Embryology of the CVS 1 Flashcards by Becca M

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

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In what week does the lateral plate splanchnic mesoderm form the circulatory system?

3rd

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What does the lateral plate mesoderm form in the 3rd week?

Circulatory system

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In what week are the 2 primitive heart tubes formed?

3rd

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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

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What is the first major system to function in the embryo?

Cardiovascular

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In what week does the primordial heart start to function?

Beginning of the 4th week

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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

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What is the cardiogenic field?

Primitive heart and blood vessels of the embryo

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What is the primitive heart and blood vessels of the embryo called?

Cardiogenic field

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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

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Where do blood vessels first appear?

Yolk sac

Allantois

Connecting stalk

Chorion

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What are angioblastic cords?

Paired endothelial strands

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When do angioblastic cords appear in the cardiogenic mesoderm?

3rd week

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What does formation of the pericardium occur due to?

Cranial folding of the embryo

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What does cranial folding of the embryo cause?

Reorientation of the heart tube dorsal to the pericardial cavity

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What is the pericardium derived from?

Intra-embryonic coelom

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What is the parietal layer of the serous pericardium and fibrous pericardium derived from?

Somatic mesoderm

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What is the visceral layer of the serous pericardium derived from?

Splanchnic mesoderm

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Where does the pericardial cavity go from and to after cranial folding?

Dorsal to ventral

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Where does the cardiac tube go from and to during cranial folding?

Ventral to dorsal

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What are the two ends of the primitive heart tube?

Cranial end (arterial)

Caudal end (venous)

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What is 1?

Trancus arteriosus

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What is 2?

Bulbus cordis

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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?

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