right ventricular hypertrophy
What are examples of congenital heart diseases?
Atrial septal defect
Ventricular septal defect
Transposition of great vessels
Tetralogy of Fallot
