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Flashcards in Cardiac Embryology Deck (36)
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In what direction does the heart rotate during embryological development/



Label the structures on the diagram 


Where do blood vessels develop?

At what stage of development is this embryo?

What do the umbilical vessels communicate with?

Label the blood vessels on the diagram 

In the extraembryonic mesoderm 

Week 3

Umbilical vessels communicate with:

  • Developing fetal circulation
  • Developing placenta 


Label the features on the cardiac mesoderm 

At what stage of development is this embryo?

What are angiogenic cell clusters?

Angiogenic cell clusters are collections of angiogenic cells which are developing into blood vessels. 

  • Form paired angiogenic cords
  • Cords canalise to form paired endochondral heart tubes 

Embryo in image is in week 3 of development 


When does the embyronic heart begin beating?

When does blood flow begin?

Heart starts beating day 22-23

Blood flow begins week 4



What is the role of neural crest cells?

Neural crest cells from the developing brain and spinal cord migrate away from the developing central nervous system.

Involved in the development of parts of the heart 


Label the structures on the embryonic disc 

Where is the heart tube?


What occurs during longitudinal folding?

The brain, mouth and heart are moved into 'adult' position:

  • The brain develops quickly and pushes itself above the mouth region



What does the septum transversum become?

Fibrous pericardium and part of diaphragm 


What happens to the paired heart tubes during lateral folding?

They are brought together and fuse in the midline to form a large singular tube 

Venous inflow enters and flows through the tube into the aortic arches 


Where do the aortic arches sit?

Pharyngeal arches 


What anchors the developing heart tube to the future diaphragm (septum transversum) 

Label the developing structures on the diagram 

Vitelline veins 


What do the dilations of the heart tube become?

Label them on the diagram 

Bulbus cordis

  • = aortic vestibule of left ventricle 
  • = conus arteriosis of left ventricle 

Truncus arteriosus

  • = Ascending aorta
  • = Pulmonary truk


  • = trabecular walls of left and right ventricles


  • = auricles/pectinate walls of left and right atria 

Sinus venosus

  • = Coronary sinus
  • = Smooth wall of right atrium 


How does the heart tube split to form right and left sides of the heart?

  • Endocardial cushion develops and grows into a septum separating the heart tube into 2 sections longitudinally 


What develops from the future left atrium section of the heart tube?

Pulmonary veins 


Where are the rough atrial walls derived from embryologically?

What are the smooth walls formed from?

Rough atrial walls: embryological atrium

Right smooth atrial wall: right horn of the venous sinus 

Left smooth atrial wall: formed from its growth into the pulmonary veins 




What causes the heart tube to fold?

Describe this process


Folds due to the fixed position of the aortic arches and venous input.

  • Bulbus cordis grows quickly and moves infero-anteriorly to the right 



Describe the vascular shunts in the embryonic heart 

Right to left shunts exist to bypass the lungs which are not fully developed. 

Shunt between right and left atria

Shunt between pulmonary trunk and aorta 


How does dextrocardia occur?

What is it?

Dextrocardia= adult heart on the right side instead of left. 

Occurs when bulbus cordis folds to the left and ventricles form to the right 


How are the developing atria connected to the ventricles?

Via the atrioventricular canal 


Where do the bicuspid and mitral valves grow?

Within the atroventricular canal 


How is the atrioventricular canal separated?

By endocardial cushions that grow from anterior to posterior and meet in the middle to separate right and left AV canals 


How does atrial septation occur?

  1. Septum primum develops and grows towards endocardial cushion. 
  2. Before it reaches the cushion, holes form (foramen secondum)- this maintains right to left shunt.
  3. Muscular septum secondum then grows towards cushion
  4. This forms the foramen ovale through which blood is shunted right to left. 



Describe the pressure differences in the right and left sides of the heart in utero compared to a neonate. 

Why is there a difference?

In utero:

  • High pressure right side of heart
  • Lower pressure in left side of heart
  • Due to:
    • Lungs filled with fluid
    • High pulmonary vascular resistance
    • More blood is entering the right atrium than the left
    • Blood shunted through foramen ovale 


  • Lower right sided pressure than left
  • Due to:
    • Lungs drained and functional
    • Low pulmonary vascular resistance
    • Greater pulmonary blood flow
    • More blood in left atrium
    • Valve of foramen ovale closes on first breath


When do tissues of the foramen ovale fuse?

What is it called when they don't properly fuse? When can this be a problem?

How can this defect be detected?

Usually fuse several months after birth

Failure to properly fuse = probe-patient foramen ovale

Can become a problem in situations where right sided heart pressure increases over left- for example during the valsalva manouvre 

  • Increases possibility of TIA and stroke (clots in the right side can be pushed over to the left and enter the systemic circulation)

Microbubble test is used to detect defects (ultrasound)


Where can atrial septal defects form?

Are they always symptomatic?


  • In the septum/foramen primum
  • In the septum/foramen secondum
  • In the endocardial cushion

Some symptomatic, some not

Some close during growth without the need for surgical intervention 


In what direction would the blood be shunted in an atrial septal defect after birth?

Why is a small atrial septal defect not a cyanotic congenital cardiac defect?

Left to right (pressure in left side higher after birth than right)

Cyanosis woud not occur as blood shunted would be re-circulated around the lungs 


How does ventricular septation occur?

Ventricular septum grows towards endocardial cushion from ventricular floor- remains incomplete in upper region 

Completed in the upper (cranial) region by membranous downgrowth of bulbar ridges and endocardial cushion. 

  • Membranous tissue also separates the aorta and pulmonary trunk 


Where do ventricular septal defects most commonly occur?

In the membranous part of the septum 


How is the ventricular outflow separated (into aorta and pulmonary trunk)?

At what stage of embryological development does this occur?

Membranous septum forms in truncus arteriosis and bulbus cordis which spirals (spiral septum) due to the turbulent flow of blood. 

Grows down to meet the muscular part of the ventricular septum