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Questions and Answers
What initiates the formation of the primitive heart tube?
What initiates the formation of the primitive heart tube?
What is the connection between septum primum and septum secundum?
What is the connection between septum primum and septum secundum?
What adult structure derives from the bulbus cordis?
What adult structure derives from the bulbus cordis?
What is the purpose of the foramen ovale during fetal development?
What is the purpose of the foramen ovale during fetal development?
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Which structure is formed during the partitioning of the bulbus cordis and truncus arteriosus?
Which structure is formed during the partitioning of the bulbus cordis and truncus arteriosus?
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What distinguishes the muscular septum from the membranous septum?
What distinguishes the muscular septum from the membranous septum?
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What occurs between the two ventricles during the early stages of heart development?
What occurs between the two ventricles during the early stages of heart development?
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What embryological structure contributes to the formation of the endocardial cushions?
What embryological structure contributes to the formation of the endocardial cushions?
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What is the consequence of uncorrected ventricular septal defects (VSD)?
What is the consequence of uncorrected ventricular septal defects (VSD)?
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What is the primary role of the ductus arteriosus in fetal circulation?
What is the primary role of the ductus arteriosus in fetal circulation?
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Which embryonic veins primarily drain the gastrointestinal tract?
Which embryonic veins primarily drain the gastrointestinal tract?
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What do over-riding aorta and pulmonary trunk anomalies result from?
What do over-riding aorta and pulmonary trunk anomalies result from?
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What is the primary source of blood cells during the early embryonic stage?
What is the primary source of blood cells during the early embryonic stage?
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Which aortic arch remains connected to the dorsal aorta after regression?
Which aortic arch remains connected to the dorsal aorta after regression?
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What happens to the ductus venosus after birth?
What happens to the ductus venosus after birth?
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Which condition is characterized by the failure of the ductus arteriosus to close after birth?
Which condition is characterized by the failure of the ductus arteriosus to close after birth?
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What two embryonic veins contribute to the formation of the inferior vena cava?
What two embryonic veins contribute to the formation of the inferior vena cava?
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What results from a localized narrowing of the aorta in the region of the ductus arteriosus?
What results from a localized narrowing of the aorta in the region of the ductus arteriosus?
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Which embryonic venous system is responsible for carrying oxygenated blood from the placenta?
Which embryonic venous system is responsible for carrying oxygenated blood from the placenta?
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What structural anomaly occurs when there is a failure of the truncus arteriosus to divide properly?
What structural anomaly occurs when there is a failure of the truncus arteriosus to divide properly?
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What does the left 6th aortic arch develop into during maturation?
What does the left 6th aortic arch develop into during maturation?
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Study Notes
Primitive Heart Tube Formation
- Angiogenic cell clusters develop beside the developing pericardial cavities.
- Lateral folding brings endocardial heart tubes to the midline, where they fuse.
- The dorsal mesocardium breaks down, suspending the heart tube in the pericardial cavity.
Primitive Heart Tube Parts & Adult Derivatives
- Sinus Venosus: Coronary sinus
- Endocardial Cushions: Membranous ventricular septum
- Bulbus Cordis: Ventricles
- Septum Secundum: Atrial septum
- Truncus Arteriosus: Proximal part of aorta
Atrioventricular Canal Formation
- A wedge of endocardial tissue forms, directing blood flow.
Atrial Septum Formation
- Two-phase process (pre- and post-birth).
- Septum Primum: Grows from the atrium roof; foramen primum is the opening below. Develops perforations as it grows.
- Reaches endocardial cushions, some portions disappear, creating foramen secundum.
- Septum Secundum: Begins to grow on the right side, overlaps septum primum.
- Foramen ovale is the path between the two septa.
Foramen Ovale's Fetal Role
- Allows blood flow between atria before birth.
Aorta and Pulmonary Trunk Formation
- Aorticopulmonary Septum: Forms in a spiral, dividing bulbus cordis and truncus arteriosus into aorta and pulmonary trunk.
- Neural crest cells are involved.
Interventricular Septum Formation
- Two parts: Muscular and membranous.
- Muscular: Outgrowth of ventricular floor; cells from bulbus cordis and primitive ventricle proliferate.
- Membranous: Right and left bulbar/truncal ridges and endocardial cushions fuse with muscular septum, creating separate blood flows.
