Heart Dev little cute things idk Flashcards
What is the first major organ to develop in an embryo?
The heart
The heart develops first to supply oxygen and nutrients to the growing embryo.
What are the main stages of heart development?
- Cardiogenic specification
- Folding
- Heart tube formation
- Cardiac looping
- Septation
- Valve formation
- Trabeculation
- Great vessels
Stages of heart development overlap and do not occur in a segregated manner.
Define morphogenesis in the context of heart development.
Cells form the shape and physical structure of the organ
Involves cell proliferation, differentiation, migration, and apoptosis.
What are the key processes involved in morphogenesis?
- Cell proliferation
- Differentiation
- Cell migration
- Extracellular matrix deposition and remodeling
- Tissue folding and convergence
- Apoptosis
These processes help refine the shape of the developing heart.
Which mesodermal layer is responsible for cardiogenic specification?
Splanchnic mesoderm
It develops into the heart tube.
What are the two overlapping regions of cardiogenic mesoderm?
- First heart field
- Second heart field
The first heart field is medial to the second heart field.
What genes specify cardiogenic progenitors in the first heart field?
- Nkx2.5
- Gata4
- Tbx Family (Tbx5)
- FGF8
- SHH
These genes are crucial for the differentiation of heart structures.
What is the role of morphogen gradients in heart development?
They provide precise spatial and temporal regulation of gene expression
Morphogen gradients help specify cell differentiation locations.
What factors regulate looping and chamber specification in heart development?
- Morphogen gradients
- Tbx5
- Irx4
- Retinoic acid
These factors alone and in combination specify heart tube regions and looping.
True or False: Septation occurs after the formation of heart chambers.
False
Septation happens first across the middle to create left and right sides.
What is the significance of epithelial-mesenchymal transition (EMT) in heart development?
It allows cells to migrate to form structures like endocardial cushions
EMT is crucial for the formation of the septa and valves.
Fill in the blank: The embryonic heartbeat can be detected using ______ during the 4th week.
Doppler ultrasonography
This technology allows for the detection of the heartbeat as early as Day 24.
What is the function of the cardiac jelly during heart development?
It supports cell migration, proliferation, and differentiation
Cardiac jelly is secreted by myoblasts in the myocardium.
What is the role of apoptosis in heart morphogenesis?
To remove unnecessary cells for shape refinement
Apoptosis is a critical process for the proper development of heart structures.
What is the structure formed by the fusion of heart tubes?
Epicardium
The epicardium develops from the fusion of the heart tubes.
What are the two main components that contribute to the endocardial cushions?
- Endocardial cells
- Neural crest cells
Both cell types undergo EMT to form the cushions necessary for septation.
Identify the main stages and processes involved in the development of the cardiovascular system.
- Cardiogenic mesoderm formation
- Heart formation stages
- Contribution of multiple cell lineages
Understanding these stages is essential for studying heart development.
Major Stages of Heart Development
Cardiogenic Specification (Day 18)
The mesoderm layer forms a specialized region called the cardiogenic mesoderm, which will develop into the heart.
This happens cranially (toward the head) from the primitive node.
Heart Tube Formation (Days 20-22)
Lateral folding of the embryo brings two heart fields together, forming a single heart tube.
Blood starts flowing in a peristaltic wave (like squeezing a tube of toothpaste).
Cardiac Looping (Days 23-28)
The heart tube twists and folds into an “S” shape.
Rightward (D-looping) movement positions the chambers in the correct locations.
Septation (Days 28-37)
The heart is initially a single tube, but it separates into four chambers.
Epithelial-Mesenchymal Transition (EMT) is crucial for forming the atrioventricular septum (wall between atria & ventricles).
Valve Formation & Trabeculation
Valves form from endocardial cushions.
The heart starts forming trabeculae (muscular ridges) inside ventricles.
What Regulates Heart Development?
Morphogens (signaling molecules)
BMP2, BMP4, TGFβ, Activin = Promote heart cell differentiation
Wnt (inhibits heart formation) is blocked by Noggin & Chordin (from the notochord)
Nkx2.5, Gata4, Tbx5 = Control heart field formation
Left-Right Specification
Nodal & Pitx2 = Determine left-sided development
FGF8 (on right side) inhibits Pitx2 → Ensures correct heart orientation
Mechanical Forces
Blood flow influences valve formation and heart chamber growth.
Heart Fields & What They Become
Heart Field Future Structures
1st Heart Field Left ventricle, atria, aorta
2nd Heart Field Right ventricle, outflow tract, atrial septum
Key Events During Septation
Left & Right Separation: Endocardial cushions divide atria and ventricles.
Endocardial cushions form in the atrioventricular (AV) canal
These cushions grow toward each other and fuse to:
Divide the common AV canal into right and left AV orifices (→ tricuspid and mitral valves)
Provide a foundation for the atrial septum and ventricular septum
So they’re basically the “scaffolding” for dividing the heart into left and right sides.
Foramen Ovale Formation: A hole in the septum allows fetal circulation.
Septum primum and septum secundum grow toward the endocardial cushions
They form a flap-like hole between the right and left atria: the foramen ovale
Purpose? Allows oxygenated blood from the placenta (via the IVC) to bypass the non-functional fetal lungs
After birth: Foramen ovale closes and becomes the fossa ovalis
Neural Crest Cells (NCCs) contribute to outflow tract and septum formation.
Neural crest cells migrate into the outflow tract of the heart
They help form the aorticopulmonary septum, which divides:
The truncus arteriosus into the aorta and pulmonary artery
This is essential for separating systemic and pulmonary circulation
Q: What are the key stages of heart development?
A: Cardiogenic specification → Heart tube formation → Looping → Septation → Valve formation.
Q: What structure does the 1st heart field form?
A: Left ventricle, atria, aorta.
Q: What structure does the 2nd heart field form?
A: Right ventricle, outflow tract, atrial septum.
Q: What molecular signals are important for heart field formation?
A: Nkx2.5, Gata4, Tbx5, BMP2, BMP4.
Q: What determines left-right symmetry in the heart?
A: Nodal, Pitx2 (left), FGF8 (right).
Q: When does the heart start beating?
A: Day 24.
