Cardiology embryology Flashcards by David Brennan

List the 5 main stages in heart development

Bilateral heart primordia
Primitive heart tube
Heart looping
Atrial + ventricular septation
Outflow tract septation

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During what week does the CVS first function?

Week 4

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Why is the CVS one of the first systems to be formed?

The nutrition by diffusion is not sufficient to satisfy the rapidly growing embryo

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What 3 things occur in week 3

Blood vessels (islands) first appear in the yolk sac, allantois, connecting stalk and chorion
Blood vessels in lateral plate spachnich mesoderm form 2 heart tubes
Heart tubes fuse and join blood vessels in other areas to form primordial CVS

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What are blood vessel ‘islands’ known as

Cardiogenic field

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Why does the heart tube come to lie dorsal to the pericardial cavity?

Due to crainial folding of embryo

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What forms the parietal serous pericardium and the fibrous pericardium?

The somatic mesoderm

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What forms the visceral serous pericardium?

The splachnic mesoderm

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What forms the pericardial cavity?

The intraembolic coelom

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What are the 5 parts of the primitive heart tube

Primitive atira
Primitive ventricles
Bulbus cordis
Sinus venosis
Truncus arteriosis

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Why does the cardiac loop form?

As the primitive heart tube invaginates the pericardium. And the growing tube becomes too large for the pericardium and so needs to fold/loop

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Describe the fomration of the cardiac (bulboventricular) loop

Bulbus cordis + ventricle enlarge and loop to the right
The ventricle is pushed to the left and inferiorly
Atria pushed superiorly and posteriorly

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Describe dextrocardia

Abnormal cardiac looping
Heart tube loops to the left side instead of the right, so ventricles come to lei facing the right (=dextro)
Most frequent positional abnormality of the heart

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How are the left and right atrioventricular canals formed?

Via endocardial cushion growth that separates the Right atrium and ventricle from the left atrium and ventricle to form L + R AV canals

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Describe the 1st step of the partitioning of the primitive atrium into the left and right atria

Formation of septum primum and osium primum

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Describe the 2nd step of the partitioning of the primitive atrium into the left and right atria

Ostium secundum begins to form by apoptosis of part of the septum primum

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Describe the 3rd step of the partitioning of the primitive atrium into the left and right atria

Formation of the ostium secundum is complete, formation of the septum secundum, closure of ostium primum as septum primum meets endocardial cushions

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Describe the 4th step of the partitioning of the primitive atrium into the left and right atria

Formation of foramen ovale complete

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What does septum mean?

Tissue

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What does ostium mean?

Gap/space

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Define the foramen ovale

The opening between the right and left atria that is present until birth

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What is the role of the foreamen ovale before birth?

One way shunt allowing most of the blood to pass from the RA to LA (bypassing non-functioning lung), prevents passage of blood in opposite direction

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What happens to the foramen ovale after birth?

Normally closes (increase pressure in LA due to increased pul circ at first breath)

Septum primum fuses with septum secundum
Fossa ovalis (depression in interatrial septum) of adult heart is reminent of foetal foreamen ovale

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What does non-closeure of foramen ovale cause?

Result in patent foramen ovale (PFO) - a common form of congenital atrial septal defect (ASD) otherwise known as a hole in the heart

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Describe the partitioning of the primitive ventricle

1. Muscular ventricular septum forms | 2. Aorticopulmonary septum divides bulbis cordis + truncus artiorosis into aorta + pulmonary trunk

What is the name of the opening when muscular ventricular septum forms?

Interventricular foramen

How is the interventricular foramen closed?

Bottom of spiarl aorticopulmonary septum fuses with muscular ventricular septum + endocardial cushions to form membraneous interventricular septum, closing interventricular foramen

What is the most common type of congenital heart disease?

Ventricular septal defect

What % of congenital heart disease is ventricular septal defect?

25%

Describe ventricular septal defect

Can appear in any part of septum, small VSDs close spontaneously

What % of VSD close spontaneously?

30-50%

What is the most common type of VSD?

Membranous

What is the role of the aorticopulmonary septum

Divides bulbus cordis + truncus arteriosis into aorta and pulmonary trunk (spiral)

Describe the transpotision of the great vessels

Aorta leves RV, pul trunk leaves LV

What does transposition of great vessels typically cause in newborn infants?

Cyanotic disease

What is transposition of great vessels typically associated with?

ASD + VSD (which would permit exchange of systemic and pulmonary circulation)

Describe the cause of transposition of the great vessels

1. Failure of aorticopulmonary septum to take a spiral course 2. Defective migration of neural crest cells to heart

What are SL valves formed from?

Subendocardial valve tissue

What are the early pacemakers?