Primitive Heart Tube Blood Flow and Changes
- Open communication between ventricles until week 7 (interventricular foramen).
- Changes occur when heart septa form.
Atrial and Ventricular Septal Defects (Etiology)
-
Ventricular Septal Defects (VSD):
- Membranous (common) or muscular (rare).
- Normally, blood flows left-to-right with normal blood pressure.
- However, increased oxygenated blood can cause issues elsewhere, the heart works harder, leading to hypertension.
- Uncorrected defects lead to heart failure; small defects may self-correct.
- VSDs often result from aorticopulmonary septum issues.
Great Vessel Anomalies
- Persistent Truncus Arteriosus: Truncus arteriosus fails to divide.
- Transposition of Great Vessels: Aorticopulmonary septum grows straight instead of spiraling.
- Overriding Aorta/Pulmonary Trunk: Unequal truncus division; one artery is larger; misplaced aorticopulmonary septum.
- Tetralogy of Fallot: Four defects occurring together: overriding aorta, VSD, pulmonary stenosis, RV hypertrophy.
Embryonic Vessel Formation
- Extraembryonic vessels: From yolk sac extraembryonic mesoderm, forming a network of angioblastic cells/blood islands. Blood islands become angioblastic cords, then tubes.
- Embryonic vessels: From splanchnic mesoderm, forming blood islands that infiltrate all layers. Blood islands become cords, then vessels.
Blood Cell Sources
- Yolk sac initially supplies blood cells.
- Later, liver, spleen, thymus, and eventually bone marrow are sources.
Embryonic Aortic Arch System Changes
- Arches 1 and 2 largely regress; arch 5 disappears.
- Arch 3 supplies head; arches 4 and 6 supply trunk.
- Arch 3: forms internal and common carotids.
- Arch 4: forms parts of aortic arch and subclavian artery.
- Arch 6: forms parts of pulmonary arteries and ductus arteriosus.
Ductus Arteriosus Origin and Role
- From the distal portion of the 6th arch.
- Important for fetal arterial compensation.
Major Arterial Derivatives of Dorsal Aorta
- Intersegmental arteries (vertebral, intercostal, etc.).
- Ventral branches (vitelline and umbilical arteries).
- Lateral branches (renal, suprarenal, gonadal).
Arterial Anomalies (PDA, Double Aortic Arch, Aortic Coarctation)
- Patent Ductus Arteriosus (PDA): Failure of DA to close; higher left pressure shunts blood to pulmonary arteries.
- Coarctation of the aorta: Localized narrowing of the aorta near the DA.
- Double Aortic Arch: Abnormal persistence of right dorsal aorta.
Embryonic Venous Systems
- Umbilical: Oxygenated blood from placenta.
- Vitelline: Drains yolk sac, then GI tract.
- Cardinal: Three pairs carrying blood from the embryo; anterior and posterior cardinals drain into common cardinals.
Vitelline and Umbilical Vein Transformations
- Vitelline veins: Form a plexus around the gut, contributes to portal vein system.
- Umbilical veins: Bypass liver and connect with vitelline veins. Right umbilical vein degenerates. Left umbilical vein forms anastomosis with ductus venosus.
Ductus Venosus Development and Fetal Role
- Forms anastomosis with left umbilical vein.
- Shunts half the oxygenated blood from umbilical vein to right atrium via inferior vena cava.
Embryonic Veins Contributing to Inferior Vena Cava
- Superior right vitelline vein forms part of the inferior vena cava.
Fetal Circulation (Umbilical Vein to...)
- Umbilical vein, ductus venosus, inferior vena cava, right atrium, foramen ovale, left atrium, left ventricle, aorta, systemic circulation, umbilical arteries.
Fetal vs. Postnatal Circulation Differences
- After birth, ductus arteriosus constricts; blood goes to the lungs.
- Foramen ovale closes (fossa ovalis); inferior vena cava carries deoxygenated blood.
- Ductus venosus degenerates (ligamentum venosum).
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Description
Explore the intricate processes of primitive heart tube formation and the development of key structures such as the atrioventricular canal and atrial septum. This quiz covers essential embryological concepts and their adult heart derivatives. Test your knowledge on how these structures contribute to heart anatomy.
