congenital heartdiseasekazucardioembryology
TRANSCRIPT
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Cardiovascular Embryology
Kazuhito MoriInternal Medicine Group-1
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Plait du Jour / Today’s Menu• Cardiac Development;– General Cardiobiology– From Zygote to the Heart Tube– Heart Tube-I: Early Development– Heart Tube-II: Looping– Heart Tube-II: Septation– Conductive System & Valves– Summary Notes: For Your Self-Study
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General Cardiobiology1. The Heart is the 1st organ to form within the embryo2. Developmental abnormalities affect 8-10 of every 1000 births in US.3. Cardiac developmental process begins during the 4th week. [Day 22-28th]4. Early progenitors arise within crescent-shaped Lateral Splanchnic
MESODERM.5. Signals from Neural Ectoderm influence the process before Neural Tube
closure.6. The precursors express Regulatory Transcription Factors; NKX2-5 or GATA47. Mutations of those will lead to the Inherited Congenital Heart Disease.
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Zygote to Heart Tube
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Zygote to Heart Tube
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Zygote to Heart Tube
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Heart Tube-I: Early Development1) Early cardiac precursors form 2 Bilateral Heart Tubes
1) A single layer of Endocardium2) A single layer of Myocardial Precursors that surround
the above.2) A single midline Heart Tube formed by
1) The Medial Migration2) The Midline Fusion of 2 Structures
3) A single layer of Myocardial cells secrete “Cardiac Jelly”1) Extracellular Matrix rich in Hyaluronic Acid2) Accumulated within Endocardial Cushions3) Endocardial Cushions are precursor for Heart Valves
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Heart Tube-I: Early Development
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Heart Tube-I: Early Development
• Week 2 – 3: pair of thin-walled tubes• Week 3: paired Heart Tubes fuse, Truncus Arteriosus outflow, Heart contracting• Week 4: Heart Tube continues to elongate, curving to form S shape• Week 5: Septation starts; Atrial & Ventricular
– Septation continues, Atrial Septa remains open, Foramen Ovale
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Heart Tube-I: Early Development
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Corresponding Structures• Truncus Arteriosus
– Ascending Aorta– Pulmonary Trunk
• Bulbus Cordis– Left Ventricle– Right Ventricle
• Primitive Ventricle– Trabeculated Ventricle
• Primitive Atrium– Trabeculated Atrium
• Right Horn of SV– Smooth Part of RA
• Left Horn of SV– Coronary Sinus
Heart Tube-I: Early Development
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Heart Tube-II: Looping
1) Looping is coordinated with chamber specification2) Balooning of various regions produce the presumptive Atria & Ventricles3) Significant portion of Right Ventricle formed by addition of Second Heart Field 4) Second Heart Field migrated from Ventral Pharynx5) Islet-1 is a marker to identify, expressed in the field6) SEPTATION follows Looping & Chamber specification7) Aorta & Pulmonary arteries formed from Truncus Arteriosus
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Heart Tube-III: Septation General
1) Septum Primum grows toward Endocardial Cushion [Foramen Primum inbtw]2) Septum Primum perforates to be Foramen Secundum3) Foramen Secundum=Right-to-Left-Shunt, Septum Secundum grows4) Septum Secundum contains permanent opening, Foramen Ovale5) Upper Septum Primum degenerates, Lower remains; Valve of Foramen Ovale
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Heart Tube-III: Septation 11) Septum Primum
appears & grows toward Endocardial Cushion
2) Foramen Primum is the hole located between Septum Primum & Endocardial Cushion
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Heart Tube-III: Septation 21) Septum Primum
perforates 2) Perfortation is called
Foramen Secundum
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Heart Tube-III: Septation 31) Foramen Secundum
functions as Right-to-Left-Shunt
2) Septum Secundum grows from the upper part
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Heart Tube-III: Septation 41) Septum Secundum
elongates2) Septum Secundum
contains permanent opening
3) Permanent Opening is called Foramen Ovale
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Heart Tube-III: Septation 5• Upper Septum Primum
degenerates• Lower Septum Primum
remains• Lower Septum Primum
is called Valve of Foramen Ovale
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Conductive System & Valves
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• Slow (Proximal) Components– Sinoatrial (SA) Node --- Sinus Venosus– Atrioventriuclar (AV) Node --- AV Canal
• Fast (Distal) Components --- Myocardial Cells– His Bundle– Bundle Branches– Purkinje Fibres
• Gap Junction Proteins (Connexins) & Ion Channels will determine Slow or Fast• Congenital Heart Block & Preexcitation Syndromes --- Wolff-Parkinson-White Synd.
Conductive System & Valves
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Note: General & Early Stage1. The Heart is the 1st organ to form within the embryo2. Developmental abnormalities affect 8-10 of every 1000 births in US.3. Cardiac developmental process begins during the 4th week. [Day 22-28th]4. Early progenitors arise within crescent-shaped Lateral Splanchnic MESODERM.5. The precursors express Regulatory Transcription Factors; NKX2-5 or GATA4,
mutation leads to CHD.6. Formed initially in Lateral splanchnic Mesoderm of prechordal plate region -
Cardiogenic Region7. Growth & folding of the embryo moves Heart ventrally & downward into
Anatomical Position8. Week 2 – 3: pair of thin-walled tubes, 2 Bilateral Layers9. Week 3: paired Heart Tubes fuse, Truncus Arteriosus outflow, Heart contracting10. Day 22 - 23, begins to beat in humans
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Note: Looping1. Week 4: Heart Tube continues to elongate, curving to form S shape2. Looping is coordinated with chamber specification3. Balooning of various regions produce the presumptive Atria & Ventricles4. Significant portion of Right Ventricle formed by addition of Second Heart Field 5. Second Heart Field migrated from Ventral Pharynx6. Islet-1 is a marker to identify, expressed in the field7. SEPTATION follows Looping & Chamber specification8. Aorta & Pulmonary arteries formed from Truncus Arteriosus
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Note: Septation1. Week 5: Septation starts, Atrial & Ventricular2. Septum Primum grows toward Endocardial Cushion [Foramen Primum inbtw]3. Septum Primum perforates to be Foramen Secundum4. Foramen Secundum=Right-to-Left-Shunt, Septum Secundum grows5. Septum Secundum contains permanent opening, Foramen Ovale6. Upper Septum Primum degenerates, Lower remains; Valve of Foramen Ovale7. Septation continues, atrial septa remains open, foramen ovale8. Week 37-38: At birth, pressure difference closes foramen ovale leaving a fossa
ovalis
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Note: Conductive System1. Slow (Proximal) Components
1. Sinoatrial (SA) Node --- Sinus Venosus2. Atrioventriuclar (AV) Node --- AV Canal
2. Fast (Distal) Components --- Myocardial Cells1. His Bundle2. Bundle Branches3. Purkinje Fibres
3. Gap Junction Proteins (Connexins) & Ion Channels will determine Slow or Fast4. Congenital Heart Block & Preexcitation Syndromes --- Wolff-Parkinson-White
Synd.