Cardiomyocytes in primitive atrium and sinus venosus

When does the SA node develop?

5th week

What forms the AV node and the bundle of his?

Develops from cells of AV canal + sinus venosus

What is formed from the aortic sac/truncus arteriosis?

Aortic arches

What is formed from the bulbus cordis?

RV and parts of the outflow tracts

What is formed from the primitive ventricle?

What is formed form the primitive atrium?

Parts of RA and LA

What is formed form the sinus venosis

SVC and RA

What are the first arteries to appear in the embryo?

R and L primitive aortae

Describe the primitive aorta

Each aorta has a ventral and dorsal part (ventral and dorsal aorta)

how is the aortic sac formed?

Formed by fusion of the 2 ventral aorta (aka aortic sac gives rise to ventral aorta) aortic sac then becomes extension of truncus arteriosus

When do the aortic arches form?

4th and 5th weeks

how many pairs of aortic arches are formed?

What are aortic arches formed from?

Aortic sac (then unite with dorsal aorta)

What do aortic arches eventually form?

The great arteries of the neck and head

What are the 2 methods of blood vessel development

Vasculogenesis and angiogenesis

Define vasculogenesis

New formation of a primitive vascular network

Dfine angiogenesis

Growth of new vessels from pre-existing blood vessels

what happens to the first aortic arch?

Dissapears early

What happens to the 2nd arotic arch?

Dissapears early

What happens to the 3rd aortic arch?

Forms common carotid artery

What happens to the 4th right aortic arch?

Forms subclavian artery

What happens to the 4th left aortic arch?

Forms aortic arch

What happens to the 5th aortic arch?

Dissapears

What happens to the 6th right aortic arch?

Forms right pulmonary artery

What happens to the 6th left aortic arch

Forms left pulmonary artery and ductus arteriosis

What are 2 methods by which arotic arch abnormalities can form?

persistence of arches that normally regress | Progression of arches that normally persist

What is an example of an aortic arch abnormality?

Right subclavian artery sometimes has abnormal origin on the Left which may constrict trachea and oesophagus

Define a patent ductus arteriorsus

Ductus arteriosis should close off and become ligamentous. In this patient it did not close off

What is a common cause of patent ductus arteriosus?

Associated with maternal rubella infection in early pregnancy

What are the causes of patent ductus arteriosis?

Failure of muscular wall to contract respiratory distress syndrome Lack of surfactant in the lungs

What can an uncorrected PDA cause?

Congestive heart failure with increasing age

What other defects is PDA associated with?

ASD, VSA and coartication of the aorta

Define coartication of the aorta

Congenital condition where aorta is narrowed, usually when ductus arteriosus (ligamentous arteriosum) inserts - Most common in aortic arch

Define preductal and post ductal coartication of the aorta

``` Pre-ductal = proximal to ductus arteriosus Post-ductal = distal to ductus arteriosus ```

List the 2 main theories of cause of coartication of aorta

When ductus arteriosus contracts after birth, part of attached arch also constricts or genetics/environmental

What does the viteline vessel supply?

Yolk sac

What does the viteline vessel turn into in adults?

Adult gut vessels

What does the umbilical vessel supply?

The placenta

What does the umbilical vessel turn into in adults?

Internal iliac

What do the cardinal vessels supply?

Rest of the body

What do the cardinal vessels turn into in adults?

SVC + IVC

When does the lymphatic system develop?

End of 6th week

What first develops regarding the lymphatic system?

6 primary lymph sacs develop at end of embryonic period, lymphatic vessels will later join

What does the thoracic duct develop from?

2 Vessels anterior to aorta become L + R embryonic thoracic ducts

What does the L embryonic thoracic duct give rise to in adults?

1/3 of the adult thoracic duct

What does the R embryonic thoracic duct give rise to in adults?

2/3 of adult thoracic duct

What organs does the placenta 'replace' in the foetus?

Lungs + kidney

Describe foetal circulation

Oxygenated blood from the placenta reaches foetal IVC, via the umbilical veins, mostly by bypassing foetal liveer Foetal blood in IVC = Mixed oxygenated + deoxygenated

Name 3 foetal circulation shunts

1. Ductus venosus 2. Foramen ovale 3. Ductus arteriosus

Describe the ductus venosus

Shunts in L umbilical vein to IVC (allows oxygenated blood from placenta to bypass liver)

Describe the ductus arteriosus

Shunts blood from the RV and pulmonary arteries to the aorta (allows blood to bypass lungs)

What does the ductus venosus turn into?

Ligamentum venosum of the liver

What does the ductus arteriosus turn into?

Ligamentum arteriosum between the L pul artery and the aorta

What do the umbilical arteries turn into?

Medial umbilical ligaments of the anterior abdominal wall