Questions and Answers
When does the heart begin its development?
day 18 or 19 following fertilization
What is the primary heart field (PHF)?
A horseshoe-shaped cluster of cells forming portions of the atria and the entire left ventricle.
What do endocardial cushions do during heart development?
They grow toward each other, fuse, and divide the atrioventricular canal into separate left and right atrioventricular canals.
Which of the following regions does the primitive heart tube develop into? (Select all that apply)
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What is a significant defect caused by atrial septal defect (ASD)?
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Congenital heart defects are only found in males.
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What condition is characterized by the tricuspid valve being displaced toward the apex of the right ventricle?
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What are the two common types of hypoplastic heart syndrome mentioned?
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Which factors contribute to the development of the heart? (Select all that apply)
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Study Notes
Embryology of the Heart
- Heart development begins from mesoderm on day 18 or 19 post-fertilization, with progenitor heart cells migrating to form the primary heart field (PHF).
- The primitive heart tube elongates by day 23, resulting in a loop, mainly due to the rapid growth of the bulbus cordis and primitive ventricle.
- On day 28, endocardial cushions appear within the heart wall, progressing to separate left and right atrioventricular canals from the single canal.
- The interatrial septum starts to develop toward fused endocardial cushions, ultimately forming the foramen ovale.
Structure of the Primitive Heart Tube
- On day 22, the primitive heart tube comprises five regions and initiates blood pumping in the following order:
- Sinus venosus
- Primitive atrium
- Primitive ventricle
- Bulbus cordis
- Truncus arteriosus
Molecular Regulation of Cardiac Development
- Heart formation is induced by signaling from the anterior endoderm, prompting NKX2.5 expression in visceral mesoderm via BMPs 2 and 4.
- The involvement of WNT proteins (3a and 8) must be inhibited as they typically suppress heart development.
- Crescent and Cerberus promote NKX2.5 expression and upregulate fibroblast growth factor 8 (FGF8), essential for cardiac-specific protein development.
Congenital Heart Defects
- Atrial Septal Defect (ASD) occurs at a frequency of 6.4 per 10,000 births, being more prevalent in females (2:1 ratio).
- The ostium secundum defect, a significant type of ASD, leads to a large opening between the left and right atria.
- Causes include excessive cell death and resorption of the septum primum or insufficient development of the septum secundum.
- Hypoplastic right heart syndrome (HRHS) and hypoplastic left heart syndrome are rare defects characterized by underdevelopment of either side of the heart.
- Ebstein Anomaly features a tricuspid valve displaced towards the apex of the right ventricle, causing an enlarged right atrium.
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Description
Explore the key concepts of cardiovascular structures in the thorax, focusing on embryology and the development of the heart. This quiz covers the primitive heart tube elongation and the formation of the cardiac loop. Test your understanding of these essential topics in Module 8.
